Ankle force and rate of force production increase following high intensity strength training in frail older adults Evidence for improved muscle activation patterns after retraining of reaching movements with the MIME robotic system in subjects with post-stroke hemiparesis Task-oriented progressive resistance strength training improves muscle strength and functional performance in individuals with stroke Single Session of Transcranial Direct Current Stimulation Transiently Increases Knee Extensor Force in Patients With Hemiparetic Stroke Bed rest promotes reductions in walking speed, functional parameters, and aerobic fitness in older, healthy adults. Hip, thigh and calf muscle atrophy and bone loss after 5-week bedrest inactivity Reliability of concentric and eccentric torque during isokinetic knee extension in post-stroke hemiparesis. Forced use of hemiplegic upper extremities to reverse the effect of learned nonuse among chronic stroke and head-injured patients Muscle, functional and cognitive adaptations after flywheel resistance training in stroke patients: a pilot randomized controlled trial Progressive resistance training increases strength after stroke but this may not carry over to activity: a systematic review.
Background and aims : The most common cause of accidental injury and death in people over age 65 results from impacts associated with falling . Balance impaired older adults have poorer balance control than healthy young adults or healthy older adults . Lack of sufficient lower extremity strength and inability to rapidly produce muscle force may contribute to diminished balance control in the elderly . This study evaluated the effect of a 10-week high intensity strength- training program targeting key lower extremity muscles for the purpose of improving postural control in frail older adults . Methods : Thirteen experimental and fourteen control subjects , all balance impaired older adults were evaluated in response to unexpected platform perturbations that simulated slips . Results : Following strength training the experimental group was significantly stronger than the control group . Mean ankle moments improved in the experimental group following strength training during forward sway ( Right : p=0.067 , Left : p=0.009 ) and backward sway ( Right : p=0.031 , Left : p=0.058 ) . For the backward sway condition the ankle rate of torque production increased significantly in the experimental group ( Right : p=0.016 , Left : p=0.031 ) . Conclusions : Enhancement of lower extremity strength contributed to improvements in balance stability demonstrated by greater ankle force production , in response to balance threats Previously , we reported that chronic stroke subjects had significant improvements in isometric strength , free reaching extent , and clinical evaluations of function after training in the  mirror-image movement enabler ( MIME ) robotic device . Our primary goal in this analysis was to investigate the hypothesis that the robotic training promoted improved muscle activation patterns . To this end , we examined the interaction forces , kinematics , and electromyograms recorded during training of eight different movement patterns in active-constrained mode . In this mode , the robot constrained the reaching movements to be toward the target , and the movement velocity was proportional to the force produced along the trajectory . Thirteen chronic stroke subjects trained in MIME for 24 1-h sessions over an eight-week period . Work output was significantly increased by week five in all eight movement patterns . Low-level subjects increased their extent of reach , while high-level subjects increased their speed . Directional errors in force production were reduced in six of eight movement patterns . Electromyographic data provided evidence for improved muscle activation patterns in the four movement patterns that started at tabletop level and ended at shoulder level . In contrast , there was no evidence of improved muscle activation patterns in any of the tabletop movements , with increased activation of antagonists in two movement patterns . This dichotomy may have been related to compensation at the shoulder girdle during movements that remained at tabletop level . A simple biomechanical model will be introduced to demonstrate the likelihood of this possibility Objective : To examine the effectiveness of task-oriented progressive resistance strength training on lower extremity strength and functional performance in chronic stroke subjects . Design : Single-blind , r and omized controlled trial . Setting : Medical centre and district hospital . Subjects : Forty-eight subjects at least one year post stroke . Interventions : Participants r and omly allocated to two groups , control  ( n-/24 ) and experimental  ( n-/24 ) . Subjects in the control group did not receive any rehabilitation training . Subjects in the experimental group were put on a four-week task-oriented progressive resistance strength training . Main measures : Lower extremity muscle strength , gait velocity , cadence , stride length , six-minute walk test , step test , and timed up and go test . Results : Muscle strength significantly improved in the experimental group for strong side muscle groups ( ranged from 23.9 % to 36.5 % ) and paretic side muscle groups ( ranged from 10.1 % to 77.9 % ) . In the control group muscle strength changes ranged from 6.7 % gain to 11.2 % decline . The experimental group showed significant improvement in all selected measures of functional performance except for the step test . In the control group , the number of repetitions of the step test significantly decreased ( -20.3 % ) with no change in other functional tests . There was a significant difference between groups for muscle strength and all functional measures . The strength gain was significantly associated with gain in the functional tests . Conclusions : The task-oriented progressive resistance strength training programme could improve lower extremity muscle strength in individuals with chronic stroke and could carry over into improvement in functional abilities Background . Transcranial direct current stimulation ( tDCS ) of the motor cortex can enhance the performance of a paretic upper extremity after stroke . Reported effects on lower limb ( LL ) function are sparse . Objective . The authors examined whether tDCS can increase the force production of the paretic quadriceps . Methods . In this double-blind , crossover , sham-controlled experimental design , 8 participants with chronic subcortical stroke performed knee extension using their hemiparetic leg before , during , and after anodal or sham tDCS of the LL motor cortex representation in the affected hemisphere . Affected h and -grip force was also recorded . Results . The maximal knee-extension force increased by 21 N ( 13.2 % , P < .01 ) during anodal tDCS compared with baseline and sham stimulation . The increase persisted less than 30 minutes . Maximal h and -grip force did not change . Conclusions . Anodal tDCS transiently enhanced knee extensor strength . The modest increase was specific to the LL . Thus , tDCS might augment the rehabilitation of stroke patients when combined with lower extremity strengthening or functional training CONTEXT The exact relationship between the bed rest-induced loss of skeletal muscle and reductions in muscle strength and physical performance in the older individuals is still unclear . OBJECTIVE We examined the effect of 10 days of bed rest on changes in regional body composition , muscle strength , and functional status , and the relationship between these variables in older individuals . DESIGN , PARTICIPANTS , AND INTERVENTION Regional body composition was measured using dual energy x-ray absorptiometry . We also determined changes in leg strength and several indices of functional status , including walking speed . RESULTS Body weight , body mass index , and total and lower extremity lean mass decreased with bed rest . There were also significant reductions in knee extension one repetition maximum , isometric knee extension , knee extension 60 ° concentric , stair ascent time , stair ascent power , stair descent time , VO2 max , floor transfer test , 5-minute walk time , and chair st and . The overall change in total and lower extremity lean mass was also directly related to bed rest-induced reductions in one repetition maximum knee extension . CONCLUSIONS Bed rest promoted overall declines in muscle mass , muscle strength , and physical function in older individuals . The changes in lean tissue were closely correlated with the bed rest-induced decline of muscle strength Unloaded inactivity induces atrophy and functional deconditioning of skeletal muscle , especially in the lower extremities . Information is scarce , however , regarding the effect of unloaded inactivity on muscle size and function about the hip . Regional bone loss has been demonstrated in hips and knees of elderly orthopaedic patients , as quantified by computerized tomography ( CT ) . This method remains to be vali date d in healthy individuals rendered inactive , including real or simulated weightlessness . In this study , ten healthy males were subjected to 5 weeks of experimental bedrest and five matched individuals served as ambulatory controls . Maximum voluntary isometric hip and knee extension force were measured using the strain gauge technique .  Cross-sectional area ( CSA ) of hip , thigh and calf muscles , and radiological density ( RD ) of the proximal tibial bone were measured using CT . Bedrest decreased ( P < 0.05 ) average ( SD ) muscle strength by 20 (8)% in knee extension , and by 22 (12)% in hip extension . Bedrest induced atrophy ( P < 0.05 ) of extensor muscles in the gluteal region , thigh and calf , ranging from 2 to 12 % . Atrophy was more pronounced in the knee extensors [ 9 (4)% ] and ankle plantar flexors [ 12 (3)% ] than in the gluteal extensor muscles [ 2 (2)% ] . Bone density of the proximal tibia decreased ( P < 0.05 ) by 3 (2)% during bedrest . Control subjects did not show any temporal changes in muscle or bone indices ( P > 0.05 ) , when examined at similar time intervals . The present findings of a substantial loss in hip extensor strength and a smaller , yet significant atrophy of these muscles , demonstrate that hip muscle deconditioning accompanies losses in thigh and calf muscle mass after bedrest . This suggests that comprehensive quantitative studies on impaired locomotor function after inactivity should include all joints of the lower extremity . Our results also demonstrate that a decreased RD , indicating bone mineral loss , can be shown already after 5 weeks of unloaded bedrest , using a st and ard CT technique 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 To test the clinical counterpart of the learned nonuse theory , 25 chronic hemiplegic stroke and head-injured patients with minimal to moderate upper extremity extensor muscle function were required to keep their uninvolved upper extremities within a h and -enclosed sling during waking hours over a 2-week interval . During this forced use period and for 1 year thereafter , changes in force or time-based measures among 21 functional tasks were compared to values at the sixth baseline session , a preintervention time when relearning had plateaued . Significant ( P less than 0.05 , Friedman 's repeated measures followed by Tukey multiple comparison tests ) changes were seen in 19 of the 21 tasks with most persisting at the 1-year follow-up . There were no apparent differences between right- and left-sided involvement or between stroke versus head injury clients ( Mann-Whitney procedure ) . Ratings for quality of movement scored from videotapes presented in r and om order showed no change over time . These data suggest that learned nonuse does occur in select neurological patients and that this behavior can be reversed through application of a forced use paradigm Background Resistance exercise ( RE ) improves neuromuscular function and physical performance after stroke . Yet , the effects of RE emphasizing eccentric ( ECC ; lengthening ) actions on muscle hypertrophy and cognitive function in stroke patients are currently unknown . Thus , this study explored the effects of ECC-overload RE training on skeletal muscle size and function , and cognitive performance in individuals with stroke . Methods Thirty-two individuals with chronic stroke ( ≥6 months post-stroke ) were r and omly assigned into a training group ( TG ; n = 16 ) performing ECC-overload flywheel RE of the more-affected lower limb ( 12 weeks , 2 times/week ; 4 sets of 7 maximal closed-chain knee extensions ; < 2 min of contractile activity per session ) or a control group ( CG ; n = 16 ) , maintaining daily routines . Before and after the intervention , quadriceps femoris volume , maximal force and power for each leg were assessed , and functional and dual task performance , and cognitive functions were measured . Results Quadriceps femoris volume of the more-affected leg increased by 9.4 % in TG . Muscle power of the more-affected , trained ( 48.2 % ) , and the less-affected , untrained limb ( 28.1 % ) increased after training . TG showed enhanced balance ( 8.9 % ) , gait performance ( 10.6 % ) , dual-task performance , executive functions ( working memory , verbal fluency tasks ) , attention , and speed of information processing . CG showed no changes . Conclusion ECC-overload flywheel resistance exercise comprising 4 min of contractile activity per week offers a powerful aid to regain muscle mass and function , and functional performance in individuals with stroke . While the current intervention improved cognitive functions , the cause-effect relationship , if any , with the concomitant neuromuscular adaptations remains to be explored . Trial registration Clinical Trials QUESTION Does progressive resistance training improve strength and activity after stroke ? Does any increase in strength carry over to activity ? DESIGN Systematic review of r and omised trials with meta- analysis . PARTICIPANTS Adults who have had a stroke . INTERVENTION Progressive resistance training compared with no intervention or placebo . OUTCOME MEASURES The primary outcome was change in strength . This measurement had to be of maximum voluntary force production and performed in muscles congruent with the muscles trained in the intervention . The secondary outcome was change in activity . This measurement had to be a direct measure of performance that produced continuous or ordinal data , or with scales that produced ordinal data . RESULTS Eleven studies involving 370 participants were included in this systematic review . The overall effect of progressive resistance training on strength was examined by pooling change scores from six studies with a mean PEDro score of 5.8 , representing medium quality . The effect size of  progressive resistance training on strength was 0.98 ( 95 % CI 0.67 to 1.29 , I2=0 % ) . The overall effect of progressive resistance training on activity was examined by pooling change scores from the same six studies . The effect size of progressive resistance training on activity was 0.42 ( 95 % CI -0.08 to 0.91 , I2=54 % ) . CONCLUSION After stroke , progressive resistance training has a large effect on strength compared with no intervention or placebo . There is uncertainty about whether these large increases in strength carry over to improvements in activity . REVIEW REGISTRATION PROSPERO CRD42015025401 . [ Dorsch S , Ada L , Alloggia D ( 2018 ) Progressive resistance training increases strength after stroke but this may not carry over to activity : a systematic review . Journal of Physiotherapy 64 : 84 - 90 ]
Conclusions : Age-related differences support the impact of stroke-related sarcopenia as a contributor to hemiparetic muscle dysfunction .
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 .