title: Sensory level electrical muscle stimulation: effect on markers of muscle injury Effect of Slow-Velocity Lengthening Contractions on Muscle Damage Induced by Fast-Velocity Lengthening Contractions Difference in the Magnitude of Muscle Damage Between Maximal and Submaximal Eccentric Loading Protease supplementation improves muscle function after eccentric exercise. Muscle damage and soreness after endurance exercise of the elbow flexors. The effects of massage on delayed onset muscle soreness. Prior exercise and antioxidant supplementation: effect on oxidative stress and muscle injury Effect of lengthening contraction velocity on muscle damage of the elbow flexors. Response of males and females to high-force eccentric exercise Cellular adaptation to repeated eccentric exercise-induced muscle damage. Repeated Eccentric Exercise Bouts Do Not Exacerbate Muscle Damage and Repair Effects of recovery modes after knee extensor muscles eccentric contractions. Diurnal variation, response to eccentric exercise, and association of inflammatory mediators with muscle damage variables. INFLUENCE OF SURFACE ON MUSCLE DAMAGE AND SORENESS INDUCED BY CONSECUTIVE DROP JUMPS Torque loss induced by repetitive maximal eccentric contractions is marginally influenced by work-to-rest ratio Impact of muscle length during stretch-shortening contractions on real-time and temporal muscle performance measures in rats in vivo. Whole-body vibration and the prevention and treatment of delayed-onset muscle soreness. Potent protective effect conferred by four bouts of low-intensity eccentric exercise. Length-specific impairment of skeletal muscle contractile function after eccentric muscle actions in man. Skeletal muscle collagen content in humans after high-force eccentric contractions. Anatomical and mechanical changes following repetitive eccentric exertions. Exercise-induced muscle damage and the repeated bout effect: evidence for cross transfer The efficacy of ice massage in the treatment of exercise-induced muscle damage. Influence of Pre-Exercise Muscle Temperature on Responses to Eccentric Exercise. Changes in hardness of the human elbow flexor muscles after eccentric exercise Antioxidants do not prevent postexercise peroxidation and may delay muscle recovery. Exercise-induced skeletal muscle damage and adaptation following repeated bouts of eccentric muscle contractions. Dietary apple polyphenols have preventive effects against lengthening contraction-induced muscle injuries. Comparison of eccentric knee extensor muscle actions at two muscle lengths on indices of damage and angle-specific force production in humans. Effects of a 7-day eccentric training period on muscle damage and inflammation. Effects of dietary supplementation with vitamins C and E on muscle function during and after eccentric contractions in humans Effects of Hyperbaric Oxygen on a Human Model of Injury The effects of a repeated bout of eccentric exercise on indices of muscle damage and delayed onset muscle soreness. Influence of previous concentric exercise on eccentric exercise-induced muscle damage. EFFICACY OF PRIOR ECCENTRIC EXERCISE IN ATTENUATING IMPAIRED EXERCISE PERFORMANCE AFTER MUSCLE INJURY IN RESISTANCE TRAINED MEN Warm-up, stretching and massage diminish harmful effects of eccentric exercise. Muscle tenderness and peak torque changes after downhill running following a prior bout of isokinetic eccentric exercise. Electromyographic analysis of exercise resulting in symptoms of muscle damage Length-dependent changes in voluntary activation, maximum voluntary torque and twitch responses after eccentric damage in humans. Hyperbaric oxygen therapy does not affect recovery from delayed onset muscle soreness. The Effects of Repeated Maximal Voluntary Isokinetic Eccentric Exercise on Recovery from Muscle Damage Efficacy of Lower Limb Compression and Combined Treatment of Manual Massage and Lower Limb Compression on Symptoms of Exercise-Induced Muscle Damage in Women Lower limb compression garment improves recovery from exercise-induced muscle damage in young, active females Effect of high dose vitamin C supplementation on muscle soreness, damage, function, and oxidative stress to eccentric exercise. Acute adaptation to low volume eccentric exercise. A light load eccentric exercise confers protection against a subsequent bout of more demanding eccentric exercise. Weakness in Mouse Masticatory Muscles by Repetitive Contractions with Forced Lengthening The magnitude of muscle damage induced by downhill backward walking. PROTECTION AGAINST MUSCLE DAMAGE FOLLOWING FIFTY DROP JUMPS CONFERRED BY TEN DROP JUMPS Damage to the human quadriceps muscle from eccentric exercise and the training effect. A single 10-min bout of cold-water immersion therapy after strenuous plyometric exercise has no beneficial effect on recovery from the symptoms of exercise-induced muscle damage Dehydration and symptoms of delayed-onset muscle soreness in normothermic men. RESPONSES OF ELBOW FLEXORS TO TWO STRENUOUS ECCENTRIC EXERCISE BOUTS SEPARATED BY THREE DAYS Attenuation of contraction-induced skeletal muscle injury by bromelain. Branched-chain amino acid ingestion can ameliorate soreness from eccentric exercise. Sports Massage after Eccentric Exercise Subcellular movement and expression of HSP27, alphaB-crystallin, and HSP70 after two bouts of eccentric exercise in humans. Effects of ibuprofen on exercise-induced muscle soreness and indices of muscle damage. The Effects of Ibuprofen on Delayed Muscle Soreness and Muscular Performance After Eccentric Exercise Effects of a second bout of maximal eccentric exercise on muscle damage and electromyographic activity Short-term beta-hydroxy-beta-methylbutyrate supplementation does not reduce symptoms of eccentric muscle damage. Eccentric exercise, isokinetic muscle torque and delayed onset muscle soreness: the role of reactive oxygen species The Effects of Creatine Supplementation on Exercise‐Induced Muscle Damage Responses of human elbow flexor muscles to electrically stimulated forced lengthening exercise. Caffeines enhancement of maximal voluntary strength and activation in uninjured but not injured muscle. Manipulation of knee extensor force using percutaneous electrical myostimulation during eccentric actions: effects on indices of muscle damage in humans. Effects of antioxidant therapy in women exposed to eccentric exercise. Time Course of Changes in Performance and Inflammatory Responses After Acute Plyometric Exercise Supplementation with a whey protein hydrolysate enhances recovery of muscle force-generating capacity following eccentric exercise. Damage to human muscle from eccentric exercise after training with concentric exercise. Muscle fatigue and pain after eccentric contractions at long and short length. Changes in human skeletal muscle ultrastructure and force production after acute resistance exercise. Leg immersion in warm water, stretch-shortening exercise, and exercise-induced muscle damage. Eccentric exercise-induced muscle damage dissociates the lactate and gas exchange thresholds
abstract: Background : Monophasic high voltage stimulation ( MHVS ) is widely prescribed for the treatment of inflammation associated with muscle injury . However , limited scientific evidence exists to support its purported benefits in humans . Objective : To examine the efficacy of early initiation of MHVS treatment after muscle injury . Methods : In a r and omised , cross over design , 14 men performed repetitive eccentric contractions of the elbow flexor muscles followed by either MHVS or control treatment . MHVS treatments were applied five minutes and 3 , 6 , 24 , 48 , 72 , 96 , and 120 hours after eccentric contractions . Results : MHVS result ed in a significant reduction ( p<0.05 ) in delayed onset muscle soreness 24 hours after eccentric exercise compared with controls . Elbow extension was significantly increased immediately after administration of MHVS compared with controls . No significant differences were observed between MHVS treatment and controls for maximal isometric strength , flexed arm angle , or arm volume . Conclusions : Early and frequent application of MHVS may provide transient relief from delayed onset muscle soreness and short term improvements in range of motion after injurious exercise . However , MHVS treatment may not enhance recovery after muscle injury because of lack of improvements in strength and active range of motion Chapman , DW , Newton , MJ , McGuigan , MR , and Nosaka , K. Effect of slow-velocity lengthening contractions on muscle damage induced by fast-velocity lengthening contractions . J Strength Cond Res 25(1 ) : 211 - 219 , 2011-This study tested the hypothesis that the first exercise bout consisting of slow-velocity ( 30 ° ·s−1 ) maximal lengthening contractions would not affect muscle damage in a subsequent bout consisting of fast-velocity ( 210 ° ·s−1 ) lengthening contractions . Eighteen men were r and omly assigned into either a repeated bout group ( n = 10 ) or control group ( n = 8) . The repeated bout group performed 2 bouts of exercise consisting of 210 maximal lengthening contractions of the elbow flexors separated by 14 days at a velocity of 30 ° ·s−1 for the first and 210 ° ·s−1 for the second bout . The control group performed a single bout of the fast-velocity exercise . Changes in maximal isometric strength , range of motion ( ROM ) , upper-arm circumference , muscle thickness , muscle soreness , serum creatine kinase , and lactate dehydrogenase activities were measured before , immediately after , and 24 to 96 hours after exercise . The repeated bout group showed significantly ( p < 0.05 ) smaller changes in all criterion measures except for muscle soreness after the fast-velocity exercise compared with the control group . A significant ( p < 0.05 ) difference was evident only for ROM between the slow- and fast-velocity bouts of the repeated bout group . These results suggest that slow-velocity exercise  reduced muscle damage induced by fast-velocity exercise , although the reduction was not large This study compared maximal ( MAX-ECC ) and submaximal ( 50%-ECC ) eccentric exercise of the elbow flexors . Untrained male students ( n = 8) performed 3 sets of 10 repetitions of MAX-ECC with one arm and 50%-ECC with the other arm , separated by 4 weeks . In MAX-ECC , the elbow joint was forcibly extended from a flexed ( 90 ° ) to a full-extended position ( 180 ° ) in 3 seconds while producing maximal force . For 50%-ECC , a dumbbell set at 50 % of the maximal isometric strength at 90 ° of the elbow joint was lowered from the flexed to the extended position in 3 seconds . Changes in indicators of muscle damage were compared between the bouts by a 2-way repeated- measures analysis of variance . Changes in isometric strength , range of motion , upper arm circumference , and plasma creatine kinase activity were significantly smaller and the recovery was significantly faster for 50%-ECC compared with MAX-ECC , although the differences in the changes immediately after exercise were small . It appeared that the magnitude of initial muscle damage was similar between the bouts ; however , secondary damage was less after 50%-ECC UNLABELLED Protease supplementation has been purported to reduce the damaging effects of eccentric exercise and accelerate recovery of muscle function , possibly by regulating inflammation . PURPOSE To determine the effectiveness of protease supplementation in attenuating eccentric exercise-induced skeletal muscle damage and inflammation . METHODS After st and ard physical and hemodynamic assessment and fasting venous blood sample s , subjects performed isokinetic extension/flexion of the quadriceps group on a Biodex isokinetic dynamometer at 60 ° ·s(-1 ) , followed by VO2max testing . Subjects were r and omly assigned to consume 5.83 g daily of either a cellulose placebo  ( N = 15 ; 22.27 ± 3.33 yr , 71.17 ± 2.91 inches , 179.4 ± 24.05 lb , 50.55 ± 5.66 mL·kg(-1)·min(-1 ) ) or a proteolytic supplement containing fungal proteases , bromelain , and papain ( N = 14 ; 22.85 ± 5.9 yr , 70.0 ± 2.67 inches , 173.11 ± 29.94 lb , 49.69 ± 6.15 mL·kg(-1)·min(-1 ) ) for a period of 21 d. After the supplementation period , subjects donated blood sample s before performing a 45-min downhill ( -17.5 % ) treadmill protocol at 60 % of VO2max . An additional four blood draws and three muscle function tests were performed during the next 48 h. Blood was analyzed using st and ard hematology and clinical chemistry , enzyme-linked immunosorbent assay , and bead array . Blood data were analyzed using multivariate analysis of variance ( MANOVA ) with repeated measures , whereas Biodex data were analyzed using a MANOVA on % Δ values . RESULTS Significant group differences ( T1-T3 , P = 0.033 ; T1-T4 , P = 0.043 ) and another strong trend ( T1 - 3 h , P = 0.055 ) were observed for flexion ( peak torque % Δ at 60 ° ·s(-1 ) ) indicating higher force production in the protease group . Significant group × time interactions ( P < 0.05 ) were observed , including elevations in circulating eosinophils and basophils in the protease group coinciding with lower levels of serum cyclooxygenase 2 , interleukin 6 , and interleukin 12 in this group . CONCLUSIONS Protease supplementation seems to attenuate muscle strength losses after eccentric exercise by regulating leukocyte activity and inflammation PURPOSE This study investigated changes in indirect markers of muscle damage after  endurance exercise of the elbow flexors  and compared the changes with those after maximal eccentric actions ( Max-ECC ) of the elbow flexors . METHODS Eighteen male students  rhythmically lifted ( 1 s ) and lowered ( 1 s ) a light dumbbell ( 1.1 - 1.8 kg : 9 % of MIF ) in 60 - 180 degrees of elbow joint angle for 2 h ( 2-h Ex ) .  Maximal isometric force ( MIF ) , relaxed ( RANG ) and flexed elbow joint angles ( FANG ) , upper-arm circumference ( CIR ) , muscle soreness ( SOR ) , B-mode ultrasound ( US ) , and plasma creatine kinase ( CK ) activity were assessed before and immediately after , and up to 96 h after exercise . RESULTS All measures were altered significantly ( P < 0.05 ) after 2-h Ex in a similar time course to Max-ECC ; however , changes in RANG , FANG , CIR , US , and CK ( peak : 356 + /- 121 IU.L-1 ) were significantly ( P < 0.05 ) smaller compared with those after Max-ECC . SOR developed immediately after 2-h Ex and peaked 24 - 48 h after exercise . MIF dropped to 44.1 % of the preexercise level , which was significantly ( P < 0.05 ) lower than that after Max-ECC ( 58.1 % ) , immediately postexercise . MIF recovered to 79.8 % at 24 h , and 97.8 % at 96 h postexercise , which was a significantly ( P < 0.05 ) faster recovery compared with that of Max-ECC ( 73.1 % at 96 h ) . CONCLUSION These results showed low-intensity continuous muscle contractions ( 3600 times ) result ed in muscle damage ; however , the magnitude of the muscle damage was less severe , and the recovery was faster compared with 12 maximal eccentric muscle actions OBJECTIVES The purpose of this study was to investigate the physiological and psychological effects of massage on  delayed onset muscle soreness ( DOMS ) . METHODS Eighteen volunteers were r and omly assigned to either a massage or control group . DOMS was induced with six sets of eight maximal eccentric contractions of the right hamstring , which were followed 2 h later by 20 min of massage or sham massage ( control ) . Peak torque and mood were assessed at 2 , 6 , 24 , and 48 h postexercise . Range of motion ( ROM ) and intensity and unpleasantness of soreness were assessed at 6 , 24 , and 48 h postexercise . Neutrophil count was assessed at 6 and 24 h postexercise . RESULTS A two factor ANOVA ( treatment v time ) with repeated measures on the second factor showed no significant treatment differences for peak torque , ROM , neutrophils , unpleasantness of soreness , and mood ( p > 0.05 ) . The intensity of soreness , however , was significantly lower in the massage group relative to the control group at 48 h postexercise ( p < 0.05 ) . CONCLUSIONS Massage administered 2 h after exercise induced muscle injury did not improve hamstring function but did reduce the intensity of soreness 48 h after muscle insult Background Both acute bouts of prior exercise ( preconditioning ) and antioxidant nutrients have been used in an attempt to attenuate muscle injury or oxidative stress in response to  resistance  exercise  .  However , most studies have focused on untrained participants rather than on athletes . The purpose of this work was to determine the independent and combined effects of antioxidant supplementation ( vitamin C + mixed tocopherols/tocotrienols ) and prior eccentric exercise in attenuating markers of skeletal muscle injury and oxidative stress in resistance trained men . Methods Thirty-six men were r and omly assigned to : no prior exercise + placebo ; no prior exercise + antioxidant ; prior exercise + placebo ; prior exercise + antioxidant . Markers of muscle/cell injury ( muscle performance , muscle soreness , C-reactive protein , and creatine kinase activity ) , as well as oxidative stress ( blood protein carbonyls and peroxides ) , were measured before and through 48 hours of exercise recovery . Results No group by time interactions were noted for any variable ( P > 0.05 ) . Time main effects were noted for creatine kinase activity , muscle soreness , maximal isometric force and peak velocity ( P < 0.0001 ) . Protein carbonyls and peroxides were relatively unaffected by exercise . Conclusion There appears to be no independent or combined effect of a prior bout of eccentric exercise or antioxidant supplementation as used here on markers of muscle injury in resistance trained men . Moreover , eccentric exercise as used in the present study results in minimal blood oxidative stress in resistance trained men . Hence , antioxidant supplementation for the purpose of minimizing blood oxidative stress in relation to eccentric exercise appears unnecessary in this population PURPOSE This study investigated the effect of lengthening contraction velocity on exercise-induced muscle damage . METHODS Sixteen men were placed into two groups performing either 30 ( N = 8) or 210 ( N = 8) maximal lengthening contractions of the elbow flexors on an isokinetic dynamometer .  Dominant and nondominant arms were r and omly assigned for a slow-velocity ( S : 30 degrees.s(-1 ) ) or a fast-velocity ( F : 210 degrees.s(-1 ) ) exercise separated by 14 d. Maximal voluntary strength of isometric contractions ( iMVC ) and isokinetic concentric contractions ( cMVC ) , range of motion ( ROM ) , upper-arm circumference , muscle soreness , and serum creatine kinase ( CK ) activity were measured before , immediately after , and 1 - 120 h after exercise . Changes in these measures over time were compared by a two-way repeated- measures ANOVA to examine the effect of velocity in the same number of contractions ( S30 vs F30 ; S210 vs F210 ) or the effect of contraction number at the same velocity ( S30 vs S210 ; F30 vs F210 ) . RESULTS A significant ( P < 0.05 ) interaction effect was evident only for iMVC between S30 and F30 , but it was evident for iMVC , cMVC , ROM , and CK between S210 and F210 . Changes in most of the measures were significantly ( P < 0.05 ) smaller after 30 contractions ( S30 and F30 ) than after 210 contractions ( S210 and F210 ) . CONCLUSION These results suggest that the effect of contraction velocity on the magnitude of muscle damage after 30 contractions is minor ; however , when 210 lengthening contractions were performed , the effect of contraction velocity became conspicuous . It is concluded that fast-velocity lengthening contractions are likely to induce greater muscle damage than slow-velocity contractions ; however , muscle fatigue seems to be a confounding factor for the velocity effect It has previously been shown that females incur less muscle damage than males after strenuous exercise , but limited data are available for humans . To determine possible differences between the sexes in humans , the response to high-force eccentric exercise was examined in a large sample of women ( n = 83 ) and men ( n = 82 ) . The participants performed a bout of eccentric exercise of the elbow flexors consisting of 70 maximal repetitions .  Isometric strength , resting elbow angle and muscle soreness were measured before , immediately after ( except soreness ) and then daily for 7 days after exercise . There was a significant loss in strength among both groups ( 69 % for women and 63 % for men ) ( P≪0.01 ) immediately after exercise ; at 168 h post-exercise , women still had a 27 % strength loss and men had a 24 % strength loss . No significant difference in strength loss or recovery rate was found between men and women . Soreness reached peak values 32 - 48 h post-exercise ( P≪0.01 ) , with no significant difference between men and women . Range of motion decreased significantly until 3 days after exercise ( 14.6 ° or 0.255 rad loss for women ; 12.2 ° or 0.213 rad loss for men ) ( P≪0.01 ) ; at 168 h post-exercise , the women and men still showed a loss of 4.8 ° ( 0.084 rad ) and 4.0 ° ( 0.07 rad ) , respectively . There was a significant interaction of sex x time ( P≪0.01 ) ; a post-hoc test indicated that the women experienced a greater loss in range of motion at 72 h than men and this difference was maintained to 168 h post-exercise ( P≪0.01 ) . Thus , our results do not support the contention that women have a lower response to eccentric exercise than men Eccentrically biased exercise results in skeletal muscle damage and stimulates adaptations in muscle , whereby indexes of damage are attenuated when the exercise is repeated . We hypothesized that changes in ultrastructural damage , inflammatory cell infiltration , and markers of proteolysis in skeletal muscle would come about as a result of repeated eccentric exercise and that gender may affect this adaptive response . Untrained male ( n = 8) and female ( n = 8) subjects performed two bouts ( bout 1 and bout 2 ) , separated by 5.5 wk , of 36 repetitions of unilateral , eccentric leg press and 100 repetitions of unilateral , eccentric knee extension exercises ( at 120 % of their concentric single repetition maximum ) , the subjects ' contralateral nonexercised leg served as a control ( rest ) . Biopsies were taken from the vastus lateralis from each leg 24 h postexercise . After bout 2 , the postexercise force deficit and the rise in serum creatine kinase ( CK ) activity were attenuated . Women had lower serum CK activity compared with men at all times ( P < 0.05 ) , but there were no gender differences in the relative magnitude of the force deficit . Muscle Z-disk streaming , quantified by using light microscopy , was elevated vs. rest only after bout 1 ( P < 0.05 ) , with no gender difference . Muscle neutrophil counts were significantly greater in women 24 h after bout 2 vs. rest and bout 1 ( P < 0.05 ) but were unchanged in men . Muscle macrophages were elevated in men and women after bout 1 and bout 2 ( P < 0.05 ) . Muscle protein content of the regulatory calpain subunit remained unchanged whereas ubiquitin-conjugated protein content was increased after both bouts ( P < 0.05 ) , with a greater increase after bout 2 . We conclude that adaptations to eccentric exercise are associated with attenuated serum CK activity and , potentially , an increase in the activity of the ubiquitin proteosome proteolytic pathway This study examined whether performing repeated bouts of eccentric exercise 2 and 4 days after an initial damaging bout would exacerbate muscle damage . One arm performed 3 sets of 10 eccentric actions of the elbow flexors ( ECC1 ) using a dumbbell set at 50 % of the maximal isometric force at 90 ° ( SINGLE ) . Two weeks later the same exercise was performed by the opposite arm with the exception that subsequent bouts were performed 2 ( ECC2 ) and 4 ( ECC3 ) days after ECC1 ( REPEATED ) . In the REPEATED condition , maximal isometric force ( MIF ) decreased to the same level immediately after ECC1–3 , and the decreases in range of motion ( ROM ) and increases in upper arm circumference immediately postexercise were similar among the bouts . However , no significant differences in changes in MIF , ROM , muscle soreness , and plasma creatine kinase activity were evident between the SINGLE and REPEATED conditions when excluding the changes immediately after ECC2 and ECC3 . These results suggest that ECC2 and ECC3  did not exacerbate muscle damage or affect the recovery process PURPOSE This study aim ed to evaluate the benefit of using low-intensity running or electromyostimulation ( EMS ) to hasten the recovery process from eccentric-contraction-induced injury . METHODS Before and 30 min , 24 h , 48 h , and 96 h after a one-legged downhill run , electrical stimulations were applied to the femoral nerve of healthy volunteers . Superimposed twitches were delivered during isometric maximal voluntary contraction ( MVC ) to determine the voluntary activation level ( % VA ) . For 4 d after the exercise , each subject performed either ( i ) 30 min of running at 50 % VO2max , ( ii ) 30 min of low-frequency EMS on the lower limb extensor muscles , or ( iii ) passive recovery . RESULTS Recovery time courses of the different variables did not differ significantly among the three experimental conditions . MVC decreased 30 min after the exercise and did not recover thereafter ( P < 0.001 ) . Percent VA was depressed after the exercise ( P < 0.05 ) but did not contribute to MVC decrement thereafter . Mechanical responses to 80- and 20-Hz stimulation ( P80 and P20 , respectively ) were significantly reduced over time ( P < 0.01 and P < 0.001 , respectively ) . Interestingly , MVC , P20 , and P80 decrements were not statistically different ( -9.6 + /- 14.5 % , -13.2 + /- 14.2 % , and -12.3 + /- 11.3 % , respectively ) at 48 h , and the P20.P80(-1 ) ratio showed complete recovery at this time . CONCLUSIONS The different recovery modes had no significant effect on the recovery time course of contractile properties . The prolonged torque loss is mainly due to peripheral alterations . Our results suggest that an alteration of the excitation-contraction coupling might be involved during the first 2 d after the eccentric exercise . From 2 to 4 d , damage to force-generating structures could account for the remaining torque deficit This investigation determined whether inflammatory mediators 1 ) have diurnal variations , 2 ) respond to high-force eccentric exercise , and 3 ) associate with markers of muscle damage after high-force eccentric exercise .  College-aged men and women ( n = 51 ) completed exercise ( 3 x 15 maximal eccentric elbow flexor actions using 1 arm ) and control conditions in r and om order . Blood was collected preexercise and 4 , 8 , 12 , 24 , 48 , and 96 h postexercise . Additional measures included maximal isometric force and midbiceps arm circumference ( to detect swelling ) . Serum and plasma were analyzed for soluble tumor necrosis factor receptor-1 ( sTNFR1 ) , IL-6 , C-reactive protein , cortisol , and creatine kinase ( CK ) activity . Relative to the 7:00 AM point in the control condition , diurnal decreases were measured at 12:00 PM and 4:00 PM for IL-6 and at 12:00 PM , 4:00 PM , and 8:00 PM for sTNFR1 and cortisol . sTNFR1 , IL-6 , CK , swelling , and soreness were higher in the exercise compared with the control condition . The largest of the inflammatory mediator responses was measured for IL-6 8 h postexercise in the exercise ( 3.00 + /- 3.59 pg/ml ) relative to the control condition ( 1.15 + /- 0.99 pg/ml ) . The IL-6 response ( time-matched exercise -- control concentration ) at 8 h associated ( r > 0.282 ) with muscle soreness at 24 and 96 h , and the cortisol response at 8 h associated ( r > 0.285 ) with swelling at 8 , 24 , and 96 h. Thus soreness and swelling , but not CK and strength loss , had a low association with the inflammatory response following eccentric exercise This study compared the magnitude of muscle damage induced when consecutive drop jumps ( DJs ) were performed on s and vs. firm ( wood ) surfaces from a height of 0.6 m. Eight subjects performed DJs on a s and surface at a depth of 0.2 m ( S condition ) , and 8 other subjects performed DJs on a wood surface ( F condition ) . Each set consisted of 20 DJs with an interval of 10 seconds between jumps . Subjects performed 5 sets of DJs with 2 minutes between sets . Maximal isometric force , muscle soreness , and plasma cre-atine kinase ( CK ) activity were measured immediately before and immediately after the DJ exercise as well as 1 , 24 , 48 , 72 , and 96 hours after the DJ exercise . All measures changed significantly ( p < 0.05 ) after exercise for both conditions ; however , significantly ( p < 0.05 ) smaller changes in these measures were evident for the S condition than for the F condition . These results show that DJs on a s and surface induce less muscle damage than on a firm surface . Training on s and may improve aerobic capacity or strength with a low risk of muscle damage The influence of different work-to-rest ( W : R ) ratios during fatigue induced by maximal eccentric contractions is unknown . The present study sought to exp and the underst and ing of the task-dependent nature of eccentric contractions , and the associated fatigue , during exercise and acute as well as extended recovery periods . Using a Biodex multi-joint dynamometer , the ankle dorsiflexors of eight men [ 26 ( 4 ) years ] were fatigued with 150 maximal eccentric contractions . Set structure was manipulated such that one leg performed 3 sets of 50 repetitions ( short rest protocol , SRP ) , and the other leg performed 15 sets of 10 repetitions ( long rest protocol , LRP ) . A 1-min rest interval separated each set , which result ed in 2 and 14 min of total rest for the SRP and the LRP , respectively . At fatigue , the SRP demonstrated a marginally greater loss of average peak eccentric torque than the LRP ( P<0.05 ) . In the acute period following fatigue , isometric peak torque loss and the degree of low-frequency fatigue ( LFF ) were not recovered ( P<0.05 ) and were equivalent for both protocol s. Significant impairment of both eccentric and isometric torque was persistent and equal for each protocol at 96 h of recovery ( P<0.05 ) . These findings suggest that the W : R ratio has a modest influence on the fatigue ( torque loss ) induced by maximal eccentric contractions , but maximal isometric torque during recovery and LFF are insensitive to changes in total rest time The objective of the present study was to investigate the impact of muscle length during stretch-shortening cycles on static and dynamic muscle performance . Animals were r and omly assigned to an  isometric ( control , Con , n = 12 ) , a  short-muscle-length ( S-Inj , 1.22 - 2.09 rad , n = 12 ) , or a long-muscle-length ( L-Inj , 1.57 - 2.44 rad , n = 12 ) group . The dorsiflexor muscles were exposed in vivo to 7 sets of 10 stretch-shortening contractions ( conducted at 8.72 rad/s ) or 7 sets of isometric contractions of the same stimulation duration by using a custom- design ed dynamometer . Performance was characterized by multipositional isometric exertions and positive , negative , and net work before exposure , 6 h after exposure , and 48 h after exposure to contractions . Real-time muscle performance during the stretch-shortening cycles was characterized by stretch-shortening parameters and negative , positive , and net work . The S-Inj group recovery ( force difference ) was similar to the Con group force difference at 48 h , whereas the L-Inj group force difference was statistically greater at 1.39 , 1.57 , and 1.74 rad than the Con group force difference ( P < 0.05 ) . Negative work ( P < 0.05 ) and net work ( P < 0.05 ) were statistically lower in the S-Inj and L-Inj groups than in the Con group 48 h after exposure to contractions . Of the real-time parameters , there was a difference in cyclic force with treatment during the stretch-shortening cycles ( P < 0.0001 ) , with the L-Inj group being the most affected . Thus longer ranges of motion result in a more profound isometric force decrement 48 h after exposure to contractions and in real-time changes in eccentric forces CONTEXT Numerous recovery strategies have been used in an attempt to minimize the symptoms of  delayed-onset muscle soreness ( DOMS ) .  Whole-body vibration ( WBV ) has been suggested as a viable warm-up for athletes . However , scientific evidence to support the protective effects of WBV training ( WBVT ) on muscle damage is lacking . OBJECTIVE To investigate the acute effect of WBVT applied before eccentric exercise in the prevention of DOMS . DESIGN R and omized controlled trial . SETTING University laboratory . PATIENTS OR OTHER PARTICIPANTS A total of 32 healthy , untrained volunteers were r and omly assigned to either the WBVT ( n = 15 ) or control ( n = 17 ) group . INTERVENTION(S ) Volunteers performed 6 sets of 10 maximal isokinetic ( 60 ° /s ) eccentric contractions of the dominant-limb knee extensors on a dynamometer . In the WBVT group , the training was applied using a vibratory platform ( 35 Hz , 5 mm peak to peak ) with 100 ° of knee flexion for 60 seconds before eccentric exercise . No vibration was applied in the control group . MAIN OUTCOME MEASURE(S ) Muscle soreness , thigh circumference , and pressure pain threshold were recorded at baseline and at 1 , 2 , 3 , 4 , 7 , and 14 days postexercise . Maximal voluntary isometric and isokinetic knee extensor strength were assessed at baseline , immediately after exercise , and at 1 , 2 , 7 , and 14 days postexercise . Serum creatine kinase was measured at baseline and at 1 , 2 , and 7 days postexercise . RESULTS The WBVT group showed a reduction in DOMS symptoms in the form of less maximal isometric and isokinetic voluntary strength loss , lower creatine kinase levels , and less pressure pain threshold and muscle soreness ( P < .05 ) compared with the control group . However , no effect on thigh circumference was evident ( P < .05 ) . CONCLUSIONS Administered before eccentric exercise , WBVT may reduce DOMS via muscle function improvement . Further investigation should be undertaken to ascertain the effectiveness of WBVT in attenuating DOMS in athletes PURPOSE It is known that submaximal eccentric exercise does not confer as strong a protective effect as maximal eccentric exercise . This study tested the hypothesis that four bouts of submaximal eccentric exercise would confer a similar protective effect to one bout maximal eccentric exercise . METHODS Thirty untrained men were placed into 4 x 40 % ( 40 % ) or control ( CON ) groups ( n = 15 per group ) by matching preexercise maximal voluntary isometric contraction strength ( MVC ) . The 40 % group performed 30 eccentric contractions with a load of 40 % MVC ( 40 % ECC ) every 2 wk for four times followed 2 wk later by 30 maximal eccentric exercise ( 100 % ECC ) of the elbow flexors of the nondominant arm . The CON group performed two bouts of the 100 % ECC separated by 2 wk . MVC at six angles , optimum angle ( OA ) , concentric isokinetic strength ( 30 degrees x s(-1 ) and 300 degrees x s(-1 ) ) , range of motion , upper arm circumference , plasma creatine kinase activity and myoglobin concentration , muscle soreness , and echo intensity of B-mode ultrasound images were taken before to 5 d after each exercise . RESULTS No significant differences in the changes in any measures were evident between the 100 % ECC of the 40 % group and the second 100 % ECC of the CON group . Changes in all measures except for OA and upper arm circumference after the second to the fourth 40 % ECC bouts were significantly smaller than those after the first 40 % ECC bout . The changes in the measures after any of the 40 % ECC bouts were significantly ( P < 0.05 ) smaller than those after the first 100 % ECC bout of the CON group . CONCLUSIONS These results suggest that repeating submaximal eccentric exercise confers the same magnitude of protective effect as one bout of maximal eccentric exercise against the subsequent maximal eccentric exercise 1 . The effects of maximum voluntary eccentric muscle actions on forearm flexor strength were studied at three different elbow joint angles ( 0.87 , 1.57 and 2.79 rad ) to examine whether subsequent impairment of contractile function is muscle length-specific . 2 . A bout of 70 maximum voluntary eccentric muscle actions performed with the forearm flexors elicited delayed muscle soreness , efflux of creatine kinase into the blood , loss of elbow joint range of motion and a prolonged decline in maximum voluntary isometric contraction torque at the three elbow angles monitored ( P < 0.01 ) in 30 subjects . 3 . The relative decline in maximum voluntary isometric contraction torque after eccentric exercise differed between elbow angles ( P < 0.01 ) . The greatest decline in strength relative to baseline was observed at the most acute elbow angle of 0.87 rad , followed by 1.57 and 2.79 rad respectively . Superimposed electrical stimulation in a subgroup of eight subjects did not increase the torque elicited by the forearm flexors during maximum voluntary contraction tests at the most acute elbow angle ( 0.87 rad ) at any time-point after eccentric exercise , suggesting the disproportionate loss of strength at short muscle length was not due to the inhibitory effects of muscle soreness . 4 . Measures of arm circumference and ability to fully flex the elbow ( in the same subgroup of eight subjects ) suggested the greater decline in strength at the acute elbow angle was not due to the possible confounding influences of muscle swelling and /or impaired muscle shortening ability on strength measurements at short muscle length . 5 . These data suggest a shift in the forearm flexor length-tension relationship could account for the disparate decline in strength between elbow angles after eccentric exercise . The disproportionate loss of strength at short muscle length suggests that eccentric exercise evoked a subtle increase in muscle length , perhaps attributable to the cumulative effects of regions of lengthened sarcomeres and /or series elastic elements The purpose of this study was to investigate the effects of high-force eccentric muscle contractions on collagen remodeling and on circulating levels of matrix metalloproteinases ( MMP ) and tissue inhibitors of metalloproteinases ( TIMP ) in humans . Nine volunteers [ 5 men and 4 women , mean age 23 ( SD 4 ) yr ] each performed a bout of  100 maximum voluntary eccentric contractions of the knee extensors . Muscle biopsies were taken before exercise and on days 4 and 22 afterward . Image analysis of stained tissue sections was used to quantify endomysial collagen staining intensity . Maximum voluntary contractile isometric force was recorded preexercise and on days 1 , 2 , 3 , 4 , 8 , 11 , and 14 postexercise . Venipuncture blood sample s were also drawn on these days for measurement of serum creatine kinase activity and concentrations of MMP-9 , TIMP-1 , TIMP-2 , and the MMP-2/TIMP-2 complex . Maximum voluntary contractile force declined by 39 + /- 23 % ( mean + /- SD ) on day 2 postexercise and recovered thereafter . Serum creatine kinase activity peaked on day 4 postexercise ( P < 0.01 ) . Collagen type IV staining intensity increased significantly on day 22 postexercise to 126 + /- 29 % ( mean + /- SD ) of preexercise values ( P < 0.05 ) . Serum MMP-9 levels increased on day 8 postexercise ( P < 0.01 ) , and serum TIMP-1 was also significantly elevated on days 1 , 2 , 3 , 4 , and 14 postexercise ( P < 0.05 ) . These results suggest that a single bout of eccentric muscle contractions results in remodeling of endomysial type IV collagen , possibly via the MMP pathway BACKGROUND Submaximal eccentric exertions occur occupationally when rapidly rising tool-generated forces exceed the operator 's capacity to react against them . The purpose of this study was to investigate the effects of short duration repetitive submaximal eccentric forearm exertions at levels comparable to industrial power h and tool use on dynamic mechanical properties ( stiffness , effective mass and damping ) and on forearm edema . METHODS This study investigated changes following short term repetitive submaximal eccentric exertions comparable to occupational levels . Eight male participants  exercised eccentrically for 30 min at 50 % of isometric maximum voluntary contraction forearm supination in a posture and loading similar to power h and tool use in the workplace . Dynamic mechanical properties ( stiffness , effective mass and damping ) of the upper limb were measured before , immediately following , and daily for three days after the activity . An MRI scan to assess edema was also performed for five of the participants before , on day one and day three following the activity . FINDINGS Mechanical stiffness decreased 51 % ( P < 0.05 ) and effective mass decreased 43 % ( P = 0.052 ) immediately following eccentric exercise .  Average isometric strength also decreased 42 % immediately following exercise ( P < 0.01 ) and pain persisted for two days . The recovery of static strength however was not correlated with changes in mechanical stiffness ( r = 0.56 ) or effective mass ( r = 0.30 ) . The exercised arms had a 360 % increase ( P < 0.01 ) in supinator-extensor T(2 ) relaxation time difference , a quantifiable measure of edema , one day after exercise while the non-exercised arms had no significant changes . INTERPRETATION Changes in both T(2 ) relaxation time , indicative of edema , and forearm mechanical properties , were observed following short duration submaximal repetitive exercise . If similar changes in dynamic mechanical properties of the upper extremity occur following repetitive submaximal eccentric activity in the workplace , they could negatively impact the ability of the arm to react to rapid forceful loading during repetitive industrial work activities and increase mechanical loading of the upper limb We examined whether a prior bout of eccentric exercise in the elbow flexors provided protection against exercise-induced muscle damage in the contralateral arm . Fifteen males ( age 22.7 ± 2.1 years ; height 178.6 ± 6.8 cm , mass 75.8 ± 9.3 kg ) were r and omly assigned to two groups who performed two bouts of 60 eccentric contractions ( 30 ° /s ) separated by 2 weeks : ipsilateral ( n = 7 , both bouts performed in the same arm ) , contralateral ( n = 8 , one bout performed in each arm ) . Strength , muscle soreness and resting arm angle ( RAA ) were measured at baseline and at 1 , 24 and 48 h post exercise . Surface electromyography was recorded during both bouts of exercise . The degree of strength loss was attenuated ( p < 0.05 ) in the ipsilateral group after the second bout of eccentric exercise ( −22 cf . −3 % for bout 1 and 2 at 24 h , respectively ) . Strength loss following eccentric exercise was also attenuated ( p < 0.05 ) at 24 h in the contralateral group ( −30 cf . 13 % for bout 1 and 2 , respectively ) . Muscle soreness ( ≈34 cf 19 mm ) and change in RAA ( ≈5 cf . 3 % ) were also lower following the second bout of eccentric exercise ( p < 0.05 ) , although there was no difference in the overall change in these values between groups . Median frequency ( MF ) was decreased by 31 % between bouts , with no difference between groups . Data support observations that the repeated bout effect transfers to the opposite ( untrained ) limb . The similar reduction in MF between bouts for the two groups provides evidence for a central ly mediated , neural adaptation The purpose of this investigation was to , firstly , examine the effects of repeated applications of ice massage on the indirect markers associated with muscle damage using a within-subjects cross-over design and secondly , to examine how ice massage affects muscle function in both static and dynamic contractions following unaccustomed eccentric exercise . Twelve males performed damaging exercise on two separate occasions . The protocol consisted of three sets of 10 maximal eccentric repetitions of the elbow flexors using isokinetic dynamometry . Subjects were r and omly assigned to an ice massage group or placebo group and received treatments immediately post-exercise , 24 and 48 h post-exercise . Muscle function ( maximal isometric , slow and fast isokinetic contractions ) , creatine kinase , myoglobin , muscle soreness , limb girth and range of motion were measured pre , immediately post , 24 , 48 , 72 and 96 h post-exercise . Significant time effects were observed for all dependent variables ( P<0.05 ) . There were no significant differences between treatments . Ice massage is ineffective in reducing the indirect markers associated with exercise-induced muscle damage and enhancing recovery of muscle function in male exercisers unaccustomed to eccentric biased exercise OBJECTIVE : We tested the hypothesis that altering the pre-exercise muscle temperature would influence the magnitude of muscle damage induced by eccentric exercise . SUBJECTS : Female students who had no experience in resistance training were placed into either a  microwave treatment group ( n = 10 ) or an icing treatment group ( n = 10 ) . DESIGN AND SETTING : Subjects in each group performed 12 maximal eccentric actions of the forearm flexors of each arm on 2 separate occasions separated by 4 weeks . Before testing , the exercise arm was subjected to either passive warming ( microwave ) or control for the microwave treatment group or cooling ( icing ) or control for the icing treatment group . The control arm performed the same exercise protocol without treatment . Limbs were r and omized for treatment or control and order of testing . Deep muscle temperature increased by approximately 3 degrees C after the microwave treatment and decreased approximately 5 degrees C after the icing treatment . MEASUREMENTS : We evaluated changes in maximal isometric force and indirect markers of muscle damage , including range of motion , upper arm circumference , muscle soreness , and plasma creatine kinase activity , in the microwave and control and icing and control groups using a 2-way , repeated- measures analysis of variance . RESULTS : All measures changed significantly ( P < .01 ) after exercise , but neither of the treatments demonstrated significant effects on most of the variables compared with the control . CONCLUSIONS : These results suggest that pre-exercise cooling does not affect the magnitude of muscle damage in response to eccentric exercise . Similarly , pre-exercise passive muscle warming did not prove beneficial in attenuating indicators of muscle damage . Thus , any beneficial effects of warm-up exercise can not be attributed to the effects of increased muscle temperature Abstract The purpose of this study was to investigate changes in muscle hardness after  eccentric exercise of the elbow flexors muscles that produce muscle shortening and swelling . To assess muscle hardness , a pressure method was used in which the force required to deform the tissue ( skin , subcutaneous tissue , muscle ) was recorded . Eleven healthy male students performed 24 maximal eccentric actions of the elbow flexor muscles with their non-dominant arms . Muscle hardness , maximal isometric force ( MIF ) , muscle soreness , plasma creatine kinase ( CK ) activity , relaxed elbow joint angle ( RANG ) , upper-arm circumference ( CIR ) and B-mode ultrasound transverse images were measured before , immediately after , and 1–5 days after exercise . A long-lasting decrease in MIF , muscle swelling shown by increases in CIR and muscle thickness , large increases in plasma CK activity , and development of muscle soreness indicated that damage occurred to the elbow flexor muscles . The RANG had decreased by approximately 20 ° at 1–3 days after exercise and showed a gradual recovery thereafter . The CIR increased gradually after exercise and peaked on day 5 post-exercise , the mean amount of increase in CIR being 18 mm . Muscle hardness measured at the relaxed elbow position did not change until 3 days after exercise , but increased significantly ( P < 0.01 ) on days 4 and 5 post-exercise . On the other h and , muscle hardness measured when forcibly extending the shortened elbow joint increased significantly ( P < 0.01 ) with time and peaked at 3 days after exercise . Muscle hardness assessed by the pressure method seems to reflect changes in muscle stiffness and swelling PURPOSE This study aim ed to determine the effects of 4 wk of antioxidants ( AOX ) supplementation on exercise-induced lipid peroxidation , muscle damage , and inflammation in kayakers . METHODS Subjects ( n = 20 ) were r and omly assigned to receive a placebo ( PLA ) or an AOX capsule ( AOX ; 272 mg of alpha-tocopherol , 400 mg of vitamin C , 30 mg of beta-carotene , 2 mg of lutein , 400 mug of selenium , 30 mg of zinc , and 600 mg of magnesium ) . Blood sample s were collected at rest and 15 min after a 1000-m kayak race , both before and after the supplementation period , for analysis of alpha-tocopherol , alpha-carotene , beta-carotene , lycopene , lutein plus zeaxanthin , vitamin C , uric acid , total AOX status ( TAS ) , thiobarbituric reactive acid substances ( TBARS ) and interleukin-6 ( IL-6 ) levels , and creatine kinase ( CK ) , superoxide dismutase ( SOD ) , glutathione reductase ( Gr ) , and glutathione peroxidase ( GPx ) activities . RESULTS With supplementation , plasma alpha-tocopherol ( P = 0.003 ) and beta-carotene ( P = 0.007 ) augmented significantly in the AOX group . IL-6 ( exercise , P = 0.039 ) , TBARS ( exercise , P < 0.001 ) , and uric acid ( exercise , P = 0.032 ) increased significantly in response to the exercise regardless of treatment group . Cortisol level raised more from pre- to postsupplementation period in the PLA group ( time x supplementation , P = 0.002 ) . Although TAS declined after exercise before intervention , it increased above preexercise values after the 4-wk period in the AOX group ( supplementation x time x exercise , P = 0.034 ) . CK increased after exercise in both groups ( exercise effect , P < 0.001 ) and decreased from week 0 to week 4 more markedly in the PLA group ( supplementation x time , P = 0.049 ) . CONCLUSIONS AOX supplementation does not offer protection against exercise-induced lipid peroxidation and inflammation and may hinder the recovery of muscle damage Repeated bouts of eccentric muscle contractions were used to examine indirect indices of exercise-induced muscle damage and adaptation in human skeletal muscle . Twenty-four subjects ( 18 females , 6 males ) aged 20.0 + /- 1.4 years ( mean + /- S.D. ) performed an initial bout of either 10 ( n = 7 ) , 30 ( n = 9 ) or 50 ( n = 8) maximum voluntary eccentric contractions of the knee extensors , followed by a second bout of 50 contractions 3 weeks later using the same leg . Muscle soreness was elevated after all bouts ( P < 0.05 , Wilcoxon test ) , although the initial bout reduced the soreness associated with the second bout . Force loss and a decline in the 20:100 Hz percutaneous electrical myostimulation force ratio were observed after all exercise bouts ( P < 0.01 ) . Serum creatine kinase activity was elevated following the initial bouts of 30 and 50 repetitions ( P < 0.01 ) , but there was no increase following 10 repetitions . No increase in serum creatine kinase activity was observed in any group following the second bout of contractions ( P > 0.05 ) . We conclude that skeletal muscle adaptation can be brought about by a single bout of relatively few eccentric muscle contractions . Increasing the number of eccentric muscle repetitions did not result in an increased prophylactic effect on skeletal muscle We examined whether polyphenols from dietary apple have protective effects against exercise-induced muscle strain injury . Sixteen male Wistar rats were r and omly assigned into the apple polyphenol ( APP ; N=8 ) and control ( CON ; N=8 ) groups . The APP and the CON groups were fed diets with and without 5 % APP , respectively . After a 3-wk feeding period , the gastrocnemii of the animals were subject to lengthening contractions with electrical stimulation and forced ankle dorsiflexion . Isometric torques were measured before and after the lengthening contractions and on days 1 , 2 , 3 , 5 , and 7 after the contractions . On day 7 , the animals were sacrificed and the gastrocnemii harvested . Thiobarbituric-acid-reactive substances , protein carbonyl , and mRNA of antioxidative proteins in the muscles were quantified . The APP group had significantly lower torque deficits than the CON group on days 3 , 5 , and 7 after the eccentric contractions . The thiobarbituric-acid-reactive substances and protein carbonyl levels in the case of the APP group were significantly lower than those in the case of the CON group . The APP group had significantly higher glutathione-S-transferase alpha1 mRNA levels than the CON group . Therefore , we conclude that dietary APPs have protective effects against lengthening contraction-induced muscle injury In this study , we investigated the effects of knee extensor length during eccentric exercise on indices of muscle damage and adaptation .  Subjects ( n = 7 ) performed two bouts of 75 maximal voluntary eccentric muscle actions at a knee joint angular velocity of 1.57 rad s(-1 ) . One bout was performed at a short muscle length ( bout S ) with a knee joint range of motion of 2.79 to 1.40 radians ( 160 degrees to 80 degrees ) , and a second with the contralateral knee extensors at a long muscle length ( bout L ) with a range of motion of 2.01 to 0.7 radians ( 120 degrees to 40 degrees ) . The maximum voluntary contractile force ( MVC ) was measured before and 5 min after exercise , and again on days 3 , 5 , 7 , 10 and 12 , at knee angles of 160 degrees , 120 degrees and 80 degrees . Muscle soreness was measured before exercise and on each day after exercise . Serum creatine kinase activity was measured before exercise and on days 3 , 5 , 7 , 10 and 12 post-exercise . The MVC declined after each bout ( P < 0.01 ) , with a greater decline after bout L ( P < 0.05 ) . Muscle soreness was higher relative to bout S on days 1 , 2 , 3 , 5 and 6 ( P < 0.05 ) . Although serum creatine kinase activity was elevated after both exercise bouts ( P < 0.01 ) , there was no difference between bouts . Functional muscle damage markers and muscle soreness suggest greater damage after bout L. Post-exercise angle-specific force decrements suggest a transient increase in muscle length after bout L but not bout PURPOSE This study examined the effects of a 7-d repeated maximal isokinetic eccentric training period on the indicators of muscle damage and inflammatory response . METHODS Twenty-two college-age males were r and omly assigned to  eccentric training ( ET )  ( N = 12 ) and  control groups  ( CON ) ( N = 10 ) . The initial exercise was 30 repetitions of maximal voluntary isokinetic eccentric contraction ( ECC1 ) on nondominant elbow flexors with Cybex 6000 at 60 degrees.s-1 angular velocity . The ET group performed the same exercise for the following 6 consecutive days ( referred to as ECC2 to ECC7 ) after ECC1 .  Upper arm circumference ( CIR ) , range of motion ( ROM ) , and maximal isometric force ( MIF ) were measured before , immediately after , and every 24 h for 7 consecutive days after ECC1 . Plasma creatine kinase ( CK ) , lactate dehydrogenase ( LDH ) , glutamic oxaloacetate transaminase ( GOT ) , leukocyte counts , and serum interleukin-1beta and -6 ( IL-1beta , IL-6 ) levels were assessed before ; at 2 h ; and at 1 , 3 , 4 , 6 , and 7 d after ECC1 . Muscle soreness was measured before and for 7 consecutive days after ECC1 . RESULTS The ECC1 produced significant changes in most of the measures for both groups ( P < 0.05 ) , with the exception of leukocyte counts ( P > 0.05 ) . No indicators of increased damage ( P > 0.05 ) were found from ECC2 to ECC7 for the ET group . CONCLUSION Continuous intensive isokinetic eccentric training performed with damaged muscles did not exacerbate muscle damage and inflammation after ECC1 . In addition , a muscular " adaptation effect " may occur as early as 24 h after ECC1 , as shown by the ET group 's performance for 6 consecutive days after ECC1 Reactive oxygen species may contribute to exercise-induced skeletal muscle damage , and antioxidants may protect against such damage . This study examined the effectiveness of prophylactic supplementation with vitamins C and E on symptoms of muscle damage in a single blind , two-group study design . Twelve male volunteers were r and omly assigned to either treatment or control groups . The treatment group received 500 mg of vitamin C and 1,200 IU of alpha−tocopherol daily and the control group received glucose placebo for 37 days . After 30 days of treatment , volunteers performed 300 maximal eccentric contractions of the knee extensor muscles of one leg . Maximal voluntary isometric contraction force and electrically evoked force at a frequency of 20 Hz and 50 Hz were recorded before and after exercise , and on days 1 , 2 and 7 after exercise . Muscle soreness question naires were completed and muscle girth recorded at the same time points . Eccentric contractile torque and work during the bout declined significantly in both groups ( P<0.001 ) , but this decline was smaller in the vitamin-supplemented group ( P<0.05 ) . Maximal voluntary isometric contraction force and 20:50 Hz force ratio declined significantly after exercise in both groups ( P<0.01 ) , but the decline was smaller in the treatment group on days 1 and 2 post-exercise ( P<0.05 ) . Both groups experienced similar significant muscle soreness and swelling after exercise . These data suggest that prior supplementation with dietary antioxidants ameliorates muscle functional decrements subsequent to eccentric muscle contraction To determine whether intermittent exposures to hyperbaric oxygen enhance recovery from delayed-onset muscle soreness of the quadriceps , we conducted a r and omized , controlled , double-blinded , prospect i ve study using 66 untrained men between the ages of 18 and 35 years . After the induction of muscle soreness , these subjects were treated in a hyperbaric chamber over a 5-day period in two phases , with four groups ( control , hyperbaric oxygen treatment , delayed treatment , and sham treatment ) in the first phase ; and three groups ( 3 days of treatment , 5 days of treatment , and sham treatment ) in the second phase . The hyperbaric exposures involved 100 % oxygen for 1 hour per day at 2.0 atm . The sham treatments involved 21 % oxygen for 1 hour per day at 1.2 atm . We monitored recovery using a leg dynamometer to test eccentric torque of the nondominant quadriceps muscle before and immediately after exercise and at 48 and 96 hours after exercise . Pain was tested daily using visual analog pain scales . In phase 1 a significant difference in recovery of eccentric torque was noted in the treatment group compared with the other groups . In phase 2 , the recovery of eccentric torque for the 5-day treatment group was significantly greater than for the sham group from immediately after exercise to 96 hours after exercise . The pain data did not differ significantly in any comparison in either phase . The results suggest that treatment with hyperbaric oxygen may enhance recovery of eccentric torque of the quadriceps muscle from delayed-onset muscle soreness This study examined markers of muscle damage following a repeated bout of maximal isokinetic eccentric exercise performed prior to full recovery from a previous bout . Twenty non-resistance trained volunteers were r and omly assigned to a control ( CON , n=10 ) or experimental ( EXP , n=10 ) group . Both groups performed 36 maximal isokinetic eccentric contractions of the elbow flexors of the non-dominant arm ( ECC1 ) . The EXP group repeated the same eccentric exercise bout two days later ( ECC2 ) . Total work and peak eccentric torque were recorded during each set of ECC1 and ECC2 . Isometric torque , delayed onset muscle soreness ( DOMS ) , flexed elbow angle and plasma creatine kinase ( CK ) activity were measured prior to and immediately following ECC1 and ECC2 . at 24h intervals for 7 days following ECC1 and finally on day 11 . In both groups , all dependent variables changed significantly during the 2 days following ECC1 . A further acute post-exercise impairment in isometric torque ( 30 + /- 5 % ) and flexed elbow angle ( 20 + /- 4 % ) was observed following ECC2 ( p<0.05 ) , despite EXP subjects producing uniformly lower work and peak eccentric torque values during ECC2 ( p<0.05 ) . No other significant differences between the CON and EXP groups were observed throughout the study ( p>0.05 ) . These findings suggest that when maximal isokinetic eccentric exercise is repeated two days after experiencing of contraction-induced muscle damage , the recovery time course is not significantly altered This study investigated whether a fatiguing concentric exercise performed immediately before eccentric exercise would exacerbate eccentric exercise-induced muscle damage .  One arm of nine female subjects ( mean + /- s : 23.3 + /- 6.7 years ) performed 12 maximal eccentric actions of the elbow flexors ( ECC ) , and the other arm performed 100 repetitions of isokinetic concentric actions of the elbow flexors followed by the same eccentric exercise ( CON-ECC ) . The two exercise regimens ( ECC and CON-ECC ) were separated by 2 weeks and presented in a counterbalanced order . Changes in muscle soreness level , maximal isometric force generation , relaxed and flexed elbow joint angle , upper arm circumference and plasma creatine kinase activity were compared between the ECC and CON-ECC conditions . All measures changed significantly after both ECC and CON-ECC ; however , there were significant differences in the changes between the conditions . A lower level of soreness , a faster recovery of maximal isometric force generation , a smaller decrease in relaxed elbow joint angle and a smaller increase in upper arm circumference and creatine kinase activity were evident after the CON-ECC condition compared to the ECC condition . Thus , it would seem that muscle damage was attenuated by performance of previous concentric exercise . An additional experiment using a different group of subjects ( n = 5 ) showed that warm-up exercise before the eccentric exercise also attenuated eccentric exercise-induced muscle damage Previous research has demonstrated that prior exercise may reduce the magnitude of muscle soreness and impaired function ( i.e. , repeated bout effect [ RBE ] ) observed during subsequent eccentric exercise . Previous investigations have predominantly used research design s that include single-joint exercise performed by untrained individuals . It is unknown how resistance trained individuals respond to novel multi-joint eccentric actions of the upper body and whether prior exercise offers protection . Thirty-one resistance trained men ( 23.4 ± 3.5 y , 177.2 ± 5.1 cm , 86.4 ± 16.5 kg , mean ± SD ) were r and omly assigned to repeated bout ( [ RB ] N = 15 ) or single bout ( [ CON ] N = 16 ) conditions . Both groups performed 100 eccentric actions of the bench press ( [ ECC ] at 70 % concentric 1 repetition maximum ) to induce muscle injury . Bilateral maximal isometric force , dynamic exercise performance ( e.g. , bench press throws ) , and muscle soreness were measured before , immediately after , and at 24 and 48 hours post-ECC . Total work , percent fatigue , and rating of perceived exertion ( ECC ) data were collected during ECC . Those assigned to RB condition exhibited less fatigue ( 9.5 vs. 22.6 % ) and lower RPE ( 14.8 vs. 17.1 ) during ECC . A significant interaction ( p < 0.05 ) was found such that RB individuals experienced less soreness at 24 ( 6.5 vs. 4.9 ) and 48 ( 6.6 vs. 3.9 ) hours postexercise than the CON condition . No significant group differences ( p < 0.05 ) were found for any measured performance variable . Although soreness , fatigue , and RPE suggest a RBE , this was not found in regards to exercise performance . It appears that in trained men , performing a strenuous high-volume eccentric exercise bout 2 weeks prior to an identical future bout offers no additional amelioration of impaired exercise performance The effect of a combination of a warm-up , stretching exercises and massage on subjective scores for  delayed onset muscle soreness ( DOMS )  and objective functional and biochemical measures was studied . Fifty people , r and omly divided in a treatment and a control group , performed eccentric exercise with the forearm flexors for 30 min . The treatment group additionally performed a warm-up and underwent a stretching protocol before the eccentric exercise and massage afterwards .  Functional and biochemical measures were obtained before , and 1 , 24 , 48 , 72 and 96h after exercise . The median values at the five post-exercise time points differed significantly for DOMS measured when the arm was extended ( p = 0.043 ) . Significant main effects for treatment were found on the maximal force ( p = 0.026 ) , the flexion angle of the elbow ( p = 0.014 ) and the creatine kinase activity in blood ( p = 0.006 ) . No time-by-treatment interactions were found . DOMS on pressure , extension angle and myoglobin concentration in blood did not differ between the groups . This combination of a warm-up , stretching and massage reduces some negative effects of eccentric exercise , but the results are inconsistent , since some parameters were significantly affected by the treatment whereas others were not , despite the expected efficacy of a combination of treatments . The objective measures did not yield more unequivocal results than the subjective DOMS scores Unaccustomed exercise ( usually of an eccentric nature ) is often followed by delayed onset muscle soreness ( DOMS ) . Previous studies have found that prior eccentric activity produces a training effect which reduces DOMS and morphological changes . The aim of this study was to examine the effects of a prior bout of maximal isokinetic eccentric exercise on DOMS , strength loss and plasma creatine kinase ( CK ) changes following a downhill run . Ten male subjects with a mean ( + /- S.D. ) age of 22.5 + /- 2.8 years , body mass of 62.67 + /- 0.05 kg and height of 176 + /- 3 cm were allocated to either a treatment group or a control group . The treatment group performed 100 maximal eccentric activations of the knee extensors in the dominant leg at 0.52 rad s-1 . Two weeks later , the downhill run was performed on a motor-driven treadmill . This consisted of five bouts of 8 min at a gradient of -10 % at a speed corresponding to 80 % of the predicted maximal heart rate . The untrained group performed the downhill run as above but without the prior isokinetic session . Tenderness measurements , plasma CK activity and concentric and eccentric isokinetic peak torque measurements of the knee extensors at 0.52 and 2.83 rad s-1 were recorded prior to , immediately following and 2 , 4 and 7 days after each protocol . The isokinetic protocol caused an increase ( P < 0.01 ) in CK and tenderness and a decrease ( P < 0.05 ) in concentric and eccentric torque at both speeds in the treatment group . Following the downhill run , a reduction in peak torque ( P < 0.01 ) was observed in the eccentric and concentric modes at both isokinetic speeds in the control group . For the treatment group , the decrease in peak torque occurred only at the faster eccentric speed . With the exception of the faster eccentric speed , the decrement in peak torque was greater in the control group in all post-exercise isokinetic strength tests . There was less tenderness ( P < 0.01 ) in the trained knee extensor muscle group . Peak torque also returned to pre-downhill values earlier for the trained group . Although plasma CK activity increased in both groups after downhill running , it was much lower ( P < 0.01 ) in the trained group . The results suggest that a prior bout of isokinetic eccentric training reduces muscle damage , reduces the amount of strength loss and decreases the sensation of DOMS after downhill running Surface  electromyographic ( EMG ) signals were recorded from the hamstring muscles during six sets of  submaximal isokinetic ( 2.6 rad s -1 ) eccentric ( 11 men , 9 women )  or concentric ( 6 men , 4 women )  contractions . The EMG per unit torque increased during eccentric ( P < 0.01 ) but not during concentric exercise . Similarly , the median frequency increased during eccentric ( P < 0.01 ) but not during concentric exercise . The EMG per unit torque was lower for submaximal eccentric than maximum isometric contractions ( P < 0.001 ) , and lower for submaximal concentric than maximum isometric contractions ( P < 0.01 ) . The EMG per unit torque was lower for eccentric than concentric contractions ( P < 0.05 ) . The median frequency was higher for submaximal eccentric than maximum isometric contractions ( P < 0.001 ) ; it was similar , however , between submaximal concentric and maximum isometric contractions ( P = 0.07 ) . Eccentric exercise result ed in significant isometric strength loss ( P < 0.01 ) , pain ( P < 0.01 ) and muscle tenderness ( P < 0.05 ) . The greatest strength loss was seen 1 day after eccentric exercise , while the most severe pain and muscle tenderness occurred 2 days after eccentric exercise . A lower EMG per unit torque is consistent with the selective recruitment of a small number of motor units during eccentric exercise . A higher median frequency during eccentric contractions may be explained by selective recruitment of fast-twitch motor units . The present results are consistent with the theory that muscle damage results from excessive stress on a small number of active fibres during eccentric contractions To assess the contribution of central and peripheral factors to changes in maximum voluntary force  and its length dependence after eccentric muscle damage , voluntary and twitch torque were measured across a wide angular range , along with voluntary activation using twitch interpolation . Isometric torque from both maximum voluntary contractions ( MVCs ) and paired twitches to motor nerve stimulation were measured from 60 to 150 deg elbow flexion in 10 deg increments in eight subjects . Optimal angles were determined by curve fitting . Each subject then performed eccentric contractions until voluntary torque had decreased by approximately 40 % . Measurements were repeated at 2 h , 1 day and 8 days post-exercise to follow acute and longer-term changes . Before exercise , the optimal angle was in the mid-range ( 93+/-10 deg ; mean+/-s.d . ) for MVCs , and at a more extended elbow angle for the twitch ( 106+/-6 deg , P < 0.05 ) . Voluntary activation was generally high ( > 94 % ) but depended on elbow angle , with activation being approximately 4 % lower at the most flexed compared to the most extended angle . Two hours after exercise , MVCs decreased 40 % , while twitch torque declined 70 % . All subjects showed a shift in optimal angle to longer muscle lengths for MVCs ( 17+/-16 deg at 2 h , 14+/-7 deg at day 1 , P < 0.05 ) . This shift contributed minimally ( approximately 3 % ) to the reduction in torque at 90 deg , as the torque-angle relation was relatively flat around the optimum . The twitch showed a smaller shift ( approximately 4 deg ) to longer lengths which was not statistically significant . Voluntary activation was significantly impaired in the early stages after exercise ( 2 h and day 1 , P < 0.05 ) , particularly at short muscle lengths . By 8 days after exercise , the optimal angle had returned to pre-exercise values , but MVC , twitch torque and voluntary activation had not fully recovered . Eccentric exercise causes a short-term shift in the optimal angle for MVCs and produces a length-dependent impairment in voluntary activation . Therefore , it appears that both central and peripheral factors limit muscle performance following eccentric damage , with limits to voluntary drive being especially important at short lengths PURPOSE This study investigated whether hyperbaric oxygen therapy ( HBOT ) improves recovery after exercise-induced muscle injury . METHODS Healthy male subjects ( N = 24 ) were r and omly assigned to either a placebo group or a HBOT group . Subjects were tested for maximal isometric strength ( preexercise ) of their right elbow flexors . Each subject then completed a high-force eccentric workout of the elbow flexor muscle group to induce  delayed onset muscle soreness (  DOMS ) . On the seven successive days after this workout , the subjects were exposed to a hyperbaric environment of 2.5 ATA for 60 min , inspiring either a normoxic mixture ( P(I)O2 = 0.2 ATA ; placebo group ) or a hyperoxic gas mixture ( P(I)O2 = 2.5 ATA ; HBOT group ) . Before the eccentric workout and daily for the next 10 d , measurements were obtained regarding : maximal isometric muscle strength of the elbow flexor muscles , right upper arm circumferences , and rating of the perceived muscle soreness . RESULTS Isometric strength decreased significantly from preexercise levels of 25.1 + /- 3.8 kp to postexercise levels of 12.0 + /- 4.6 kp , for the HBOT group , and from 24.6 + /- 3.4 kp to 12.5 + /- 3.7 kp , respectively , for the placebo group . Over the 10-d recovery period , there was no difference in the rate of recovery of muscle strength between the two groups . Perceived soreness peaked at about 48 h after exercise with no difference between groups . Also , the exercise-induced increases in arm circumference were similar in the two groups . CONCLUSIONS These results indicate that HBOT is not an effective therapy for the treatment of DOMS Abstract This study investigated whether performing repeated bouts of maximal voluntary isokinetic eccentric exercise ( MAX1 ) on 3 ( MAX3 ) and 6 days ( MAX6 ) after the initial bout would produce significant changes in the indirect markers of muscle damage and total work . A secondary purpose was to determine whether participants ' psychological maximal effort was equivalent to the physiological maximal effort during muscle soreness . Male university students were assigned r and omly to a control group ( n = 12 ) and a group that repeated the exercise ( EX ; n = 12 ) . The MAX1 was 3 × 10 repetitions of the nondominant elbow flexors on the Cybex 6000 system at a speed of 60 deg/s . The EX group performed the same exercise 3 days and 6 days after MAX1 . The range of motion and maximal isometric force ( MIF ) , muscle soreness index , plasma creatine kinase , and glutamic-oxaloacetate transaminase activities were measured before and every 24 hr for 9 days after MAX1 for both groups . MIF was also assessed once before and immediately after each MAX for the EX group . There were no significant changes ( p > .05 ) between the groups for all criterion measures , except for total amount of work ( p < .05 ) . It is concluded that strenuous voluntary isokinetic eccentric exercise performed with damaged muscles does not appear to exacerbate damage or influence the recovery process . Although individuals could perform repeated MAXs , the total work performed was significantly reduced . This has practical implication s in strength training for coaches and athletes during muscle damage Jakeman , JR , Byrne , C , and Eston , RG . Efficacy of lower limb compression and combined treatment of manual massage and lower limb compression on symptoms of exercise-induced muscle damage in women . J Strength Cond Res 24(11 ) : 3157 - 3165 , 2010-Strategies to manage the symptoms of exercise-induced muscle damage ( EIMD ) are widespread , though are often based on anecdotal evidence . The aim of this study was to determine the efficacy of a combination of manual massage and compressive clothing and compressive clothing individually as recovery strategies after muscle damage . Thirty-two female volunteers completed 100 plyometric drop jumps and were r and omly assigned to a passive recovery ( n = 17 ) , combined treatment ( n = 7 ) , or compression treatment group ( n = 8) . Indices of muscle damage ( perceived soreness , creatine kinase activity , isokinetic muscle strength , squat jump , and countermovement jump performance ) were assessed immediately before and after 1 , 24 , 48 , 72 , and 96 hours of plyometric exercise . The compression treatment group wore compressive tights for 12 hours after damage and the combined treatment group received a 30-minute massage immediately after damaging exercise and wore compression stockings for the following 11.5 hours . Plyometric exercise had a significant effect on all indices of muscle damage ( p < 0.05 ) . The treatments significantly reduced decrements in isokinetic muscle strength , squat jump performance , and countermovement jump performance and reduced the level of perceived soreness in comparison with the passive recovery group ( p < 0.05 ) . The addition of sports massage to compression after muscle damage did not improve performance recovery , with recovery trends being similar in both treatment groups . The treatment combination of massage and compression significantly moderated perceived soreness at 48 and 72 hours after plyometric exercise ( p < 0.05 ) in comparison with the passive recovery or compression alone treatment . The results indicate that the use of lower limb compression and a combined treatment of manual massage with lower limb compression are effective recovery strategies following EIMD . Minimal performance differences between treatments were observed , although the combination treatment may be beneficial in controlling perceived soreness This study aim ed to investigate the efficacy of lower limb compression as a recovery strategy following exercise-induced muscle damage ( EIMD ) . Seventeen female volunteers completed 10 × 10 plyometric drop jumps from a 0.6-m box to induce muscle damage . Participants were r and omly allocated to a passive recovery ( n = 9 ) or a compression treatment ( n = 8) group . Treatment group volunteers wore full leg compression stockings for 12 h immediately following damaging exercise . Passive recovery group participants had no intervention . Indirect indices of muscle damage ( muscle soreness , creatine kinase activity , knee extensor concentric strength , and vertical jump performance ) were assessed prior to and 1 , 24 , 48 , 72 , and 96 h following plyometric exercise . Plyometric exercise had a significant effect ( p ≤ 0.05 ) on all indices of muscle damage . The compression treatment reduced decrements in countermovement jump performance ( passive recovery 88.1 ± 2.8 % vs. treatment 95.2 ± 2.9 % of pre-exercise ) , squat jump performance ( 82.3 ± 1.9 % vs. 94.5 ± 2 % ) , and knee extensor strength loss ( 81.6 ± 3 % vs. 93 ± 3.2 % ) , and reduced muscle soreness ( 4.0 ± 0.23 vs. 2.4 ± 0.24 ) , but had no significant effect on creatine kinase activity . The results indicate that compression clothing is an effective recovery strategy following exercise-induced muscle damage This study investigated if vitamin C supplementation before and after eccentric exercise could reduce  muscle soreness ( MS ) , oxidative stress , and muscle function .  Eighteen healthy men r and omly assigned to either a placebo ( P ) or vitamin C ( VC ) ( 3 g/d ) treatment group took pills for 2 wk prior and 4 d after performing 70 eccentric elbow extensions with their non-dominant arm . MS increased in both groups with significantly reduced MS for the first 24 h with VC . Range of motion was reduced equally in both groups after the exercise ( P > or = 0.05 ) . Muscle force declined equally and was unaffected by treatment . VC attenuated the creatine kinase ( CK ) increase at 48 h after exercise with similar CK after this time . Glutathione ratio ( oxidized glutathione/total glutathione ) was significantly increased at 4 and 24 h with P but VC prevented this change . These data suggest that vitamin C pretreatment can reduce MS , delay CK increase , and prevent blood glutathione oxidation with little influence on muscle function loss PURPOSE Many symptoms of eccentric muscle damage can be substantially reduced if a similar eccentric bout is repeated within several weeks of the initial bout . The purpose of this study was to determine whether a nondamaging , low repetition , low volume eccentric exercise bout could also provide a protective/adaptive effect . METHODS Subjects were assigned to a control ( CON ) , eccentric exercise ( ECC ) , or low volume familiarized eccentric exercise group ( LV+ECC ) . Before the study , the LV+ECC group performed six maximal eccentric contractions during two familiarization sessions . The main eccentric bout targeted the elbow flexor muscle group and consisted of 36 maximal eccentric contractions . Muscle soreness , upper arm girth , elbow angle , creatine kinase activity , isometric torque , and concentric and eccentric torque at 0.52 and 3.14 rad.s-1 were assessed 0 , 1 , 2 , 3 , 4 , 7 , and 10 d postexercise . RESULTS No evidence of muscle damage was observed as a result of the low volume eccentric bouts . Nevertheless , with the exception of muscle soreness and concentric torque , all variables recovered more rapidly in the LV+ECC group ( P < 0.05 ) . CONCLUSION Adaptation to eccentric exercise can occur in the absence of significant muscle damage . Exposure to a small number of nondamaging eccentric contractions can significantly improve recovery after a subsequent damaging eccentric bout . Furthermore , this adaptation appears to be mode-specific and not applicable to concentric contractions This study investigated the hypothesis that a light eccentric exercise ( ECC ) that does not induce a loss of muscle function and delayed onset muscle soreness would confer a protective effect against a more strenuous ECC . Eighteen young men were r and omly placed into two groups : 10 - 40 % ( n=9 ) and 40 % ( n=9 ) . Subjects in the 10 - 40 % group performed ECC of the elbow flexors ( six sets of five reps ) using a dumbbell set at 10 % of maximal isometric strength ( MVC ) at an elbow joint angle of 90 degrees , followed 2 days later by ECC using a dumbbell weight of 40 % MVC . Subjects in the 40 % group performed the 40 % ECC only . Changes in MVC , range of motion ( ROM ) , upper arm circumference ( CIR ) , plasma creatine kinase ( CK ) activity and muscle soreness before , immediately after , 1 - 5 and 7 days following the 40 % ECC were compared between groups by a two-way repeated measures ANOVA . No significant changes in any of the criterion measures were found immediately and 1 - 2 days after the 10 % ECC . Following the 40 % ECC , the 10 - 40 % group showed significantly ( P<0.05 ) smaller decreases in MVC and ROM , and smaller increases in muscle soreness compared with the 40 % group , but no significant differences between groups were evident for CIR and plasma CK activity . These results suggest that the 10 % ECC induced some protection against a subsequent bout of 40 % ECC performed 2 days later . It appears that the light eccentric exercise preconditioned the muscles for exposure to the subsequent damaging eccentric exercise bout The etiology of myofascial tenderness and pain of masticatory muscles in humans is difficult to underst and . Parafunctional oral habits such as tooth grinding or vigorous chewing are thought to be factors . The objective of this study was to determine if masticatory muscles are susceptible to weakness and injury induced by repetitive , dynamic , forced-lengthening contractions . Results would support the hypothesis that contraction-induced injuries could occur in hyperactive masticatory muscles of humans in response to parafunctional oral habits . Mice were anesthetized and r and omly assigned to three groups : non-treated controls , treated by repetitive passive jaw opening , or treated by repetitive isometric tetanic contractions with lengthening by jaw opening . In each treatment group , masticatory muscle injury was evaluated by contractile tension , plasma creatine kinase , and muscle glycogen . Contractile tension was determined at different stimulation frequencies and was significantly decreased 5 min , 4 h , and 72 h after repetitive contraction/lengthening . Plasma creatine kinase was significantly elevated at 4 but not at 72 h post-treatment in mice subjected to repetitive contraction/lengthening . Masticatory muscle glycogen was not significantly different in any groups at 4 or 72 h post-treatment . These results indicate that contraction injuries can be induced in masticatory muscle of mice by forced lengthening contractions which simulate eccentric contractions While various models for exercise-induced muscle damage ( EIMD ) have been introduced , many of them use maximal voluntary contractions of the elbow flexors and knee extensors performed on isokinetic dynamometers . Few studies have used exercise protocol s that attempt to replicate submaximal eccentric muscle actions that commonly occur during daily activities . Downhill backwards walking has been used previously as an EIMD model . However , the common markers of muscle damage have not been systematic ally examined for this model . The purpose of this study was to determine the magnitude of muscle damage induced by downhill backward walking with regard to changes in commonly-used indirect markers of EIMD . Twenty subjects aged between 19 y and 42 y completed a bout of 60 min of downhill ( -15 % ) backward walking in which a single limb performed submaximal eccentric actions at a stepping rate of 30 - 35 strides per min . A repeated measures ANOVA revealed significant ( p < 0.05 ) increases from baseline for soreness ( 24 hr- 96 hr ) , tenderness ( 24 hr - 96 hr ) , and plasma creatine kinase activity ( 0.5 hr - 96 hr ) , and significant decreases ( p < 0.05 ) in maximal voluntary isometric ( approximately 25 % ) and isokinetic ( -15 % ) strength ( 0.5 hr - 96 hr ) post-walk for the exercised limb . The time course of observed changes in these markers was similar to that reported for EIMD models of the elbow flexors and knee extensors . However , the magnitude of muscle damage appeared more consistent with that demonstrated following submaximal eccentric exercise This study investigated whether 10 drop jumps ( DJs ) would confer protective effect against muscle damage and soreness in a subsequent bout of 50 DJs . Sixteen men were r and omly placed into either a group performing 1 set of 10 DJs followed by 5 sets of 10 DJs ( 10–50 , n = 8) or another group performing 2 bouts of 5 sets of 10 DJs ( 50–50 , n = 8) separated by 2 weeks . The DJs were performed from a box height of 0.6 m , with a 10-second interval between jumps and a 1-minute rest between sets . Jump height , peak vertical ground reaction force , ground contact time , and heart rate during DJs were measured , and blood lactate concentration was assessed before and immediately after DJs . Changes in maximal isometric ( ISO ) and isokinetic concentric torque ( CON ) , vertical jump , muscle soreness , and plasma creatine kinase activity before , immediately after , and at 1 , 24 , 48 , and 72 hours following exercise were compared between groups for the first and second bouts and between the bouts by a 2-way repeated- measures analysis of variance . Changes in ISO , CON , vertical jump , and muscle soreness were significantly ( p < 0.05 ) smaller for 10 DJs compared with 50 DJs ; however , no signifi- ca nt differences in the measures between groups were evident following the second bout . The changes in the measures following 50 DJs in the 10–50 group were significantly ( p < 0.05 ) smaller than those following the first bout of the 50–50 group . These results suggest that 10 DJs and 50 DJs conferred the same magnitude of protective effect against muscle damage by 50 DJs Nine participants performed two bouts of a step exercise , during which the quadriceps muscle of one leg acted eccentrically . Before and after the exercise , isokinetic torque was measured over a range of knee angles to determine the optimum angle for torque . Immediately after the first bout of exercise , the quadriceps showed a significant ( P < 0.05 ) shift of 15.6 + /- 1.4 degrees ( mean + /-sx ) of its optimum angle in the direction of longer lengths , suggesting the presence of damage . A drop in peak torque , together with delayed soreness and swelling , confirmed that damage to muscle fibres had occurred . After the second bout of exercise , 8 days later , the shift in optimum angle was 10.4 + /- 1.0 degrees , which was significantly less than after the first bout ( P < 0.05 ) . Other indicators of damage were also reduced . In addition , the muscle exhibited a sustained shift in optimum angle ( 3.4 + /- 0.9 degrees ) , suggesting that some adaptation had taken place after the first bout of exercise . We conclude that muscles like the quadriceps can show evidence of damage after a specific programme of eccentric exercise , followed by an adaptation response . This is despite the fact that the quadriceps routinely undergoes eccentric contractions in everyday activities The purpose of this study was to examine the effectiveness of a single bout of cold-water immersion on recovery from exercise-induced muscle damage . Eighteen physically active female volunteers ( age 19.9 ( ±0.97 years ) , height 1.66 ( ±0.05 m ) , mass 63.7 ( ±10 kg ) , completed 10 sets of 10 counter-movement jumps to induce muscle damage and were r and omly allocated to a control or treatment group . The treatment group was given a single 10-min bout of lower limb cold-water immersion therapy at 10 ° C immediately following damage-inducing exercise . Indicators of muscle damage ( plasma creatine kinase activity , perceived soreness and maximal voluntary contraction of the quadriceps ) were assessed immediately prior to counter-movement jumps , and at 1 , 24 , 48 , 72 and 96 h , following the damaging exercise . Significant ( p = 0.05 ) time effects were recorded on all indicators of muscle damage , but there were no significant group or group × time interaction effects found on any of the measured variables . The results indicate that a single bout of cold-water immersion after a damaging bout of exercise has no beneficial effects on the recovery from exercise-induced muscle damage CONTEXT A dehydrated individual who performs eccentric exercise  may exacerbate skeletal muscle damage , leading to structural , contractile , and enzymatic protein denaturation , in addition to the myofiber and connective damage result ing from the eccentric muscle tension . OBJECTIVE To identify the effects of dehydration on 5 physiologic characteristics of  delayed-onset muscle soreness ( DOMS ) in normothermic men after an eccentric exercise perturbation . DESIGN R and omized group test-retest design . SETTING Laboratory . PATIENTS OR OTHER PARTICIPANTS Ten healthy male volunteers r and omly assigned to either a euhydration ( age = 26.2 + /- 4.9 years , height = 174.1 + /- 6.0 cm , mass = 86.5 + /- 15.3 kg ) or dehydration ( age = 25.8 + /- 2.2 years , height = 177.2 + /- 3.1 cm , mass = 84.4 + /- 3.8 kg ) group . INTERVENTION(S ) Subjects performed treadmill walking for 45 minutes in either a thermoneutral ( euhydration ) or a hot , humid ( dehydration ) environment . After a rest period to allow for return to the normothermic condition , DOMS was induced with a 45-minute downhill run . MAIN OUTCOME MEASURES We assessed 5 physiologic characteristics of DOMS before and at intervals after the eccentric exercise . The characteristics were perceived pain of the bilateral quadriceps and overall body , bilateral punctate tenderness of the superficial quadriceps muscles , bilateral knee-flexion passive range of motion , bilateral thigh circumference , and bilateral isometric quadriceps muscle strength . Thermoregulatory and cardiovascular measures were obtained to monitor participants ' heat load during exercise . RESULTS The experimental protocol produced a 0.9 % increase in body mass of the euhydration group and a significant 2.7 % decrease in body mass of the dehydration group . The downhill-running exercise perturbation induced DOMS in both the euhydrated and dehydrated participants , based on increased bilateral quadriceps and overall body perceived pain and punctate tenderness of the bilateral vastus medialis muscle . The signs and symptoms of DOMS after an eccentric exercise perturbation were not exacerbated by moderate dehydration of 2.7 % body mass after rest and return to the normothermic condition . CONCLUSIONS Significantly dehydrated participants who rested and returned to a normothermic condition did not experience increased characteristics of DOMS This study investigated whether the second eccentric exercise performed 3 days after the initial bout would exacerbate muscle damage and retard the recovery .  Fifty-one athletes performed  30 eccentric actions of the elbow flexors  using a dumbbell weighted 100 % of the maximal isometric force ( MIF ) at the elbow joint angle of 908 ( ECC1 ) . Three days after ECC1 , all subjects except those in the control group ( n = 12 ) performed the second bout ( ECC2 ) with the same ( 100 % ) intensity ( n = 12 ) , 90 % ( n = 13 ) , or 80 % ( n = 14 ) of the ECC1 . Some subjects , especially in the 100 % group , required spotting for ECC2 but made maximal effort to complete the exercise . MIF , range of motion , upper-arm circumference , muscle soreness , muscle proteins in the blood , and ultrasound images were used to assess muscle damage . Changes in these measures for 9 days following ECC1 were compared among groups by 2-way analysis of variance ( ANOVA ) with repeated measures . All criterion measures changed significantly after ECC1 ; however , no significant differences between the groups were evident for any of the changes in the measures . These results suggest that it is possible for athletes to complete the second bout if the intensity is reduced 10–20 % from the initial bout . No significant differences between the control group and other groups indicate that the second eccentric exercise performed 3 days after the initial bout does not exacerbate muscle damage and retard the recovery regardless of the intensity of the second bout . It is concluded that the elbow flexors can perform high-intensity eccentric exercise in the early stage of recovery from the initial bout and are not damaged further by performing a subsequent bout 3 days after the first The proteolytic enzyme , bromelain , reportedly has therapeutic effects in the treatment of inflammation and soft tissue injuries . We tested the hypothesis that bromelain attenuates skeletal muscle injury induced by lengthening contractions . The left extensor digitorum longus ( EDL ) muscle of anesthetized hamsters was injured using a motorized foot pedal which repeatedly flexed/extended the foot through a range of 125 degrees . The EDL muscle was electrically stimulated for 400 ms during plantarflexion . Animals were assigned r and omly to either a 0-d group ( evaluated 3-h post-injury ) or to untreated ( UT ) or bromelain-treated ( T ) groups , evaluated 3 , 7 , or 14 d post-injury . Following injury , T received 5 mg.kg-1 b.w . of bromelain , twice daily . Maximum isometric tetanic force ( Po ) was measured in vitro , then muscles were fixed , sectioned , and examined for evidence of fiber damage . The Po of injured muscles from T were higher than Po of injured muscles from UT at 3 ( 18.7 + /- 0.4 vs 16.5 + /- N.cm-2 and 14 d ( 20.5 + /- 0.6 vs 18.2 + /- 0.6 N.cm-2 ) ( P less than 0.05 ) , but not 7 d ( 19.5 + /-0.7 vs 17.7 + /- 0.8 N.cm-2 ) . The Po of UT injured muscles were significantly lower than Po of contralateral control muscles at all time periods . Po of injured muscles from T were lower than Po from control muscles at 3 and 7 d ( P less than 0.05 ) , but not 14 d. The number of intact fibers of 3-d UT injured muscles was lower than the number of intact fibers in control muscles ( P less than 0.05 ) . ( ABSTRACT TRUNCATED AT 250 WORDS PURPOSE The purpose of this study was to examine the role of branched-chain amino acid ( BCAA ) supplementation during recovery from intense eccentric exercise . METHODS Twenty-four non-weight-trained males were assigned to one of two groups : one group ( supplementary , SUP ) ingested BCAA beverages ( n = 12 ) ; the second group ( placebo , PLA ) ingested artificially flavored water ( n = 12 ) . Diet was controlled throughout the testing period to match habitual intake . The eccentric exercise protocol consisted of 12 x 10 repetitions of unilateral eccentric knee extension exercise at 120 % concentric one repetition maximum . On the day of the exercise , supplements were consumed 30 min before exercise , 1.5 h after exercise , between lunch and dinner , and before bed . On the following 2 d , four supplements were consumed between meals . Muscle soreness , muscle function , and putative blood markers of muscle damage were assessed before and after ( 1 , 8 , 24 , 48 , and 72 h ) exercise . RESULTS Muscle function decreased after the eccentric exercise ( P < 0.0001 ) , but the degree of force loss was unaffected by BCAA ingestion ( 51 % + /- 3 % with SUP vs -48 % + /- 7 % with PLA ) . A decrease in flexed muscle soreness was observed in SUP compared with PLA at 48 h ( 21 + /- 3 mm vs 32 + /- 3 mm , P = 0.02 ) and 72 h ( 17 + /- 3 mm vs 27 + /- 4 mm , P = 0.038 ) . Flexed muscle soreness , expressed as area under the curve , was lower in SUP than in PLA ( P = 0.024 ) . CONCLUSIONS BCAA supplementation may attenuate muscle soreness , but it does not ameliorate eccentric exercise-induced decrements in muscle function or increases in reputed blood markers of muscle damage , when consumed before exercise and for 3 d after an eccentric exercise bout Background The use of sports massage is very common in the athletic community . However , only a few studies have shown any therapeutic effect of massage . Hypothesis Sports massage can improve the recovery after eccentric exercise . Study Design Prospect i ve r and omized clinical trial . Methods Sixteen subjects performed 300 maximal eccentric contractions of the quadriceps muscle bilaterally .  Massage was given to 1 leg , whereas the other leg served as a control . Subjects were treated once daily for 3 days . Maximal strength was tested on a Kin-Com dynamometer , and functional tests were based on 1-leg long jumps . Pain was evaluated using a visual analog scale . Results There was a marked loss of strength and function of the quadriceps directly after exercise and on the third day after exercise . The massage treatment did not affect the level or duration of pain or the loss of strength or function following exercise . Conclusion Sports massage could not improve the recovery after eccentric exercise The aims of this study were to investigate the sarcomeric accumulation and expression of heat shock proteins ( HSPs ) after two bouts of maximal eccentric exercise .  Twenty-four subjects performed two bouts of 70 maximal voluntary eccentric actions using the elbow flexors in one arm . The bouts were separated by 3 wk . The changes in concentric ( 60 degrees/s ) and isometric ( 90 degrees ) force-generating capacity were monitored for 9 days after each bout , and biopsies were taken 1 and 48 h and 4 and 7 days after bout 1 and 1 and 48 h after bout 2 . The content of HSP27 , alphaB-crystallin , HSP70 , and desmin in the cytosolic and cytoskeleton/myofibrillar fractions of homogenized muscle sample s was determined by immunoassays , and the cellular and subcellular localization of the HSPs in the myofibrillar structure was analyzed by conventional and confocal immunofluorescence microscopy and quantitative electron microscopy . The force-generating capacity was reduced by approximately 50 % and did not recover completely during the 3 wk following bout 1 . After bout 2 , the subjects recovered within 4 days . The HSP levels increased in the cytosolic fraction after bout 1 , especially HSP70 ( approximately 300 % 2 - 7 days after exercise ) . Increased levels of HSP27 , alphaB-crystallin , and HSP70 were found in the cytoskeletal/myofibrillar fraction after both bouts , despite reduced damage after bout 2 . At the ultrastructural level , HSP27 and alphaB-crystallin accumulated in Z-disks , in intermediate desmin-like structures ( alphaB-crystallin ) , and in areas of myofibrillar disruption . In conclusion , HSP27 and alphaB-crystallin accumulated in myofibrillar structures , especially in the Z-disks and the intermediate structures ( desmin ) . The function of the small HSPs is possibly to stabilize and protect the myofibrillar structures during and after unaccustomed eccentric exercise . The large amount of HSP27 , alphaB-crystallin , and HSP70 in the cytoskeletal/myofibrillar fraction after a repeated bout of exercise suggests a protective role as part of the repeated-bout effect Thirty-two volunteers participated in a two-period crossover study in which ibuprofen was tested against an identical placebo for its effectiveness in reducing  muscle soreness and damage  after two bouts of downhill running .  Subjective soreness , quadriceps isometric strength and isometric endurance time at 50 percent of maximum strength , serum activities of creatine kinase , lactate dehydrogenase and aspartate transaminase and serum levels of creatinine and urea were recorded at intervals up to 72 hours after exercise . Each downhill run produced muscle soreness , and a decline in muscle strength and 50 percent endurance time , although these parameters were unaffected by ibuprofen treatment . All serum parameters measured increased after both runs , but for the three enzymes this increase was smaller after the second run . Serum creatine kinase and urea levels were higher in the ibuprofen group after both runs . These results indicate that ibuprofen is not an appropriate treatment for delayed onset muscle soreness and damage The purpose of this study was to examine the effects of ibuprofen on  delayed onset muscle soreness ( DOMS ) , indirect markers of muscle damage and muscular performance . Nineteen subjects ( their mean [ ± SD]age , height , and weight was 24.6 ± 3.9 years , 176.2 ± 11.1 cm , 77.3 ± 18.7 kg ) performed the eccentric leg curl exercise to induce muscle soreness in the hamstrings . Nine subjects took an ibuprofen pill of 400 mg every 8 hours within a period of 48 hours , whereas 10 subjects received a placebo r and omly ( double blind ) . White blood cells ( WBCs ) and creatine kinase ( CK ) were measured at pre-exercise , 4–6 , 24 , and 48 hours after exercise and maximal strength ( 1 repetition maximum ) . Vertical jump performance and knee flexion range of motion ( ROM ) were measured at pre-exercise , 24 and 48 hours after exercise . Muscle soreness increased ( p < 0.05 ) in both groups after 24 and 48 hours , although the ibuprofen group yielded a significantly lower value ( p < 0.05 ) after 24 hours . The WBC levels were significantly ( p < 0.05 ) increased 4–6 hours post-exercise in both groups with no significant difference ( p > 0.05 ) between the 2 groups . The CK values increased ( p < 0.05 ) in the placebo group at 24 and 48 hours postexercise , whereas no significant differences ( p > 0.05 ) were observed in the ibuprofen group . The CK values of the ibuprofen group were lower ( p < 0.05 ) after 48 hours compared with the placebo group . Maximal strength , vertical jump performance , and knee ROM decreased significantly ( p < 0.05 ) after exercise and at 24 and 48 hours postexercise in both the placebo and the ibuprofen groups with no differences being observed ( p > 0.05 ) between the 2 groups . The results of this study reveal that intake of ibuprofen can decrease muscle soreness induced after eccentric exercise but can not assist in restoring muscle function This study examined whether a second bout of maximal eccentric exercise performed 3 days after the first exercise bout would produce further changes in muscle damage and electromyographic activity ( EMG ) . Male students ( n=26 ) were r and omly assigned to experimental 70 ( EX70 ; n=9 ) , experimental 30 ( EX30 ; n=8 ) , and control ( CON ; n=9 ) groups . The initial exercise was 30 maximal voluntary isokinetic eccentric contractions ( MAX1 ) on non-dominant elbow flexors at 60 ° s−1 ( 1.05 rad s-1 ) . The EX70 and EX30 groups performed a second bout of 70 and 30 eccentric contractions ( MAX2 ) , respectively , 3 days after MAX1 . Upper arm circumference , range of motion , strength , integrated EMG ( IEMG ) , and mean power frequency ( MPF ) were measured before , immediately after , and once a day for 9 days after MAX1 . Plasma creatine kinase ( CK ) activity and muscle soreness were assessed before and for 9 days after MAX1 . Total work , work per contraction , IEMG , and MPF were also recorded during MAX1 and MAX2 . All indicators of muscle damage changed following MAX1 for each group ( P<0.05 ) , but no indicators of additional damage ( P>0.05 ) were apparent after MAX2 for either the EX70 or EX30 groups . IEMG ( P=0.03 ) and MPF ( P=0.04 ) were lower for MAX2 compared with MAX1 for both the EX30 and EX70 groups . It is concluded that performing a second bout of eccentric exercise with damaged muscles 3 days after the initial bout does not produce further damage or retard recovery , even when the second bout of exercise is more strenuous . EMG findings were consistent with reduced activation of fast-twitch motor units during the second eccentric bout . These results may be interpreted as evidence of a neural protective mechanism PURPOSE We examined the effects of short-term beta-hydroxy-beta-methylbutyrate ( HMB ) supplementation on symptoms of muscle damage following an acute bout of eccentric exercise . METHODS Non-resistance trained subjects were r and omly assigned to a HMB supplement group ( HMB , 40mg/kg bodyweight/day , n = 8) or placebo group ( CON , n = 9 ) . Supplementation commenced 6 days prior to a bout of 24 maximal isokinetic eccentric contractions of the elbow flexors and continued throughout post-testing . Muscle soreness , upper arm girth , and torque measures were assessed pre-exercise , 15 min post-exercise , and 1 , 2 , 3 , 4 , 7 , and 10 days post-exercise . RESULTS No pre-test differences between HMB and CON groups were identified , and both performed a similar amount of eccentric work during the main eccentric exercise bout ( p > .05 ) . HMB supplementation had no effect on swelling , muscle soreness , or torque following the damaging eccentric exercise bout ( p > .05 ) . CONCLUSION Compared to a placebo condition , short-term supplementation with 40mg/kg bodyweight/day of HMB had no beneficial effect on a range of symptoms associated with eccentric muscle damage . If HMB can produce an ergogenic response , a longer preexercise supplementation period may be necessary There is growing evidence that reactive oxygen species ( ROS ) are involved in the muscular damage and soreness that is observed following strenuous or unaccustomed exercise . This study investigated the relationship between  delayed onset muscle soreness ( DOMS )  , muscle function and ROS following downhill running using electron spin resonance ( ESR ) spectroscopy and plasma malonaldehyde ( MDA ) concentrations . Eight physically active male subjects participated in two trials consisting of 30 min of running at ~65 % V̇O2max on the flat ( FLA ) or a 15 % downhill ( DWN ) gradient . Venous blood sample s were drawn before , immediately after , and then 24 , 48 and 72 h post exercise , and at the same time DOMS and muscle function were assessed . Blood was analysed for markers of ROS , total and differential white blood cell count , and creatine kinase . Muscle function was measured on an isokinetic dynamometer , whilst DOMS was assessed using a visual analogue scale . An increase in ROS , detected via ESR spectroscopy and MDA , was observed following DWN ( P<0.05 ) but not following FLA . Increased DOMS and loss of muscle function were observed following DWN ( P<0.05 ) but not following FLA ( P>0.05 ) . DWN result ed in a transient leukocytosis ( P<0.05 ) occurring immediately post-exercise but returning to pre-exercise levels by 24 h. Although DWN result ed in an increase in ROS production , the increase occurred after the peak decline in muscle function and DOMS , suggesting that there may be a disassociation in the temporal relationship between ROS , loss of muscle function and DOMS This investigation evaluated the effects of oral creatine ( Cr ) supplementation on markers of exercise-induced muscle damage following high-force eccentric exercise in subjects r and omly administered Cr or placebo ( P ) in a double-blind fashion . When injected , exogenous phosphocreatine has been shown to stabilize the muscle membrane in cardiac tissue and enhance recovery of strength and power following injury . Twenty-three men aged 18–36 years ingested either 20 g of Cr or P for 5 days . Criterion measures were maximal isometric force of the elbow flexors ( MIF ) , range of motion ( ROM ) about the elbow , mid and distal arm circumference ( CIR ; to assess swelling ) , soreness with movement and palpation ( SOR ) , and blood levels of creatine kinase ( CK ) and lactate dehydrogenase ( LDH ) . Following the supplementation period , subjects performed 50 maximal eccentric contractions of the elbow flexors . Criterion measures were assessed pre-exercise , immediately postexercise , and for 5 days after exercise . Both groups experienced a significant loss of MIF and ROM ( time effect , p < 0.05 ) . There was a significant increase in CIR of the mid and distal biceps , SOR with movement and palpation , CK , and LDH ( time effect , p < 0.05 ) , indicating that there was significant muscle damage . However , there were no significant differences in any of the criterion measures between groups ( group χ time interaction term , p > 0.05 ) . The pattern of change over the 6 days , in response to the eccentric exercise , was nearly identical between groups . These data suggest that 5 days of Cr supplementation does not reduce indirect markers of muscle damage or enhance recovery from high-force eccentric exercise This study developed an electrical stimulation model for human elbow flexors to examine eccentric exercise-induced muscle damage and adaptation . Male students ( n=17 ) were r and omly placed into one of two groups ; isometric ( ES-ISO , n=8 ) and eccentric ( ES-ECC , n=9 ) . The elbow joint was fixed at 90 degrees ( 1.57 rad ) and the elbow flexors stimulated percutaneously by an electronic muscle stimulator for 5 s through two electrodes placed over the muscles for ES-ISO . In ES-ECC , the muscles were stimulated similarly to the ES-ISO , but the elbow joint was forcibly extended from an elbow flexed ( 90 degrees 1.57 rad ) to a full-extended position ( 180 degrees , 3.14 rad ) in 3 s. Maximal voluntary isometric force , range of motion , upper arm circumference , muscle thickness by ultrasonography , muscle soreness , plasma creatine kinase and aspartate aminotransferase activities were assessed before and for 4 days after exercise . ES-ECC produced significantly larger changes in all criterion measures compared with ES-ISO ( P < 0.01 ) . These findings confirmed that eccentric muscle actions induced muscle damage , but isometric contractions result ed in little or no damage . Six subjects from the ES-ECC group repeated the same eccentric exercise ( ECC2 ) 2 weeks after the first bout ( ECC1 ) , and changes in the criterion measures were compared between the bouts . Changes in all criterion measures after ECC2 were significantly smaller than ECC1 ( P < 0.01 ) . These results suggest that the first eccentric exercise produced a protective effect against muscle damage in the subsequent eccentric exercise bout , which does not involve adaptations in the central nervous system The study 's objective was to determine whether orally ingested caffeine could help overcome excitation-contraction-coupling failure , which has been suggested to explain part of the strength loss associated with eccentric-contraction-induced muscle injury . A sample of 13 college students ( 4 men and 9 women ) was used in a double-blind , repeated- measures experimental design . Each participant performed 2 experimental trials , 1 with each leg , with each trial lasting 4 consecutive days . On a given day , each participant was r and omly assigned to ingest a capsule containing 6 mg/kg of either caffeine or flour ( placebo ) . On the day of and the first 2 days after a bout of 50 injurious eccentric contractions done by the knee extensors , the interpolated-twitch technique was used to assess electrically evoked strength , maximal voluntary isometric contraction ( MVIC ) strength , and percent muscle activation during MVIC both before and after capsule ingestion . These variables were also measured before and after capsule ingestion the day before the eccentric-contraction bout -- when the muscle was uninjured . In injured muscle , caffeine had no effect on any variable . In uninjured muscle , caffeine also had no effect on electrically evoked strength but increased MVIC strength by 10.4 % compared with placebo ( p = .00002 ) , and this was attributed to an increase in muscle activation ( 6.2 % ; p = .01 ) . In conclusion , the data provide no evidence that caffeine ingestion can help overcome excitation-contraction-coupling failure , if it exists , in injured human muscle . The data do indicate that caffeine ingestion can increase MVIC strength and activation in uninjured muscle but not in injured muscle Percutaneous electrical myostimulation ( PES ) was used to manipulate the force produced by the knee extensor muscles during eccentric exercise , thereby providing a model to investigate the role of force in muscle damage . Two eccentric exercise bouts of equal work were performed by nine subjects , using fixed voltage PES at 20 Hz ( to produce moderate muscle forces ) and 100 Hz ( to produce high muscle forces ) . Muscle contractility , serum creatine kinase activity ( CK ) and muscle soreness ( MS ) were evaluated before , and up to 14 days after exercise . Data are presented as means+/-SEM , and were analysed using repeated measures analysis of variance ( ANOVA ) , t-tests and Wilcoxon tests . Peak forces were higher during the 100 Hz bout than the 20 Hz bout for repetitions 1 ( 472+/-60 vs 237+/-23 Newtons ) , 10 ( 381+/-26 vs 233+/-26 Newtons ) , 20 ( 310+/-24 vs 218+/-24 Newtons ) , all p < 0.01 , t-test and 30 ( 297+/-27 vs 204+/-21 Newtons ) , p < 0.05 , t-test . Following the 100 Hz bout , maximum voluntary contractile force ( MVC ) was lower ( p<0.01 , ANOVA ) , and CK was higher ( p<0.0001 , ANOVA ) than after the 20 Hz bout . Subjects also reported greater MS on days 2 to 6 ( p<0.05 , Wilcoxon test ) following the 100 Hz bout . Despite a decline in the stimulated 20:100 Hz tetanic force ratio after each bout ( p<0.01 , ANOVA ) there was no difference between bouts ( p>0.05 , ANOVA ) . The higher rise in CK and MS after the 100 Hz bout , together with the greater deficit in MVC , suggest that in humans , muscle force is a contributing factor to muscle injury during eccentric actions The purpose of this study was to determine the effects of antioxidant therapy on indirect markers of muscle damage following eccentric exercise ( EE ) . Eighteen women were r and omized to an antioxidant supplement or a placebo before a bout of EE . Plasma creatine kinase ( CK ) activity , muscle soreness ( MS ) , maximal isometric force ( MIF ) , and range of motion ( ROM ) were assessed before and through 14 d postexercise . Eccentric exercise result ed in an increase in CK activity and MS , and a drop in MIF and ROM during the days following EE , which returned to baseline values 14 d after EE in both groups . Antioxidants attenuated the CK activity and MS response to the EE , while little difference was noted between groups in MIF or ROM . These findings suggest that antioxidant supplementation was helpful in reducing the elevations in plasma CK activity and MS , with little impact on MIF and ROM loss Chatzinikolaou , A , Fatouros , IG , Gourgoulis , V , Avloniti , A , Jamurtas , AZ , Nikolaidis , MG , Douroudos , I , Michailidis , Y , Beneka , A , Malliou , P , Tofas , T , Georgiadis , I , M and alidis , D , and Taxildaris , K. Time course of changes in performance and inflammatory responses after acute plyometric exercise . J Strength Cond Res 24(5 ) : 1389 - 1398 , 2010-The objectives of the present investigation were to study the inflammatory and performance responses after an acute bout of intense plyometric exercise during a prolonged recovery period . Participants were r and omly assigned to either an  experimental group ( P , n = 12 ) that performed intense plyometric exercises or a  control group ( C , n = 12 ) that rested . The delayed onset of muscle soreness ( DOMS ) , knee range of motion ( KROM ) , creatine kinase ( CK ) and lactate dehydrogenase ( LDH ) activities , white blood cell count , C reactive protein ( CRP ) , uric acid ( UA ) , cortisol , testosterone , IL-6 , IL-1b strength ( isometric and isokinetic ) , and countermovement ( CMJ ) and static ( SJ ) jumping performance were measured at rest , immediately postexercise and at 24 , 48 , 72 , 96 , and 120 hours of recovery . Lactate was measured at rest and postexercise . Strength remained unchanged throughout recovery , but CMJ and SJ declined ( p < 0.05 ) by 8 - 20 % . P induced a marked rise in DOMS , CK , and LDH ( peaked 24 - 48 hours postexercise ) and a KROM decline . An acute-phase inflammatory response consisting of leukocytosis ( postexercise and at 24 hours ) , an IL-6 , IL-1b , CRP , and cortisol elevation ( during the first 24 hours of recovery ) and a delayed increase of UA ( peaked at 48 hours ) and testosterone ( peaked at 72 hours ) was observed in P. The results of this investigation indicate that performing an acute bout of intense plyometric exercise may induce a short-term muscle damage and marked but transient inflammatory responses . Jumping performance seems to deteriorate for as long as 72 hours postexercise , whereas strength appears to remain unchanged . The acute-phase inflammatory response after a plyometric exercise protocol appears to follow the same pattern as in other exercise models . These results clearly indicate the need of sufficient recovery between successive plyometric exercise training sessions There is evidence that protein hydrolysates can speed tissue repair following damage and may therefore be useful for accelerating recovery from exercise induced muscle damage . The potential for a hydrolysate ( WPI(HD ) ) of whey protein isolate ( WPI ) to speed recovery following eccentric exercise was evaluated by assessing effects on recovery of peak isometric torque ( PIT ) . In a double-blind r and omised parallel trial , 28 sedentary males had muscle soreness ( MS ) , serum creatine kinase ( CK ) activity , plasma TNFalpha , and PIT  assessed at baseline and after 100 maximal eccentric contractions ( ECC ) of their knee extensors . Participants then consumed 250 ml of flavoured water ( FW ; n=11 ) , or FW containing 25 g WPI ( n=11 ) or 25 g WPI(HD ) ( n=6 ) and the assessment s were repeated 1 , 2 , 6 and 24h later . PIT decreased approximately 23 % following ECC , remained suppressed in FW and WPI , but recovered fully in WPI(HD ) by 6h ( P=0.006 , treatment x time interaction ) . MS increased following ECC ( P<0.001 for time ) , and remained elevated with no difference between groups ( P=0.61 ) . TNFalpha and CK did not change ( P>0.45 ) . WPI(HD ) may be a useful supplement for assisting athletes to recover from fatiguing eccentric exercise 1 . It is known that a period of eccentric exercise provides protection against damage to muscle from subsequent eccentric exercise . Here we ask , does concentric exercise do the opposite , make muscle more prone to damage ? 2 . The triceps surae muscle group of one leg in each of eight human subjects was subjected to 30 min of concentric exercise per day , for 5 days . At the end of the training period there was a small but significant increase in passive torque in the exercised muscle ( P < 0.05 ) , with no changes in the untrained muscle . 3 . After a single period of eccentric exercise , angle-torque curves for muscles of both legs shifted in the direction of longer muscle lengths , suggestive of an increase in series compliance . The shift in the concentrically trained muscle was significantly greater over the first 48 h post-exercise ( P < 0 . 05 ) . 4 . The volume of the trained leg increased significantly more than the untrained leg for five subjects over 72 h post-exercise ( P < 0.05 ) . Peak torque fell , passive stiffness increased and both muscles became sore , but with no significant differences between the two legs . 5 . It is concluded that a period of concentric exercise increases the susceptibility of muscle to changes associated with the damage from eccentric exercise 1 . The effect of muscle length on the development of muscle pain and fatigue has been studied . 2 . Eight normal young adults performed maximal eccentric contractions of the elbow flexors . The muscles of one arm were exercised at short length , and the contralateral muscle at long length . Each contraction lasted approximately 1 s , and was repeated once every 10 s for 30 min . 3 . Muscle strength and frequency-force characteristics were measured from isometric contractions before , immediately after and at 24 h intervals for the next 4 days . Muscle tenderness was assessed daily . 4 . The muscle strength was reduced by approximately 10 % by exercise at short length , and by 30 % by exercise at long length . 5 . The 20:100 ratio ( force generated by stimulation at 20 Hz/force generated at 100 Hz ) fell by 30 % after exercise at short length and had recovered after 24 h. Exercise at long length reduced this ratio by 65 % and the muscles had not fully recovered 4 days later . 6 . Muscle pain developed after both exercise regimens , but was slightly worse after that at long length . 7 . It is concluded that there is a length-dependent component in the development of pain and fatigue after eccentric exercise , which had previously been thought to be caused solely by high force generation Muscle ultrastructure and contractile properties were examined before and after a single bout of resistance exercise ( 8 sets of 8 repetitions at 80 % of 1 repetition maximum ) . Eight untrained males performed the concentric ( Con ) phase of arm-curl exercise with one arm and the eccentric ( Ecc ) phase with the other arm . Needle biopsies were obtained from biceps brachii before exercise ( Base ) , immediately postexercise from each arm ( post-Con and post-Ecc ) , and 48 h postexercise from each arm ( 48 h-Con and 48 h-Ecc ) . Electron microscopy was used to quantify the presence of disrupted fibers in each sample . Analysis of variance revealed a greater ( P < or = 0.05 ) proportion of disrupted fibers in post-Con , post-Ecc , 48 h-Con , and 48 h-Ecc sample s compared with Base . Significantly more fibers were disrupted in post-Ecc ( 82 % ) and 48 h-Ecc ( 80 % ) sample s compared with post-Con ( 33 % ) and 48 h-Con ( 37 % ) , respectively . Voluntary and evoked strength measurements recovered to Base values within 24 h in the Con arm but remained depressed ( P < or = 0.05 ) for 72 - 96 h in the Ecc arm . These data indicate that both the raising and lowering phases of weightlifting produced myofibrillar disruption , with the greatest disruption occurring during the lowering phase CONTEXT Whether muscle warming protects against exercise-induced muscle damage is unknown . OBJECTIVE To determine the effect of leg immersion in warm water before stretch-shortening exercise on the time course of indirect markers of exercise-induced muscle damage . DESIGN Crossover trial . SETTING Human kinetics laboratory . PATIENTS OR OTHER PARTICIPANTS Eleven healthy , untrained men ( age = 21.5 + /- 1.7 years ) . INTERVENTION(S ) Participants ' legs were immersed in a water bath at 44 + /- 1 degrees C for 45 minutes . MAIN OUTCOME MEASURE(S ) Creatine kinase changes in the blood , muscle soreness , prolonged ( within 72 hours ) impairment in maximal voluntary contraction force and height of drop jump , and electrically evoked muscle force at low and high stimulation frequencies at short and long muscle lengths . RESULTS Leg immersion in warm water before stretch-shortening exercise reduced most of the indirect markers of exercise-induced muscle damage , including creatine kinase activity in the blood , muscle soreness , maximal voluntary contraction force , and jump height . The values for maximal voluntary contraction force and jump height , however , were higher during prewarming than for the control condition at 48 hours after stretch-shortening exercise , but this difference was only minor at other time points . Muscle prewarming did not bring about any changes in the dynamics of low-frequency fatigue , registered at either short or long muscle length , within 72 hours of stretch-shortening exercise . CONCLUSIONS Leg immersion in warm water before stretch-shortening exercise reduced most of the indirect markers of exercise-induced muscle damage . However , the clinical application of muscle prewarming may be limited , because decreasing muscle damage did not necessarily lead to improved voluntary performance Abstract We tested the hypothesis that exercise-induced muscle damage would increase the ventilatory ( [ Vdot ] E ) response to incremental/ramp cycle exercise ( lower the gas exchange threshold ) without altering the blood lactate profile , thereby dissociating the gas exchange and lactate thresholds . Ten physically active men completed maximal incremental cycle tests before ( pre ) and 48 h after ( post ) performing eccentric exercise comprising 100 squats .  Pulmonary gas exchange was measured breath-by-breath and fingertip blood sample d at 1-min intervals for determination of blood lactate concentration . The gas exchange threshold occurred at a lower work rate ( pre : 136 ± 27 W ; post : 105 ± 19 W ; P < 0.05 ) and oxygen uptake ( [Vdot]O2 ) ( pre : 1.58 ± 0.26 litres · min−1 ; post : 1.41 ± 0.14 litres · min−1 ; P < 0.05 ) after eccentric exercise . However , the lactate threshold occurred at a similar work rate ( pre : 161 ± 19 W ; post : 158 ± 22 W ; P > 0.05 ) and [Vdot]O2 ( pre : 1.90 ± 0.20 litres · min−1 ; post : 1.88 ± 0.15 litres · min−1 ; P > 0.05 ) after eccentric exercise . These findings demonstrate that exercise-induced muscle damage dissociates the [ Vdot ] E response to incremental/ramp exercise from the blood lactate response , indicating that [ Vdot ] E may be controlled by additional or altered neurogenic stimuli following eccentric exercise . Thus , due consideration of prior eccentric exercise should be made when using the gas exchange threshold to provide a non-invasive estimation of the lactate threshold
target: Conclusion Overall , our findings do not support the presence of a secondary loss of strength following an acute muscle injury , and strongly suggest that strength , on average , recovers steadily over the first 3 days post-injury
background: Background An immediate loss of strength follows virtually all types of muscle injury but there is debate whether the initial strength loss is maximal or if a secondary loss of strength occurs during the first 3 days post-injury .
  Objective The objective of this analysis was to conduct a systematic review and meta- analysis of the research literature to determine if a secondary loss of strength occurs after an injurious initiating event .