title: Grip and knee extension muscle strength reflect a common construct among adults. Attenuation of skeletal muscle and strength in the elderly: The Health ABC Study. Effects of Whole-Body Vibration on Muscle Architecture, Muscle Strength, and Balance in Stroke Patients: A Randomized Controlled Trial Are changes in leg power responsible for clinically meaningful improvements in mobility in older adults? Upper motor neuron lesions: their effect on muscle performance and appearance in stroke patients with minor motor impairment. Jump training is feasible for nearly ambulatory patients after stroke Muscle quality. I. Age-associated differences between arm and leg muscle groups. Reliability of concentric and eccentric torque during isokinetic knee extension in post-stroke hemiparesis. Plantarflexor weakness as a limiting factor of gait speed in stroke subjects and the compensating role of hip flexors. Association between ultrasound measurements of muscle thickness, pennation angle, echogenicity and skeletal muscle strength in the elderly
abstract: INTRODUCTION Both grip and knee extension strength are often used to characterize overall limb muscle strength . We sought to determine if the measures actually reflect a common construct . METHODS The isometric grip and knee extension strength of 164 healthy men and women ( range , 18 - 85 years ) were measured bilaterally using st and ard procedures . Pearson correlations ( r ) , Cronbach alpha , principal components analysis , and multiple regression/correlation were used to investigate the dimensionality of the measures . RESULTS Left and right grip forces and knee extension torques were highly correlated , internally consistent , and loaded on a single component . Gender and age explained the variance in both measures , but height added to the explanation of grip strength , whereas weight added to the explanation of knee extension strength . CONCLUSIONS Among healthy adults , grip and knee extension strength reflect a common underlying construct . The measures , however , are affected differently by height and weight Although loss of muscle mass is considered a cause of diminished muscle strength with aging , little is known regarding whether composition of aging muscle affects strength . The skeletal muscle attenuation coefficient , as determined by computed tomography , is a noninvasive measure of muscle density , and lower values reflect increased muscle lipid content . This investigation examined the hypothesis that lower values for muscle attenuation are associated with lower voluntary isokinetic knee extensor strength at 60 degrees/s in 2,627 men and women aged 70 - 79 yr participating in baseline studies of the Health ABC Study , a longitudinal study of health , aging , and body composition .  Strength was higher in men than in women ( 132.3 + /- 34.5 vs. 81.4 + /- 22.0 N x m , P < 0.01 ) . Men had greater muscle attenuation values ( 37.3 + /- 6.5 vs. 34.7 + /- 7.0 Hounsfield units ) and muscle cross-sectional area ( CSA ) at the midthigh than women ( 132.7 + /- 22.4 vs. 93.3 + /- 17.5 cm(2 ) , P < 0.01 for both ) . The strength per muscle CSA ( specific force ) was also higher in men ( 1.00 + /- 0.21 vs. 0.88 + /- 0.21 N x m x cm(-2 ) ) . The attenuation coefficient was significantly lower for hamstrings than for quadriceps ( 28.7 + /- 8.7 vs. 41.1 + /- 6.9 Hounsfield units , P < 0.01 ) . Midthigh muscle attenuation values were lowest ( P < 0.01 ) in the eldest men and women and were negatively associated with total body fat ( r = -0.53 , P < 0.01 ) . Higher muscle attenuation values were also associated with greater specific force production ( r = 0.26 , P < 0.01 ) . Multivariate regression analysis revealed that the attenuation coefficient of muscle was independently associated with muscle strength after adjustment for muscle CSA and midthigh adipose tissue in men and women . These results demonstrate that the attenuation values of muscle on computed tomography in older persons can account for differences in muscle strength not attributed to muscle quantity Objective The aim of the present study was to analyze the effects of whole-body vibration on lower limb muscle architecture , muscle strength , and balance in stroke patients during a period of 3 mos . Design The inclusion criteria were having had ischemic or hemorrhagic stroke at least 6 mos before the study and a National Institutes of Health Stroke Scale score of greater than 1 and less than 20 . The patients were r and omly divided into two groups : an  experimental group ( n = 11 , six men and five women ; age , 62.4 ± 10.7 yrs ; height , 1.64 ± 0.07 m ; mass , 69.4 ± 12.9 kg ) and a sham group ( n = 9 , five men and four women ; age , 64.4 ± 7.6 yrs ; height , 1.62 ± 0.07 m ; mass , 75.0 ± 15.8 kg ) . The experimental group received a whole-body vibration treatment , with an increase in frequency , sets , and time per set during 17 sessions . The sham group performed the same exercises as that of the experimental group but was not exposed to vibration . Outcome variables included the muscle architecture ( the rectus femoris , the vastus lateralis , and the medial gastrocnemius ) , the maximal isometric voluntary contraction of the knee extensors , and the Berg Balance Scale . Results There were no significant differences between the groups on the primary outcomes of lower limb muscle architecture , muscle strength , and balance . Conclusions It seems that whole-body vibration exercise does not augment the increase in neuromuscular performance and lower limb muscle architecture induced by isometric exercise alone in stroke patients OBJECTIVES From among physiological attributes commonly targeted in rehabilitation , to identify those in which changes led to clinical ly meaningful differences ( CMDs ) in mobility outcomes . DESIGN Secondary analysis of data collected for a r and omized controlled trial of exercise using binary outcomes defined by recording a large CMD ( Short Physical Performance Battery (SPPB)=1 unit ; gait speed (GS)=0.1 m/s ) . Iterative models were performed to evaluate possible confounding between physiological variables and relevant covariates . SETTING Outpatient rehabilitation centers . PARTICIPANTS Community-dwelling mobility-limited older adults ( n=116 ) participating in a 16-week r and omized controlled trial of two modes of exercise .  MEASUREMENTS Physiological measures included leg power , leg strength , balance as measured according to the Performance-Oriented Mobility Assessment ( POMA ) , and rate pressure product at the maximal stage of an exercise tolerance test . Outcomes included GS and SPPB . Leg power and leg strength were measured using computerized pneumatic strength training equipment and recorded in Watts and Newtons , respectively . RESULTS Participants were 68 % female , had a mean age of 75.2 , a mean of 5.5 chronic conditions , and a baseline mean SPPB score of 8.7 . After controlling for age , site , group assignment , and baseline outcome values , leg power was the only attribute in which changes were significantly associated with a large CMD in SPPB ( odds ratio (OR)=1.48 , 95 % confidence interval (CI)=1.09 - 2.02 ) and GS ( OR=1.31 , 95 % CI=1.01 - 1.70 ) . CONCLUSION Improvements in leg power , independent of strength , appear to make an important contribution to clinical ly meaningful improvements in SPPB and GS OBJECTIVE To evaluate muscular performance and appearance in patients with prior stroke who were ambulatory . DESIGN Nonr and omized study . SETTING University hospital laboratory . SUBJECTS Sixteen persons ( 11 men , 5 women ) with minor motor impairments , 6 to 24 months after stroke , were included . As reference , data were used from a population -based sample of 144 men and women . MAIN OUTCOME MEASUREMENTS Muscle performance was evaluated using a  Kin-Com dynamometer  in both the affected and the nonaffected leg . Peak isometric strength was measured at a 60 degree angle in both extension and flexion . Maximal isokinetic strength was measured at 60 degrees/sec and at 180 degrees/sec . Endurance was evaluated during isometric and dynamic knee extensions . Muscle biopsies were taken on nine patients and muscle tissue areas were determined with computed tomography . RESULTS The affected leg was weaker but not different in relative endurance compared with the nonaffected side . The performance of the nonaffected side was somewhat lower than that of a matched reference population . No major difference in fiber composition between the affected and nonaffected legs was noted , except for a lower degree of capillarization in the affected leg . CONCLUSION In well-functioning stroke patients with good motor performance , further muscle training that includes resistance exercise might be indicated Objective : To evaluate the feasibility of jump training for nearly ambulatory patients after stroke . Design : Case series . Setting : A rehabilitation centre for adult people with neurological disorders . Subjects : Six subacute , nearly ambulatory patients with hemiparesis due to stroke . Interventions : A modified form of jump training performed over a period of six weeks . Measures : Impairments : We used the Motricity Index to measure strength , the Fugl-Meyer subtest passive joint motion/pain for range of motion and pain and the modified Tardieu Scale to measure spasticity at baseline and after six weeks . Activity level : To assess walking ability we used the Functional Ambulation Category , to measure walking quality we used 10-m gait velocity , stride length and Rivermead Visual Gait Index and to assess walking capacity we used the six-minute walk test . Results : No severe adverse events were observed during the study period . Motricity Index sum score of the affected leg increased from 38±11 points ( mean±SD ) to 56±15 points ; P = 0.028 . Modified Tardieu Scale and Fugl-Meyer subtest passive joint motion/pain remained unchanged over time ( P=1.0 ; P=0.157 , respectively ) . All patients were able to walk at the end of training ( median Functional Ambulation Category grade five , P=0.023 ) . Gait quality improved as shown in increased gait velocity ( from 0.3±0.1 to 1.1±0.5 m/s ; P = 0.028 ) , improved stride length ( from 0.3±0.1 to 0.6±0.2 m ; P = 0.028 ) and improved Rivermead Visual Gait Index score ( from 38.7±5.6 points to 24.8±7.0 points ; P = 0.027 ) . All patient increased gait capacity ( from 97±33 m to 289±134 m ; P = 0.028 ) . Conclusion : Jump exercises are feasible for selected subacute stroke patients with hemiparesis To determine the differences between arm and leg muscle quality ( MQ ) across the adult life span in men and women , concentric ( Con ) and eccentric ( Ecc ) peak torque ( PT ) were measured in 703 subjects ( 364 men and 339 women , age range 19 - 93 yr ) and appendicular skeletal muscle mass ( MM ) was determined in the arm and leg in a subgroup of 502 of these subjects ( 224 men and 278 women ) . Regression analysis showed that MQ , defined as PT per unit of MM , was significantly higher in the arm ( approximately 30 % ) than in the leg across age in both genders ( P < 0.01 ) . Arm and leg MQ declined at a similar rate with age in men , whereas leg MQ declined approximately 20 % more than arm MQ with increasing age in women ( P < /= 0.01 and P < 0.05 for Con and Ecc PT , respectively ) . Moreover , the age-associated decrease in arm MQ was steeper in men than in women whether Con or Ecc PT was used ( both P < 0.05 ) . Arm MQ as determined by Con PT showed a linear age-related decline in men and women ( 28 and 20 % , respectively , P < 0.001 ) , whereas arm MQ as determined by Ecc PT showed a linear age-related decline in men ( 25 % , P < 0.001 ) but not in women ( not significant ) . In contrast , both genders exhibited an age-related quadratic decline in leg MQ as determined by Con PT ( approximately 40 % ) and Ecc PT ( approximately 25 % ; both P < 0.001 ) , and the rate of decline was similar for men and women . Thus MQ is affected by age and gender , but the magnitude of this effect depends on the muscle group studied and the type of muscle action ( Con vs. Ecc ) used to assess strength BACKGROUND Emerging evidence on the velocity-dependent nature of force impairment in post-stroke hemiparesis has emphasized the complexity of strength and motor performance assessment s in this clinical population . The need to establish reliability and responsiveness of muscle performance measures across a broad range of concentric and eccentric movement speeds is therefore clear , as these metrics will provide benchmarks both for making clinical inference and evaluating meaningful clinical change following interventions . METHODS Isokinetic knee extensor strength was tested at 14 angular velocities in 17 adults with chronic post-stroke hemiparesis ( > 18 months ) , and 13 non-disabled controls . Identical tests were conducted on two occasions separated by two days . Test-retest reliability of maximal isokinetic torque was evaluated using intraclass correlation . Absolute reliability was assessed using st and ard error of measurement from which smallest real differences were derived . FINDINGS Overall , intraclass correlation coefficients were excellent for both hemiparetic ( 0.891 ) and control ( 0.937 ) groups . Intraclass correlation coefficients for each criterion speed were also high for both groups ( > 0.86 ) . Measurement error relative to the mean torque varied between 14.1 % and 26.3 % for hemiparetic subjects and 6.0 - 18.1 % for controls . The smallest real difference relative to mean torque was 39.0 - 72.7 % and 16.6 - 50.2 % for hemiparetic and control subjects , respectively . INTERPRETATION Isokinetic knee extension torque can be measured reliably in persons with chronic post-stroke hemiparesis and in non-disabled controls across a full functional range of concentric and eccentric speeds . Established measurement error and smallest real differences will aid interpretation of longitudinal observations of muscle performance in this clinical population OBJECTIVE To determine , using the Muscular Utilization Ratio ( MUR ) method , whether plantarflexor weakness is among the factors preventing stroke subjects from walking at faster speeds . Potential compensations by the hip flexors were also examined . DESIGN A convenience sample of 17 chronic stroke subjects in a context of a descriptive study . BACKGROUND Gait speed is correlated with the residual strength of the muscles involved in gait in stroke subjects . However , it has not been established if this residual strength limits gait speed . METHODS  Kinetic and kinematic data for comfortable and maximal gait speeds were collected on the paretic side , and were used to determine the  moments in plantarflexion ( mechanical dem and : MUR numerator ) during the push-off phase . The maximal potential moment ( MUR denominator ) of the plantarflexors during gait was predicted using an equation derived from dynamometric data collected with a Biodex system . The MURs of the plantarflexors  were then calculated at every 1 % interval of the push-off phase . The pull-off phase of gait and the hip flexor strength were also examined . RESULTS Ten subjects of the sample had a MUR value between 80 and 150 % at maximal gait speed . These subjects produced the lowest peak torques in plantarflexion . Each of the four fastest subjects of this group had a large hip flexion moment during the pull-off phase of gait and produced high hip flexion torque values on the dynamometer . Each of the seven remaining subjects had a MUR value under 70 % when they walked at maximal speed . CONCLUSIONS Weakness of the plantarflexors should be considered as one factor limiting gait speed in 10 hemiparetic subjects . Some subjects with weak plantarflexors could walk rapidly because they compensated with the hip flexors . For the remaining stroke subjects , factors other than weakness of the plantarflexors have to be considered in order to explain the reduction in their gait speed The increase of elderly in our society requires simple tools for quantification of sarcopenia in inpatient and outpatient setting s. The aim of this study was to compare parameters determined with musculoskeletal ultrasound ( M-US ) with muscle strength in young and elderly patients . In this prospect i ve , r and omised and observer blind study , 26 young ( 24.2 ± 3.7 years ) and 26 old ( age 67.8 ± 4.8 years ) patients were included . Muscle thickness , pennation angle and echogenicity of all muscles of musculus quadriceps were measured by M-US and correlated with isometric maximum voluntary contraction force ( MVC ) of musculus quadriceps . Reproducibility of M-US measurements as well as simple and multiple regression models were calculated . Of all measured M-US variables the highest reproducibility was found for measurements of thickness ( intraclass correlation coefficients , 85–97 % ) . Simple regression analysis showed a highly significant correlation of thickness measurements of all muscles of musculus quadriceps with MVC in the elderly and in the young . Multiple regression analysis revealed that thickness of musculus vastus medialis had the best correlation with MVC in the elderly . This study showed that measurement of muscle thickness , especially of musculus vastus medialis , by M-US is a reliable , bedside method for monitoring the extent of sarcopenia
target: Conclusions : Age-related differences support the impact of stroke-related sarcopenia as a contributor to hemiparetic muscle dysfunction .
background: Abstract Background : Despite extensive study of the impact of stroke on muscle and functional performance , questions remain regarding the extent to which changes are due to the neurological injury vs. age-related loss of morphology and force production .
  Objectives : To synthesize available evidence describing post-stroke changes in lower extremity muscle size and strength compared to healthy adults .