The value of strength training for older adults. Age differences in knee extension power, contractile velocity, and fatigability. The effect of lower limb muscle fatigue on obstacle negotiation during walking in older adults. The Effect of a Four-Week Balance Training Program on Anticipatory Postural Adjustments in Older Adults: A Pilot Feasibility Study. Ankle force and rate of force production increase following high intensity strength training in frail older adults Physical activity, muscle function, falls and fractures Effects of balance training on muscle coactivation during postural control in older adults: a randomized controlled trial. Efficacy of Nintendo Wii training on mechanical leg muscle function and postural balance in community-dwelling older adults: a randomized controlled trial. Effects of Aging on the Biomechanics of Slips and Falls Vitamin D supplementation improves neuromuscular function in older people who fall.
Health in older adults can best be measured in terms of functional status . Skeletal muscle strength has been reported to be a determinant of functional status in older individuals . Two major contributors to the decline in muscle function as a person ages are disuse and physical inactivity . Declining muscle function through a loss of muscular strength may decrease functional independence and mobility and increase the risk for falls and injuries , physical frailty , and disability .  Older individuals lacking an appropriate amount of muscular strength may not be able to perform various activities of daily living , which are important indicators of independence The purpose s of this study were to examine age and gender differences in knee extensor strength , power , and fatigue using open- and closed-chain testing procedures . We tested the hypothesis that specific strength ( strength/unit muscle mass ) would not differ by age , whereas age differences in specific power and fatigue would remain consequent to blunted maximal contractile velocity . Skeletal muscle performance was examined in 28 young ( 26.9 + /- 0.7 yr ) and 24 older ( 63.6 + /- 0.8 yr ) men and women . Assessment s included one-repetition maximum strength for knee extension , leg press , and squat ; concentric knee extensor peak power , velocity , and fatigability ; and  sit-to-st and power , fatigability , and relative neural activation ( electromyograph activity during sit-to-st and movement normalized to electromyograph activity during isometric maximum voluntary contraction ) . Thigh lean mass ( TLM ; kg ) was assessed by dual-energy X-ray absorptiometry . Specific strength ( N/kg TLM ) and specific power ( W/kg TLM ) were estimated by dividing absolute values by TLM . Age differences in specific strength were observed for knee extension only ( young , 41.2 + /- 1.0 N/kg TLM ; older , 32.4 + /- 1.0 N/kg TLM ; P < 0.05 ) . Adjustment for TLM did not negate age differences in knee extension specific power ( 25 - 41 % lower in older ; P < 0.05 ) across loads tested . Older adults experienced fatigue across 10 repetitions of knee extension as peak velocity fell by 24 % ( P < 0.05 ) . Deficits in concentric power persist after adjustment for TLM as maximum contractile velocity falls markedly with aging . Older adults are less capable of sustaining maximum concentric velocity during repetitive contractions . These findings suggest that velocity impairments are a possible contributor to mobility loss and falls risk among older adults . Interventions for improving contractile velocity should be pursued Tripping over obstacles is a common cause of falls in older adults , and muscle fatigue , which can alter walking patterns , may add to this risk . To date , no study has examined the effect of lower limb muscle fatigue on obstacle negotiation in older adults . 30 older adults ( 13 women , aged 78.3 [ 6.2 ] years )  negotiated a 12 m obstacle course , while completing a visual secondary task , under two r and omized conditions : rested or fatigued . For the fatigue condition , participants performed a repeated sit-to-st and movement , as fast as possible , until they could no longer continue . Participants then immediately began walking trials . Kinematic and kinetic data were collected on approach to , during , and after crossing a height-adjustable target obstacle ( 10 % and 20 % of leg length ) . Repeated measures ANOVA showed a statistically significant increase in lead limb vertical loading rate after stepping over the 10 % obstacle when fatigued , relative to rested ( P=0.046 ) . No other significant between-condition differences ( > 0.05 ) were observed for the other kinematic variables when negotiating the 10 % obstacle . Furthermore , no significant between-condition differences ( P>0.05 ) were observed for any kinetic or kinematic variables when negotiating the 20 % obstacle . This study describes a feasible method for investigating the consequences of lower limb muscle fatigue on obstacle crossing . The current finding of increased vertical loading rate when fatigued supports the need for further investigation into the effect of muscle fatigue on gait under different environmental conditions , fatiguing a range of muscles , analyzing a more comprehensive array of kinetic and kinematic measures , and in healthy and clinical population BACKGROUND Balance deterioration in older adults limits their activities of daily living , community participation , and is a significant risk factor for falls . One contributory element to this functional decline is impairment of anticipatory postural adjustments ( APAs ) . OBJECTIVES To evaluate the role and feasibility of a novel training program in improving APAs for balance control of older adults . METHOD Six older adults ( 73.3±5.0 years ) were r and omly assigned into the Experimental ( EG ) and Control groups ( CG ) . The EG participated in four weeks of APA-focused training involving catching a medicine ball while st and ing . All subjects were exposed to predictable external and self-initiated perturbations before and after training . EMG activity of eight trunk and leg muscles was recorded bilaterally and muscle onsets were analyzed during the anticipatory phase of postural control . Clinical tests of balance ( Timed-Up and Go , Single limb stance , and Activities-specific Balance Confidence scale ) were implemented . RESULTS Early onsets of APA activity prior to the external perturbations were seen in the EG following training . Moreover , early APA activity was observed in the EG prior to bilateral arm flexion , a task that was not a part of training , indicating a transfer of the learning effect of training . The improvement of APAs in the EG also result ed in improved performance on clinical outcome measures . There were no improvements seen in the CG for both the APA activity and the clinical balance tests . CONCLUSION The study outcome suggests that a four-week APA-based training program is feasible and could be effective in improving postural control , functional balance , mobility , and quality of life in older adults 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 Study design A thematic review . Objectives To evaluate if physical activity enhances muscle strength , improves balance , and reduces the fall frequency and the fracture incidence .  Background One of the major medical problems of today is the increasing incidence of fragility fractures .  Muscle strength and fall is one of the major determinants of a fracture . If physical activity could increase muscle strength , improve balance and reduce the fall frequency , then training could be recommended as prevention for fractures . Methods The review used Medline ( Pub Med ) and the search words exercise , physical activity , muscle strength , balance , falls , fractures . R and omized controlled trials ( RCT ) were predominantly included , although this not is a systematic review . Results The evidence that physical activity modifies the risk factors for fall is compelling , although RCT with fractures as end point are lacking . Physical activity is associated with improved muscle strength , co-ordination and balance .  Physical training increases muscle strength also in octogenarians by up to 200 % , i.e. a much more pronounced effect than the corresponding increase in muscle volume or bone mass . There is also evidence that physical activity decreases the actual number of falls . Observational cohort and case-control studies imply that physical activity is associated with reduced hip fracture risk . If exercise reduces the number of vertebral fractures and other fragility fractures are less evaluated . Conclusions Physical activity in older ages can be recommended to improve muscle strength and balance , to reduce the risk to fall and fractures , although the highest level of evidence – RCT with fracture as endpoint – is lacking BACKGROUND Recently , several studies have reported age-associated increases in muscle coactivation during postural control . A rigid posture induced by strong muscle coactivation reduces the degree of freedom to be organized by the postural control system . The purpose of this study was to clarify the effect of balance training on muscle coactivation during postural control in older adults . METHODS Forty-eight subjects were r and omized into an intervention ( mean age : 81.0 ± 6.9 years ) and a control group ( mean age : 81.6 ± 6.4 years ) . The control group did not receive any intervention . Postural control ability ( postural sway during quiet st and ing , functional reach , and functional stability boundary ) was assessed before and after the intervention . A cocontraction index was measured during the postural control tasks to assess muscle coactivation . RESULTS Cocontraction index values in the intervention group significantly decreased following the intervention phase for functional reach ( p < .0125 ) . Cocontraction index values had a tendency to decrease during functional stability boundary for forward and quiet st and ing tasks . Functional improvements were observed in some of the tasks after the intervention , that is , functional reach , functional stability boundary for forward , one-leg stance , and timed up and go ( p < .05 ) . CONCLUSIONS Our study raised the possibility that balance training for older adults was associated with decreases in muscle coactivation during postural control . Postural control exercise could potentially lead older adults to develop more efficient postural control strategies without increasing muscle coactivation . Further research is needed to clarify in greater detail the effects of changes in muscle coactivation BACKGROUND Older adults show increased risk of falling and major risk factors include impaired lower extremity muscle strength and postural balance . However , the potential positive effect of biofeedback-based Nintendo Wii training on muscle strength and postural balance in older adults is unknown . METHODS This r and omized controlled trial examined postural balance and muscle strength in community-dwelling older adults ( 75±6 years ) pre- and post-10 weeks of biofeedback-based Nintendo Wii training ( WII , n = 28 ) or daily use of ethylene vinyl acetate copolymer insoles ( controls [ CON ] , n = 30 ) . Primary end points were maximal muscle strength ( maximal voluntary contraction ) and center of pressure velocity moment during bilateral static stance . RESULTS Intention-to-treat analysis with adjustment for age , sex , and baseline level showed that the WII group had higher maximal voluntary contraction strength ( 18 % ) than the control group at follow up ( between-group difference = 269 N , 95 % CI = 122 ; 416 , and p = .001 ) . In contrast , the center of pressure velocity moment did not differ ( 1 % ) between WII and CON at follow-up ( between-group difference = 0.23 mm(2)/s , 95 % CI = -4.1 ; 4.6 , and p = .92 ) . For secondary end points , pre-to-post changes favoring the WII group were evident in the rate of force development ( p = .03 ) , Timed Up and Go test ( p = .01 ) , short Falls Efficacy Scale-International ( p = .03 ) , and 30-second repeated Chair St and Test ( p = .01 ) . Finally , participants rated the Wii training highly motivating at 5 and 10 weeks into the intervention . CONCLUSIONS Biofeedback-based Wii training led to marked improvements in maximal leg muscle strength ( maximal voluntary contraction ; rate of force development ) and overall functional performance in community-dwelling older adults . Unexpectedly , static bilateral postural balance remained unaltered with Wii training . The high level of participant motivation suggests that biofeedback-based Wii exercise may ensure a high degree of compliance to home- and /or community-based training in community-dwelling older adults Although much has been learned in recent decades about the deterioration of muscular strength , gait adaptations , and sensory degradation among older adults , little is known about how these intrinsic changes affect biomechanical parameters associated with slip-induced fall accidents . In general , the objective of this laboratory study was to investigate the process of initiation , detection , and recovery of inadvertent slips and falls . We examined the initiation of and recovery from foot slips among three age groups utilizing biomechanical parameters , muscle strength , and sensory measurements . Forty-two young , middle-age , and older participants walked around a walking track at a comfortable pace . Slippery floor surfaces were placed on the track over force platforms at r and om intervals without the participants ' awareness . Results indicated that younger participants slipped as often as the older participants , suggesting that the likelihood of slip initiation is similar across all age groups ; however , older individuals ? recovery process was much slower and less effective . The ability to successfully recover from a slip ( thus preventing a fall ) is believed to be affected by lower extremity muscle strength and sensory degradation among older individuals . Results from this research can help pinpoint possible intervention strategies for improving dynamic equilibrium among older adults BACKGROUND vitamin D supplementation reduces the incidence of fractures in older adults . This may be partly mediated by effects of vitamin D on neuromuscular function . OBJECTIVE to determine the effects of vitamin D supplementation on aspects of neuromuscular function known to be risk factors for falls and fractures . DESIGN r and omised , double-blind , placebo-controlled study . SETTING falls clinic taking referrals from general practitioners and accident and emergency department . SUBJECTS 139 ambulatory subjects ( > /=65 years ) with a history of falls and 25-hydroxyvitamin D ( 25OHD ) < /=12 microg/l . INTERVENTION patients were r and omised to receive a single intramuscular injection of 600,000 i.u . ergocalciferol or placebo . OUTCOME MEASURES assessment s including biochemistry , postural sway , choice reaction time ( CRT ) , aggregate functional performance time ( AFPT ) , and quadriceps strength were carried out at baseline and 6 months post-intervention . RESULTS baseline characteristics were comparable between both groups . 25OHD in the treatment group increased significantly at 6 months . AFPT deteriorated in the control group and improved in the intervention group , representing a significant difference between groups ( + 6.6 s versus -2.0 s , t = 2.80 , P < 0.05 ) . Similar changes were observed for CRT ( -0.06 s versus + 0.41 s , t = -2.52 , P < 0.01 ) and postural sway ( + 0.0025 versus -0.0138 , t = 2.35 , P < 0.02 ) . There was no significant difference in muscle strength change between groups ( -10 N versus -2 N , t = -1.26 , ns ) . A significant correlation between change in AFPT and change in 25OHD levels was observed ( r = 0.19 , P = 0.03 ) . There was no significant difference in the number of falls ( 0.39 versus 0.24 , t = 1.08 , P = 0.28 ) or fallers ( 14 versus 11 , P = 0.52 ) between two groups . CONCLUSIONS vitamin D supplementation , in fallers with vitamin D insufficiency , has a significant beneficial effect on functional performance , reaction time and balance , but not muscle strength . This suggests that vitamin D supplementation improves neuromuscular or neuroprotective function , which may in part explain the mechanism whereby vitamin D reduces falls and fractures
CONCLUSION On the basis of systematic review of relevant literature , it appears that muscle fatigue induces clear deteriorations in reactive postural control .
BACKGROUND Falls are the leading cause of traumatic brain injury and fractures and the No. 1 cause of emergency department visits by older adults .
Although declines in muscle strength and sensory function contribute to increased falls in older adults , skeletal muscle fatigue is often overlooked as an additional contributor to fall risk .
In an effort to increase awareness of the detrimental effects of skeletal muscle fatigue on postural control , we sought to systematic ally review research studies examining this issue .
PURPOSE The specific purpose of this review was to provide a detailed assessment of how anticipatory and reactive postural control tasks are influenced by  acute muscle fatigue in healthy older individuals .