Muscle strength and rising from a chair in older adults

Age-related modifications of muscle synergies during daily-living tasks: A scoping review

BACKGROUND

Aging is associated with changes in neuromuscular control that can lead to difficulties in performing daily living tasks. Muscle synergy analysis allows the assessment of neuromuscular control strategies and functional deficits. However, the age-related changes of muscle synergies during functional tasks are scattered throughout the literature. This review aimed to synthesize the existing literature on muscle synergies in elderly people during daily-living tasks and examine how they differ from those exhibited by young adults.

METHODS

The Medline, CINAHL and Web of Science databases were searched. Studies were included if they focused on muscle synergies in elderly people during walking, sit-to-stand or stair ascent, and if muscle synergies were obtained by a matrix factorization algorithm.

FINDINGS

Seventeen studies were included after the screening process. The muscle synergies of 295 elderly people and 182 young adults were reported, including 5 to 16 muscles per leg, or leg and trunk. Results suggest that: 1) elderly people and young adults retain similar muscle synergies' number, 2) elderly people have higher muscles weighting during walking, and 3) an increased inter and intra-subject temporal activation variability during specific tasks (i.e., walking and stair ascent, respectively) was reported in elderly people compared to young adults.

INTERPRETATION

This review gives a comprehensive understanding of age-related changes in neuromuscular control during daily living tasks. Our findings suggested that although the number of synergies remains similar, metrics such as spatial and temporal structures of synergies are more suitable to identify neuromuscular control deficits between young adults and elderly people.

Rollator usage lets young individuals switch movement strategies in sit-to-stand and stand-to-sit tasks

The transitions between sitting and standing have a high physical and coordination demand, frequently causing falls in older individuals. Rollators, or four-wheeled walkers, are often prescribed to reduce lower-limb load and to improve balance but have been found a fall risk. This study investigated how rollator support affects sit-to-stand and stand-to-sit movements. Twenty young participants stood up and sat down under three handle support conditions (unassisted, light touch, and full support). As increasing task demands may affect coordination, a challenging floor condition (balance pads) was included. Full-body kinematics and ground reaction forces were recorded, reduced in dimensionality by principal component analyses, and clustered by k-means into movement strategies. Rollator support caused the participants to switch strategies, especially when their balance was challenged, but did not lead to support-specific strategies, i.e., clusters that only comprise light touch or full support trials. Three strategies for sit-to-stand were found: forward leaning, hybrid, and vertical rise; two in the challenging condition (exaggerated forward and forward leaning). For stand-to-sit, three strategies were found: backward lowering, hybrid, and vertical lowering; two in the challenging condition (exaggerated forward and forward leaning). Hence, young individuals adjust their strategy selection to different conditions. Future studies may apply this methodology to older individuals to recommend safe strategies and ultimately reduce falls.

Comparison of toe pressure strength in the standing position and toe grip strength in association with the presence of assistance in standing up: a cross-sectional study in community-dwelling older adults

PURPOSE

We believe that toe pressure strength in the standing position, which is closer to the actual movement, is more associated with standing up in the older adults than the conventional toe grip strength. Therefore, the purpose of this study is to examine the association between toe pressure strength in the standing position and the presence of assistance in standing up in the older adults.

METHODS

Ninety-five community-dwelling older adults (82 ± 8 years old, 72% female) were included in this study. The patients were evaluated based on their need for assistance in standing up. Physical functions, including toe pressure strength in the standing position, toe grip strength, hand grip strength, knee extension strength, one-leg standing time with eyes open, and maximal walking speed, were measured.

RESULTS

When compared with and without assistance to stand up, the group requiring assistance had weaker toe pressure strength in the standing position than the group without assistance (p = 0.015, ES = 0.53). After adjusting for confounding factors, the final model revealed that toe pressure strength in the standing position was associated with the use of assistance in standing up (odds ratio 0.94 [0.88-0.99, p = 0.025]).

CONCLUSION

Toe pressure strength in the standing position was associated with the use of assistance in standing up in older adults. Improving toe pressure strength in the standing position may facilitate the ability of older adults to stand up.

Standing Up from a Chair with an Asymmetrical Initial Foot Position Decreases Trunk and Masticatory Muscle Activities in Healthy Young Men

This study aimed to identify the activation of lower extremity, trunk, and masticatory muscle and trunk kinematics of the initial foot position during the sit-to-stand (STS) movement. Sixteen young men participated in this cross-sectional pilot study and performed STS using both symmetrical and asymmetrical foot positions. Activation of the tibialis anterior (TA), gastrocnemius lateral head (GA), rectus femoris (RF), biceps femoris (BF), rectus abdominis, erector spinae (ES), sternocleidomastoid (SCM), upper trapezius (UT), temporalis (TE), and masseter muscles in the dominant side was determined. For trunk kinematics, head and trunk velocities, front-back (For-Back) and mediolateral (Med-Lat) weight translation rates, and trunk inclination were measured. GA, TA, BF, and RF activation significantly increased, whereas ES, SCM, UT, and TE activation significantly decreased when using the asymmetrical foot position. Head velocity, For-Back, Med-Lat, and trunk inclination were also significantly decreased. In conclusion, the asymmetrical foot position increases muscle activation in the lower extremities and decreases trunk inclination. In addition, ES, UT, and TE muscle activity decreases at the initial asymmetrical foot position.

What are the effects of simulated muscle weakness on the sit-to-stand transfer?

Populations with lower extremity muscle weakness have difficulty performing the sit-to-stand (STS) transfer. The degree of weakness that can be tolerated before compromising the ability to perform this task is unknown. Using dynamic simulations, we investigated the effects of weakness before changes in kinematics/kinetics would be required. Lower extremity muscles were weakened globally and individually and muscle forces were re-estimated as the model tracked original task kinematics/kinetics. The STS transfer was sensitive to quadriceps and plantarflexor weakness, suggesting that strengthening these muscles or changing kinematics are essential for populations who have difficulty rising from a chair independently.

The Association Between Femoral Neck-Shaft Angle and Aging and Its Influence on the Performance of Functional Activity: A Cross-Sectional Investigation

The purposes of this study were first to examine the association between aging and both the magnitude and asymmetry in the femoral neck-shaft angle (NSA). The second purpose was to determine the effects of both the magnitude and NSA asymmetry on the performance of functional activities in healthy individuals. Fifty-one subjects participated in this study. The femoral NSA was measured on computed tomography scout images. The participants performed four performance tests. Four hierarchical regression models were constructed to explore the effect of each predictor on the outcomes. Aging was associated with NSA asymmetry, but not with the degree of NSA. Age contributed significantly to the variability of all functional performance tests except the 10-m walking speed. The degree of the NSA did not contribute to the prediction of the functional performance tests. However, asymmetry in the NSA added significantly to the prediction of all functional performance tests except the 10-m walking speed.

Exercise Snacking to Improve Muscle Function in Healthy Older Adults: A Pilot Study

Loss of muscle mass and strength are seemingly accepted as part of the ageing process, despite ultimately leading to the loss of independence. Resistance exercise is considered to be primary defence against loss of muscle function in older age, but it typically requires access to exercise equipment often in a gym environment. This pilot study aimed at examining the effect of a 28-day, unsupervised home-based exercise intervention on indices of leg strength and muscle size in healthy older adults. Twenty participants were randomly assigned to either maintain their habitual physical activity levels (Control; n=10; age, 74 (5) years; body mass, 26.3 (3.5) kg/m²) or undertake "exercise snacks" twice daily (ES; n=10; age, 70 (4) years; body mass, 25.0 (3.4) kg/m²). Both groups consumed 150 g of yogurt at their breakfast meal for the duration of the intervention. Sixty-second sit-to-stand score improved by 31% in ES, with no change in Control (p < 0.01). Large effect sizes were observed for the difference in change scores between the groups for interpolated maximum leg pressing power (6% increase in ES) and thigh muscle cross-sectional area (2% increase in ES). The present pilot data suggest that exercise snacking might be a promising strategy to improve leg muscle function and size in older adults and that further investigation into zero-cost exercise strategies that allow high frequency of training is warranted.

Older Adults with Weaker Muscle Strength Stand up from a Sitting Position with More Dynamic Trunk Use

The ability to stand up from a sitting position is essential for older adults to live independently. Body-fixed inertial sensors may provide an approach for quantifying the sit-to-stand (STS) in clinical settings. The aim of this study was to determine whether measurements of STS movements using body-fixed sensors yield parameters that are informative regarding changes in STS performance in older adults with reduced muscle strength. In twenty-seven healthy older adults, handgrip strength was assessed as a proxy for overall muscle strength. Subjects were asked to stand up from a chair placed at three heights. Trunk movements were measured using an inertial sensor fixed to the back. Duration, angular range, and maximum angular velocity of STS phases, as well as the vertical velocity of the extension phase, were calculated. Backwards elimination using Generalized Estimating Equations was used to determine if handgrip strength predicted the STS durations and trunk kinematics. Weaker subjects (i.e., with lower handgrip strength) were slower during the STS and showed a larger flexion angular range and a larger extension angular range. In addition, weaker subjects showed a greater maximum angular velocity, which increased with lower seat heights. Measurements with a single inertial sensor did reveal that older adults with lower handgrip strength employed a different strategy to stand up from a sitting position, involving more dynamic use of the trunk. This effect was greatest when elevating body mass. Trunk kinematic parameters were more sensitive to reduced muscle strength than durations.

Physical function and muscle strength in sporadic inclusion body myositis

INTRODUCTION

In this study, self-reported physical function, functional capacity, and isolated muscle function were investigated in sporadic inclusion body myositis (sIBM) patients.

METHODS

The 36-item Short Form (SF-36) Health Survey and 2-min walk test (2MWT), timed up & go test (TUG), and 30-s chair stand performance were evaluated. In addition, patients were tested for knee extensor muscle strength (isokinetic dynamometer) and leg extension power (Nottingham power rig).

RESULTS

TUG performance was the strongest predictor of self-reported physical function (r² = 0.56, P < 0.05). Knee extension strength and between-limb strength asymmetry were the strongest multi-regression indicators of TUG performance (r² = 0.51, P < 0.05). Strength asymmetry showed the strongest single-factor (negative) association with 2MWT performance (r² = 0.49, P < 0.05).

DISCUSSION

TUG assessment appears to sensitively predict self-perceived physical function in sIBM patients. Notably, between-limb asymmetry in lower limb muscle strength had a substantial negative impact on motor tasks involving gait function. Muscle Nerve 56: E50-E58, 2017.

Scottish Country Dance: Benefits to Functional Ability in Older Women

The effects of long-term participation in Scottish country dance on body composition, functional ability, and balance in healthy older females were examined. Participants were grouped into dancers and physically active nondancers (ages 60–70 and 70–80 for both groups). Physical activity, body composition (body-mass index, skinfold thickness, waist-to-hip ratio), functional ability (6-min walk distance, 6-m walk time, 8-ft up-and-go time, lower body flexibility, shoulder flexibility), and static balance were measured. Younger dancers and physically active nondancers had similar 6-min walk distance, 6-m walk time, and 8-ft up-and-go time results; however, while older dancers performed similarly to younger dancers, older physically active nondancers performed poorer than their younger counterparts (p< .05). Body composition and static balance were the same for all groups. Regular physical activity can maintain body composition and postural stability with advancing age; however, Scottish country dance can delay the effects of aging on locomotion-related functional abilities.

Not all is lost: old adults retain flexibility in motor behaviour during sit-to-stand

Sit-to-stand is a fundamental activity of daily living, which becomes increasingly difficult with advancing age. Due to severe loss of leg strength old adults are required to change the way they rise from a chair and maintain stability. Here we examine whether old compared to young adults differently prioritize task-important performance variables and whether there are age-related differences in the use of available motor flexibility. We applied the uncontrolled manifold analysis to decompose trial-to-trial variability in joint kinematics into variability that stabilizes and destabilizes task-important performance variables. Comparing the amount of variability stabilizing and destabilizing task-important variables enabled us to identify the variable of primary importance for the task. We measured maximal isometric voluntary force of three muscle groups in the right leg. Independent of age and muscle strength, old and young adults similarly prioritized stability of the ground reaction force vector during sit-to-stand. Old compared to young adults employed greater motor flexibility, stabilizing ground reaction forces during sit-to-sand. We concluded that freeing those degrees of freedom that stabilize task-important variables is a strategy used by the aging neuromuscular system to compensate for strength deficits.

The effects of symmetric and asymmetric foot placements on sit-to-stand joint moments

The purpose of this study was to determine the effects of symmetric and asymmetric foot placements on joint moments during sit-to-stand movements. Three symmetric (foot-neutral, foot-back, and foot-intermediate) and three asymmetric foot placements (preferred stagger, nonpreferred stagger, and intermediate stagger) were tested. Standard (46 cm) and low (41 cm) seat heights were chosen to represent an average public seat height and a 10% lower seat height. Using inverse dynamics, maximum ankle plantarflexion, knee extension, hip extension, and hip abduction moments were calculated. Hip extension moments were significantly increased when using foot-neutral as compared to foot-back. Ankle plantarflexion and knee extension moments were significantly increased when a foot was placed in the posterior position as compared to the anterior position for preferred and nonpreferred stagger. Knee extension moments were significantly increased at the low seat height as compared to the standard seat height. When shifting the feet anterior or posterior for symmetric placements during sit-to-stand, the most dramatic effect was an increase in hip extension moments when the feet are shifted anteriorly. Utilizing asymmetric foot placements during sit-to-stand produced increases in ankle plantarflexion and knee extension moments for the posteriorly placed limb, with reductions in the anteriorly placed limb.

One-repetition maximum strength test represents a valid means to assess leg strength in vivo in humans

Skeletal muscle strength is often determined to evaluate the adaptive response to an exercise intervention programme. Although dynamometry is considered the "gold standard" for the assessment of muscle strength in vivo, one-repetition maximum (1-RM) testing performed on training-specific equipment is more commonly applied. We assessed the validity of specific knee extension 1-RM testing by comparison with dynamometry in a heterogeneous population (n=55). All participants performed 1-RM tests on regular leg extension and leg press machines. Additionally, isometric (at seven different knee angles) and isokinetic (at four different velocities) knee extension peak torques were determined. Pearson's r was calculated for the relationship between 1-RM data and peak torques for the entire population and for subgroups defined by age and gender. One-repetition maximum strength correlated strongly with the dynamometer results. One-repetition maximum leg extension correlated more strongly with peak torques than did 1-RM leg press (0.78<or=r<or=0.88 vs. 0.72<or=r<or=0.77; P<0.001). Similar correlations were observed in all subgroups. We conclude that 1-RM testing represents a valid means to assess leg muscle strength in vivo in young and elderly men and women. Considering the importance of training specificity in strength assessment, we argue that 1-RM testing can be applied to assess changes in leg muscle strength following an exercise intervention.

Reliability of performance-based measures in people awaiting joint replacement surgery of the hip or knee

BACKGROUND AND PURPOSE

Understanding the reliability of selected measurement tools is a prerequisite to understanding the effects of clinical interventions. The aim of this investigation was to determine the reliability of the 50-Foot Timed Walk (50 FTW) and 30-second Chair Stand Test (30 CST) in subjects awaiting joint replacement surgery of the hip or knee.

METHODS

Eighty-two subjects participating in a 6-week exercise programme were assessed at baseline, 7 weeks and 15 weeks. Four trials of the 50 FTW and two trials of the 30 CST were completed at each assessment. Eleven trained assessors completed the assessments.

RESULTS

Intra-class correlations were consistently high for the 50 FTW and 30 CST at all assessments. At the baseline assessment, trial 1 was found to be significantly different from subsequent trials for both the 50 FTW and 30 CST. This effect was not evident at the 7-week and 15-week assessments. At the baseline assessment, scores for the 50 FTW became stable after the first trial. Estimates of minimum detectable change indicated that participants needed to change by more than 3.08 seconds and 1.64 stands to be 90% confident that a real change had occurred for the 50 FTW and 30 CST, respectively.

CONCLUSION

The 50 FTW and 30 CST can be reliable measures of physical performance. However, because we found a practice effect at the baseline assessment, a practice trial should be allowed before data collection begins. Because only two trials of the 30 CST were completed, further research is required to confirm whether scores at the initial assessment become stable on repeated testing.

The effect of beta-alanine supplementation on neuromuscular fatigue in elderly (55-92 Years): a double-blind randomized study

BACKGROUND

Ageing is associated with a significant reduction in skeletal muscle carnosine which has been linked with a reduction in the buffering capacity of muscle and in theory, may increase the rate of fatigue during exercise. Supplementing beta-alanine has been shown to significantly increase skeletal muscle carnosine. The purpose of this study, therefore, was to examine the effects of ninety days of beta-alanine supplementation on the physical working capacity at the fatigue threshold (PWCFT) in elderly men and women.

METHODS

Using a double-blind placebo controlled design, twenty-six men (n = 9) and women (n = 17) (age +/- SD = 72.8 +/- 11.1 yrs) were randomly assigned to either beta-alanine (BA: 800 mg x 3 per day; n = 12; CarnoSyntrade mark) or Placebo (PL; n = 14) group. Before (pre) and after (post) the supplementation period, participants performed a discontinuous cycle ergometry test to determine the PWCFT.

RESULTS

Significant increases in PWCFT (28.6%) from pre- to post-supplementation were found for the BA treatment group (p < 0.05), but no change was observed with PL treatment. These findings suggest that ninety days of BA supplementation may increase physical working capacity by delaying the onset of neuromuscular fatigue in elderly men and women.

CONCLUSION

We suggest that BA supplementation, by improving intracellular pH control, improves muscle endurance in the elderly. This, we believe, could have importance in the prevention of falls, and the maintenance of health and independent living in elderly men and women.

Cross-sectional relationship between physical fitness components and functional performance in older persons living in long-term care facilities

Background

The age-related deterioration of physiological capacities such as muscle strength and balance is associated with increased dependence. Understanding the contribution of physical fitness components to functional performance facilitates the development of adequate exercise interventions aiming at preservation of function and independence of older people. The aim of the study was to investigate the relationship between physical fitness components and functional performance in older people living in long-term care facilities.

Methods

Design cross-sectional study

Subjects 226 persons living in long-term care facilities (mean age: 81.6 ± 5.6).

Outcome measures Physical fitness and functional performance were measured by performance-based tests.

Results

Knee and elbow extension strength were significantly higher in men (difference = 44.5 and 50.0 N, respectively), whereas women were more flexible (difference sit & reach test = 7.2 cm). Functional performance was not significantly different between the genders. In men, motor coordination (eye-hand coordination) and measures of strength were the main contributors to functional performance, whereas in women flexibility (sit and reach test) and motor coordination (tandem stance and eye-hand coordination) played a major role.

Conclusion

The results of this study show that besides muscle strength, fitness components such as coordination and flexibility are associated with functional performance of older people living in long-term care facilities.

This suggests that men and women living in long-term care facilities, differ considerably concerning the fitness factors contributing to functional performance. Women and men may, therefore, need exercise programs emphasizing different fitness aspects in order to improve functional performance.

Force Steadiness in the Lower Extremities as an Independent Predictor of Functional Performance in Older Women

The relationship between isometric force control and functional performance is unknown. Submaximal steadiness and accuracy were measured during a constant force-matching task at 50% of maximal isometric voluntary contraction (MVC) of the knee extensors in 19 older women (70–89 years). Other variables included MVC, rate of torque development, and EMG activity. Functional performance was assessed during maximal performance of walking endurance, chair rising, and stair climbing. Isometric steadiness (but not accuracy) was found to independently predict chair-rise time and stair-climbing power and explained more variance in these tasks than any other variable. Walking endurance was related to muscle strength but not steadiness. These results suggest that steadiness is an independent predictor of brief, stressful functional-performance tasks in older women with mild functional impairment. Thus, improving steadiness might help reduce functional limitations or disability in older adults.

Knee extensor isometric unsteadiness does not predict functional limitation in older adults

OBJECTIVE

To determine how knee extensor steadiness is related to age and difficulty performing everyday tasks.

DESIGN

In this cross-sectional study performed at a research laboratory, 50 older adults (age range, (56-95 yrs) performed steadiness testing at 50% of maximum strength and were timed and rated on four tasks of daily living: chair rise, stair ascent and descent, and walk. The independent variables of age, steadiness, and strength-to-weight ratio were entered into regression models with the ratings and time to complete the four everyday tasks as dependent variables.

RESULTS

The strength-to-weight ratio was the only significant predictor in the multiple regression models, explaining 29%, 33%, 14%, and 14% of the variance in gait speed and time to complete a chair rise, stair ascent, and stair descent, respectively. Similar results were seen with task ratings. Age was not correlated with steadiness (r = 0.25, P = 0.07).

CONCLUSION

This study suggests that knee extensor isometric steadiness performance does not carry over to tasks of everyday living, and older subjects, regardless of age, have similar steadiness values. Because the strength-to-weight ratio predicted the most variance in functional performance, it is recommended that muscle strength be improved to increase function in older adults.

Association between subject functional status, seat height, and movement strategy in sit-to-stand performance

OBJECTIVES

To explore the association between an individual's functional status, movement task difficulty, and effectiveness of compensatory movement strategies within a sit-to-stand (STS) paradigm.

DESIGN

Cross-sectional study.

SETTINGS

Rehabilitation unit of the Istituto Nazionale Riposo e Cura Anziani Geriatric Hospital of Florence, Italy.

PARTICIPANTS

A convenience sample (131 subjects) of the outpatient clinic and day-hospital population.

MEASUREMENTS

A performance-based test (repeated chair standing) was used to divide the subjects into five functional groups. Subjects performed a series of single STS tasks across a range of five descending seat heights. They were instructed to stand without using arms or compensatory strategies. If unable, swinging the arms was allowed, and if the inability persisted, subjects could push with their arms during subsequent attempts. The strategy or inability to stand formed the dependent measures.

RESULTS

Subjects within the two highest functional groups could complete the single STS task at all seat heights, with a slight increased use of compensatory strategies at the lowest seat height. The effectiveness of the compensatory strategies decreased rapidly as a function of seat height and functional status. One-third (35.5%) of the subjects in the middle functional group swung their arms at the lower seat heights. Across the three least functional groups, 11.8%, 30.6%, and 83.3% of the subjects, respectively, were unable to stand at the lowest seat height.

CONCLUSION

The individual's functional status and difficulty of the task influenced the effectiveness of a compensatory strategy to maintain the ability to stand, supporting the idea that disability depends on the interplay between environmental demands and physical ability.

Determinants of the Sit-to-Stand Movement: A Review

Background and Purpose. The sit-to-stand (STS) movement is a skill that helps determine the functional level of a person. Assessment of the STS movement has been done using quantitative and semiquantitative techniques. The purposes of this study were to identify the determinants of the STS movement and to describe their influence on the performance of the STS movement. Methods. A search was made using MEDLINE (1980–2001) and the Science Citation Index Expanded of the Institute for Scientific Information (1988–2001) using the key words “chair,” “mobility,” “rising,” “sit-to-stand,” and “standing.” Relevant references such as textbooks, presentations, and reports also were included. Of the 160 identified studies, only those in which the determinants of STS movement performance were examined using an experimental setup (n=39) were included in this review. Results. The literature indicates that chair seat height, use of armrests, and foot position have a major influence on the ability to do an STS movement. Using a higher chair seat resulted in lower moments at knee level (up to 60%) and hip level (up to 50%); lowering the chair seat increased the need for momentum generation or repositioning of the feet to lower the needed moments. Using the armrests lowered the moments needed at the hip by 50%, probably without influencing the range of motion of the joints. Repositioning of feet influenced the strategy of the STS movement, enabling lower maximum mean extension moments at the hip (148.8 N·m versus 32.7 N·m when the foot position changed from anterior to posterior). Discussion and Conclusion. The ability to do an STS movement, according to the research reviewed, is strongly influenced by the height of the chair seat, use of armrests, and foot position. More study of the interaction among the different determinants is needed. Failing to account for these variables may lead to erroneous measurements of changes in STS performance.

Reliability and comparison of weight-bearing ability during standing tasks for individuals with chronic stroke

OBJECTIVES

To determine the test-retest reliability over 2 separate days for weight-bearing ability during standing tasks in individuals with chronic stroke and to compare the weight-bearing ability among 5 standing tasks for the paretic and nonparetic limbs.

DESIGN

Prospective study using a convenient sample.

SETTING

Free-standing tertiary rehabilitation center.

PARTICIPANTS

Fifteen community-dwelling stroke individuals with moderate motor deficits; volunteer sample.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Weight-bearing ability as measured by the vertical ground reaction force during 5 standing tasks (rising from a chair, quiet standing, weight-shifting forward, backward, laterally).

RESULTS

The weight-bearing ability was less for the paretic limb compared with the nonparetic limb, but the intraclass correlation coefficients were high (.95-.99) for both limbs between the 2 sessions for all 5 tasks. The forward weight-shifting ability was particularly low in magnitude on the paretic side compared with the other weight-shifting tasks. In addition, the forward weight-shift ability of the nonparetic limb was also impaired but to a lesser extent. Large asymmetry was evident when rising from a chair, with the paretic limb bearing a mean 296N and the nonparetic side bearing a mean 458N. The weight-bearing ability during all 5 tasks correlated with one another (r range,.56-.94).

CONCLUSIONS

Weight-bearing ability can be reliably measured and may serve as a useful outcome measure in individuals with stroke. We suggest that impairments of the hemiparetic side during forward weight shifting and sit-to-stand tasks presents a challenge to the motor systems of individuals with stroke, which may account for the poor balance that is often observed in these individuals.

Creatine supplementation improves muscular performance in older men

PURPOSE

Creatine supplementation has been shown to enhance muscle strength and power after only 5-7 d in young adults. Creatine supplementation could therefore benefit older individuals because aging is associated with a decrease in muscle strength and explosive power.

METHODS

We examined the effects of 7 d of creatine supplementation in normally active older men (59-72 yr) by using a double-blind, placebo-controlled design with repeated measures. After a 3-wk familiarization period to minimize learning effects, a battery of tests was completed on three occasions separated by 7 d (T1, T2, and T3). After T1, subjects were matched and randomly assigned into creatine (N = 10) and placebo (N = 8) groups. After T2, subjects consumed supplements (0.3 g x kg(-1) x d(-1)) for 7 d until T3. All subjects were tested for maximal dynamic strength (one-repetition maximum leg press and bench press), maximal isometric strength (knee extension/flexion), upper- and lower-body explosive power (6 x 10-s sprints on a cycle ergometer), and lower-extremity functional ability (timed sit-stand test and tandem gait test). Body composition was assessed via hydrostatic weighing, and blood samples were obtained to assess renal and hepatic responses and muscle creatine concentrations.

RESULTS

No significant increases in any performance measures were observed from T1 to T2 with the exception of isometric right-knee flexion in the placebo group indicating stability in the testing protocols. Significant group-by -time interactions indicated the responses from T2 to T3 were significantly greater (P <or= 0.05) in the creatine compared with the placebo group, respectively, for body mass (1.86 and -1.01 kg), fat-free mass (2.22 and 0.00 kg), maximal dynamic strength (7-8 and 1-2%), maximal isometric strength (9-15 and -6 to 1%), lower-body mean power (11 and 0%), and lower-extremity functional capacity (6-9 and 1-2%). No adverse side effects were observed.

CONCLUSION

These data indicate that 7 d of creatine supplementation is effective at increasing several indices of muscle performance, including functional tests in older men without adverse side effects. Creatine supplementation may be a useful therapeutic strategy for older adults to attenuate loss in muscle strength and performance of functional living tasks.

The Montreal rehabilitation performance profile: a task-analysis approach to quantify stair descent performance in children with intellectual disability

OBJECTIVE

To develop a clinical tool to quantify stair descent performance in children with moderate to severe intellectual disability.

DESIGN

Item identification, measurement construction, and basic testing of reliability.

SETTING

School for children with intellectual disability.

PARTICIPANTS

A sample of convenience; 18 children (age range, 5-9 yr) with moderate to severe intellectual disability, but who were ambulatory.

INTERVENTION

The Montreal Rehabilitation Performance Profile (MRPP) measurement tool, which has 4 perceptual-motor elements: movement form, time requirement, proprioceptive cues, and external cues.

MAIN OUTCOME MEASURE

Identification of perceptual-motor elements that underlie skilled stair descent and that are directly quantified from standard video recording.

RESULTS

Interrater reliability measured by percentage agreement (kappa statistic) was high for 3 elements (80%-100%; kappa =.63) and good for the fourth (67%; kappa =.52). The 4 MRPP elements are plotted on cartesian axes to yield (1) the magnitude of the contribution of each independent element to total performance outcome, and (2) a global measurement of level of functional skill, the Performance Composite Score (PCS).

CONCLUSIONS

The MRPP, and associated PCS, provide a valid measure of functional stair descent skill that does not rely on cognitive understanding of the process. This tool could be adapted to measure functional capacity in other clinical populations, including geriatric clients.

Biomechanical analysis of effects of foot placement with varying chair height on the motion of standing up

Individual experience reveals that posterior foot placement enables one to stand up easily from a chair. However, the way in which foot placement affects this motion has not been investigated in detail. This study was performed to examine the effects of foot placement in the initial stage of the dynamics of standing up from a chair. Subjects wearing light-emitting diode markers and surface electrodes stood up from a chair over force plates, and ground reaction force, joint angle, and muscle activity were measured. The motions required to stand up from chairs 30, 40, or 50 cm in height were analyzed with anterior, vertical, and posterior foot placement. With anterior foot placement, the forward-acceleration components of the ground reaction force were recorded with simultaneous and long-sustained activity of the muscles in order to shift the center of gravity of the body forward even more after lift-off. Our findings indicate that the distance between the center of gravity and the point of application of ground reaction force at lift-off are critical factors in the standing-up motion, and that chairs should be of adequate height as well as having sufficient space under the seat to permit the backward movement of the lower legs.

Relationships among age-associated strength changes and physical activity level, limb dominance, and muscle group in women

This study investigated the magnitude and rate of age-associated strength reductions in Australian independent urban-dwelling women and the relationship to muscle groups, limb dominance, and physical activity level. Independent urban-dwelling women aged 20 to 89 years (N = 217) performed maximal voluntary contractions with the dominant and nondominant knee extensors, plantar flexors, and handgrip. Anthropometric measurements were made and questionnaire responses used to obtain current physical activity levels. Trend analysis within analysis of variance and regression analysis on strength was performed. Limb muscle strength was found to be associated with increased age, muscle group, limb dominance, and activity. Self-reported physical activity levels declined with age but women who were more physically active for their age group were stronger in all muscle groups and had more lean body mass and lean thigh and leg cross-sectional area than relatively inactive women. Slopes of the linear reductions of maximal voluntary strength of the knee extensors, plantar flexors, and handgrip with age were significantly different (p < .05) at 9.3%, 7.4%, and 6.2% per decade, respectively. The limb muscle strength of healthy Australian independent and urban-dwelling women aged 20 to 89 years was found to be associated with age and three aspects of disuse: muscle group, relative levels of physical activity, and limb dominance.

Chair and bed rise performance in ADL-impaired congregate housing residents

OBJECTIVES

To examine the ability of activity of daily living (ADL)-impaired older adults to successfully rise, and, when successful, the time taken to rise, from a bed and chair under varying rise task demands.

SETTING

Seven congregate housing facilities

SUBJECTS

Congregate housing residents (n = 116, mean age 82) who admitted to requiring assistance (such as from a person, equipment, or device) in performing at least one of the following mobility-related ADLs: transferring, walking, bathing, and toileting.

METHODS

Subjects performed a series of bed and chair rise tasks where the rise task demand varied according to the head of bed (HOB) height, chair seat height, and use of hands. Bed rise tasks included supine to sit-to-edge, sit up in bed with hand use, and sit up in bed without hands, all performed from a bed where the HOB was adjusted to 0, 30, and 45 degrees elevations; roll to side-lying then rise (HOB 0 degrees); and supine to stand (HOB 0 degrees). Chair seat heights were adjusted according to the percent of the distance between the floor and the knee (% FK), and included rises (1) with hands and then without hands at 140, 120, 100, and 80% FK; (2) from a reclining (105 degrees at chair back) and tilting (seat tilted 10 degrees posteriorly) chair (100% FK); and (3) from a 80% FK seat height with a 4-inch cushion added, with and then without hands. Logistic regression for repeated measures was used to test for differences between tasks in the ability to rise. After log transformation of rise time, a linear effects model was used to compare rise time between tasks.

RESULTS

The median total number of tasks successfully completed was 18 (range, 3-21). Nearly all subjects were able to rise from positions where the starting surface was elevated as long as hand use was unlimited. With the HOB at 30 or 45 degrees essentially all subjects could complete supine to sit-to-edge and sit up with hands. Essentially all subjects could rise from a seat height at 140, 120, and 100% FK as long as hand use was allowed. A small group (8-10%) of subjects was dependent upon hand use to perform the least challenging tasks, such as 140% FK without hands chair rise and 45 degrees sit up without hands. This dependency upon hand use increased significantly as the demand of the task increased, that is, as the HOB or seat height was lowered. Approximately three-quarters of the sample could not rise from a flat (0 degrees HOB elevation) bed or low (80% FK) chair when hand use was not allowed. Similar trends were seen in rise performance time, that is, performance times tended to increase as the HOB or chair seat elevation declined and as hand use was limited. Total self-reported ADL disability, compared to the single ADL transferring item, was a stronger predictor of rise ability and timed rise performance, particularly for chair rise tasks.

CONCLUSIONS

Lowering HOB height and seat height increased bed and chair rise task difficulty, particularly when hand use was restricted. Restricting hand use in low HOB height or lowered seat height conditions may help to identify older adults with declining rise ability. Yet, many of those who could not rise under "without hands" conditions could rise under "with hands" conditions, suggesting that dependency on hand use may be a marker of progressive rise impairment but may not predict day-to-day natural milieu rise performance. Intertask differences in performance time may be statistically significant but are clinically small. Given the relationship between self-reported ADL disability and rise performance, impaired rise performance may be considered a marker for ADL disability. These bed and chair rise tasks can serve as outcomes for an intervention to improve bed and chair rise ability and might also be used in future studies to quantify improvements or declines in function over time, to refine physical therapy protocols, and to examine the effect of bed and chair design modifications on bed and chai

Inter- and intra-individual variability of ground reaction forces during sit-to-stand with principal component analysis

Variable reduction is an important issue in biomechanics, because the definition of a non-redundant set of variables necessary for a complete description of a given motor act provides information about the motor strategy. A systematic tool for dealing with variable reduction problems is Principal Component Analysis. In this paper, as an example of an application of this technique, the set of Ground Reaction Forces (GRFs) provided by a six-component force plate, gained during standing up in a heterogeneous population of 82 normal individuals, was reduced to a set of fewer variables. Each subject was required to stand up from a chair five times at different, randomly self selected, speeds, obtaining a data set of 410 trials. Principal Components (PCs) of GRFs were computed for each trial. On average, over the ensemble of trials, first and second PCs (PC1 and PC2) explained together 90% of PCs. Inter- and intra-individual repeatability of the first two PCs was investigated by examining the correlation coefficient between PC waveforms obtained from the whole set of trials and within the set of trials performed by the same subject, respectively. While the PC1 exhibited repeatable patterns, the second one, although repeatable within the group of trials performed by the same subject, displayed marked inter-individual variability. Therefore, PC1 was related to intrinsic aspects of the motor task and PC2 to inter-subject features.