after maximal exercise , the purpose of the 
 recovery period is to rest the organism or return to conditions before the exercise . 
 recovery also accelerates the regeneration rate of the organism between training sessions 
 and decreases fatigue and injury risk . therefore , recovery or resting starts with the decrease of 
 lactic acid in the body . removal of lactic acid , which is eliminated in blood and muscle , 
 occurs over a period of approximately 2 hours with passive recovery and over a period of 1 
 hour on average with active recovery after maximal exercise1 . skeletal muscle contraction is classified in the literature as 
 isometric contraction , concentric contraction , and eccentric contraction . in eccentric 
 contraction , the load torque is greater than the muscle torque , and the muscle lengthens . in 
 contrast , the muscle torque is greater than the load torque in concentric contraction , and 
 the muscle length shortens2 . some studies 
 in the literature have demonstrated that eccentric exercises lead to strength losses , while , 
 others have shown different results because of the effects of exercise intensity , exercise 
 type ( resistance , downhill running ) , and area where the exercise is implemented3 , 4 . in addition to this , it can 
 therefore be seen that mechanical stress per fibril during eccentric exercises is higher 
 than that during concentric exercise . however , concentric exercise also causes more energy 
 expenditure , and it leads to more maximal contraction , lactic acid , and heart rate responses 
 compared with eccentric loading6,7,8 . eccentric contraction has been shown to produce greater muscle hypertrophy than a 
 concentric contraction after resistance training9 . in addition to greater hypertrophy , eccentric contraction training 
 tends to exert lower stress on the cardiovascular system10 . in contrast to eccentric training , the cardiovascular and 
 metabolic responses show a linear increase in concentric running11 . it has been stated that this difference can be associated 
 with the contribution of gravity during eccentric exercise . furthermore , it is understood 
 that gravitational force increasingly assists with the work of performing the activity as 
 the negative slope becomes steeper , thus reducing the physiologic work required of the 
 body11 . as a result of this , negative 
 slope walking e.g. , walking downhill may be associated with cardiovascular or metabolic 
 stress11 . the aim of this study was to 
 compare the differences in recovery periods after maximal concentric and eccentric exercises 
 between athletes and sedentary individuals . all measurements were performed in the 
 department of physiotherapy and rehabilitation , gazi university faculty of health sciences , 
 in a temperature - controlled performance laboratory . all participants were notified of the 
 research procedures , requirements , benefits , and risks before giving informed consent . 
 written informed consent the study was approved by 
 the research ethics committee of gazi university and was conducted in a manner consistent 
 with the institutional ethical requirements for human experimentation in accordance with the 
 declaration of helsinki . all measurements were performed by the same researchers at a 
 similar time of the day between 8:00 and 12:00 a.m. participants were asked not to exercise 
 exhaustively on the day prior to assessment and to have eaten and to be hydrated on the day 
 of the test . after excluding chronic or acute health conditions , musculoskeletal system 
 problems , and any drug intake , that might affect performance . the participants were divided into two groups : the athlete group 
 and the sedentary group . the athlete group trained on average 2 hours / day a least 4 
 days / week , whereas the sedentary group performed no training and had no lifestyle changes 
 during the study . all the players completed an incremental treadmill test on a motorized treadmill ( cosmed , 
 italy ) at an incline of 10% until exhaustion . the test began at 8  km.h , and the 
 speed was increased by 1  km.h every 3 minute until exhaustion . heart rate was monitored 
 continuously throughout the test and passive recovery session with a polar rs400 heart rate 
 monitor ( polar , finland ) . the heart rate data were transferred to a computer and smoothed 
 ( average of 1 second ) by the polar precision performance software ( ppp4 , finland ) . during 
 the passive recovery session , the venous blood lactate level ( la ) was determined every 3 
 minutes until it reached 2  mmol / l . differences in all test performance 
 variables between the athlete and sedentary groups were by nonparametric wilcoxon signed 
 rank tests for independent samples . all statistical analyses were performed in spss version 
 16.0 , and the level of statistical significance was set at p<0.05 . table 1table 1.descriptive characteristics of participantsathletesedentaryage ( years)22.1  3.320.1  1.1height ( cm)176  0.5174  0.0weight ( kg)73.4  6.465.9  8.6bmi ( kg / m)23.5  1.221.8  3.0 shows the descriptive characteristics of the subjects . table 2table 2.comparison of running durations , recovery durations , post - recovery heart rates , 
 and post - exercise lactic acid values within the groupsathlete(concentric loading)(+10%)athlete(eccentric loading)(10%)sedentary(concentric loading)(+10%)sedentary(eccentric loading)(10%)running duration ( min)17.1  0.945.0  2.7 * 10.8  1.326.1  0.9*recovery duration ( min)40.1  9.535.0  18.941.3  7.436.1  20.3heart rate ( rate / min)80.1  7.775.7  6.6101.9 11.9100.1  20.2lactic acid ( mmol / l)10.8  1.64.3  1.2 * 11.0  2.45.7  1.7**p<0.05 shows comparisons of the running durations , recovery durations , post - recovery 
 heart rates , and post - exercise lactic acid values within the groups . significant differences 
 were found between concentric and eccentric loading in the athlete group in terms of running 
 duration ( 17.1  0.9 vs. 45.0  2.7 ; z=2.80 , p=0.00 ) and la values ( 10.8  1.6 vs. 4.3  
 1.2 ; z=2.80 , p=0.00 ) . similarly , significant differences were found between concentric and 
 eccentric loading in the sedentary group in terms of running duration ( 10.8  1.3 vs. 26.1  
 0.9 ; z=2.80 , p=0.00 ) and la values ( 11.0  2.4 vs. 5.7  1.7 ; z=2.80 , p=0.00 ) . table 3table 3.comparison of running durations , recovery durations , post - recovery heart rates , 
 and post - exercise lactic acid values between the groupsathlete(concentric loading)(+10%)sedentary(concentric loading)(+10%)athlete(eccentric loading)(10%)sedentary(eccentric loading)(10%)running duration ( min)17.1  0.910.8  1.3 * 45.0  2.726.1  0.9*recovery duration ( min)40.1  9.541.3  7.435.0  18.936.1  20.3heart rate ( rate / min)80.1  7.7101.9  11.9 * 75.7  6.6100.1  20.2*lactic acid ( mmol / l)10.8  1.611.0  2.44.3 1.25.7  1.7*p<0.05 shows comparisons of the running durations , recovery durations , post - recovery 
 heart rates , and post - exercise lactic acid values between the groups . significant 
 differences in concentric loading were found between the athlete and sedentary groups in 
 terms of running duration ( 17.1  0.9 vs. 10.8  1.3 ; z=3 . 65 , p=0.00 ) and post - recovery hr 
 responses ( 80.1  7.7 vs. 101.9  11.9 ; z=3.63 , p=0.00 ) . similarly , significant differences 
 in eccentric loading were found between the athlete and sedentary groups in terms of running 
 duration ( 45.0  2.7 vs. 26.1  0.9 ; z=3 . 07 , p=0.00 ) and post - recovery hr responses ( 75.7 
  6.6 vs. 100.1  20.2 ; z=2.82 , p=0.00 ) . the aim of this study was to compare the differences in recovery periods after maximal 
 concentric and eccentric exercises . one of the main findings of the present study is that 
 the post - exercise la responses are significantly higher with concentric loading compared 
 with eccentric loadings . however , the athlete group had a significantly lower running 
 duration with concentric loading . both the athlete and sedentary groups tolerated eccentric 
 loading better in terms of running durations and post - exercise lactic acid levels . as la and 
 h+ are removed from blood via oxidation12 , the type of the recovery significantly affects the elimination of la 
 from blood13 . studies have repored that 
 anaerobic energy metabolism , an important part of recovery session , is closely associated 
 with the elimination of la from muscle and blood after high intensity activities14 , 15 . the elimination of la from muscle and blood after a maximal exercise 
 occurs over a period of approximately 2 hours with passive rest and over a period of 1 hour 
 on average with active rest1 . several 
 studies have demonstrated that active recovery is a more effective strategy for eliminating 
 of la from muscle and blood and subsequent exercise performance compared with other recovery 
 strategies16,17,18 . active recovery allows 
 greater reoxygenation of myoglobin and therefore oxygen delivery to the muscles19 . therefore , recovery strategies are of 
 crucial importance for subsequent performance or loading after maximal or supramaximal 
 loading . our results showed that no significant difference was observed in an intragroup comparison 
 made between + 10% and 10% slopes in post - exercise recovery durations and post - recovery hr 
 of the athletes , while significant differences were detected in running durations and 
 post - exercise la values in the athlete and control groups . this may explain why the athlete 
 group tolerated exercise better in both loading types and they recovered more efficiently 
 after the end of the exercise . a previous study showed that passive recovery strategies 
 showed no advantages in recovery except for after high intensity exercise with a recovery 
 period of less than 3 minutes20 . for 
 these reasons , active resting is advisable if the recovery period is longer than 34 minutes 
 after high intensity exercise . moreover , many studies have shown that elimination of la and 
 post - exercise hr responses are correlated with aerobic capacity21 . low - intensity exercise effectively increases endurance 
 capacity , but it does not effectively induce hypertrophy of the skeletal muscle22 . in contrast , several studies have shown 
 that capacity of the endurance affects muscle lactate concentration and lactate elimination 
 after maximal loading23,24,25 . another study 
 showed that the ability to eliminate lactate increases in workout endurance exercises during 
 active recovery18 . in addition , endurance 
 exercises reduce lactate production and increase the removal of lactate26 . in contrast , no differences were found between trained 
 and sedentary people in terms of la during passive recovery after exhaustive exercise15 . it is known that aerobic training , which improves maximal oxygen uptake and 
 oxidative capacity , increases the activity of aerobic enzymes and mitochondrial and 
 capillary densities in muscles27 , is one 
 of the most common and popular activities among adults of all ages , decreasing the resting 
 hr5 and shortening the post - exercise 
 recovery phase28 . in addition , it was 
 found that the recovery of hr within 30 seconds after exercise is negatively correlated with 
 the pre - exercise levels29 . the present study also showed that running duration and post - recovery hr responses were 
 significantly higher in after concentric loading in the athlete group compared with the 
 sedentary group . additionally , passive recovery had an effect on running duration and 
 post - recovery hr responses , and the athlete group had a significantly lower running duration 
 and post - recovery hr responses after eccentric loadings . this can be explained by the 
 positive physiological effect on athletes of training for a long time . many activities of 
 daily living use muscle combinations that require the coordinated use of concentric and 
 eccentric contractions11 . however , it is 
 known that long - term eccentric contractions generate acute pains and reduction in functional 
 strength in the sedentary individuals . nevertheless , it can be possible to continue 
 exercise , especially exercise in the form of downhill running for a long time without tiring 
 with the contribution of gravity11 . after 
 two different styles of aerobic loading , that is , walking and jogging for men and women on 
 5% and 10% and + 5% and + 10% slopes respectively , were found lower heart rates responses 
 found for both groups on the 5% and 10% slopes30 . both the athlete and sedentary groups continued the running 
 exercise on the 10% slopes under eccentric loading for longer and completed running with a 
 lower lactic acid level in our study as well . in conclusion , athletes continued to exercises for a longer duration at a higher intensity 
 under both concentric and eccentric loading . it was observed that concentric exercise led to 
 more la accumulation and higher hr responses . although there was no difference between the 
 athlete and sedentary groups as a result of eccentric and concentric loadings in terms of 
 recovery durations , it was observed that athletes recovered faster in terms of hr . in 
 addition , both the athlete and sedentary groups performed eccentric running for longer under 
 all loading conditions . this fact 
 demonstrates that athletes tolerate eccentric exercise better due to the contribution of 
 gravity . the contribution of regular aerobic workouts to the recovery period was 
 demonstrated in this study . however , it was observed that these effects were limited with a 
 passive recovery period . the results of this study suggest that people who wish to 
 derive more benefits from training should pay special attention to choosing the exercise 
 type and should consider their health profile . in addition , eccentric exercises are more 
 effective for improving muscle size and gaining strength in healthy individuals .
[ purpose ] the aim of this study was to compare the differences in recovery 
 periods after maximal concentric and eccentric exercises . [ subjects and methods ] 
 twenty - two participants voluntarily participated and were divided into two groups : the 
 athlete and sedentary groups . 
 an incremental treadmill running test was performed until 
 exhaustion . during the subsequent passive recovery session , heart rate and venous blood 
 lactate level were determined every 3 minutes until the venous blood lactate level reached 
 2  mmol / l . 
 the same test protocol was implemented 15 days later . 
 [ results ] both groups 
 showed significantly shorter running durations in concentric exercise , while significant 
 differences were found between the athlete and sedentary groups in terms of venous blood 
 lactate level responses . 
 in addition , there were significant differences between the 
 athlete and sedentary groups in terms of running duration and heart rate in concentric and 
 eccentric exercises . 
 [ conclusion ] the present study revealed no difference between the 
 athlete and sedentary groups in terms of recovery durations after eccentric and concentric 
 loadings , although the athletes demonstrated faster recovery in terms of hr compared with 
 the sedentary group . 
 it was thought that concentric exercises cause greater physiological 
 responses .