Role of muscle mass and muscle quality in the association between diabetes and gait speed

OBJECTIVE

Older people with type 2 diabetes are at high risk of mobility disability. We investigated the association of diabetes with lower-limb muscle mass and muscle quality to verify whether diabetes-related muscle impairments mediate the association between diabetes and low walking speed.

RESEARCH DESIGN AND METHODS

We performed a cross-sectional analysis of 835 participants (65 years old and older) enrolled in the InCHIANTI (Invecchiare in Chianti, aging in the Chianti area) population-based study. Total, muscular, and fat cross-sectional areas of the calf and relative muscle density were measured using peripheral quantitative computerized tomography. Indicators of muscle performance included knee-extension torque, ankle plantar flexion and dorsiflexion strength, lower-extremity muscle power, and ankle muscle quality (ratio of ankle strength to the muscle area [kilograms per centimeters squared]). Gait performance was assessed by 4- and 400-m walking speed. Diabetes was ascertained by standard American Diabetes Association criteria.

RESULTS

Prevalence of diabetes was 11.4%. After adjustment for age and sex, participants with diabetes had lower muscle density, knee and ankle strength, and muscle power and worse muscle quality (all P < 0.05). Diabetic participants were also slower on both 4-m (β: −0.115 ± 0.024 m/s, P < 0.001) and 400-m (β:−0.053 ± 0.023 m/s, P < 0.05) walking tests. In multivariable linear regression models, lower-limb muscle characteristics accounted for 24.3 and 15.1% of walking speed difference comparing diabetic and nondiabetic subjects in the 4- and 400-m walks, respectively.

CONCLUSIONS

In older persons, diabetes is associated with reduced muscle strength and worse muscle quality. These impairments are important contributors of walking limitations related to diabetes.Walking performance has been shown to reflect health and functional status in older adults, and in observational studies walking speed is a powerful predictor of survival (1) and long-term risk of disability (2). Type 2 diabetes has been consistently reported to be one of the strongest correlates of the presence of poor walking performance or mobility difficulty (3), and older patients with diabetes are at high risk of future mobility disability and loss of independence (4,5). However, the mechanisms for impaired walking in diabetes have been poorly understood (6). Traditional long-term complications and diabetes-related comorbidities only partially explain the excess risk of disability associated with diabetes. For example, in the Women’s Health and Aging Study, chronic conditions including cardiovascular diseases, peripheral arterial disease, peripheral neuropathy, overweight, depression, and visual impairment explained <60% of the risk of severe walking limitation (7).Lower-extremity muscle strength and muscle quality are strong determinants of walking performance and powerful predictors of the risk of mobility limitation (8,9). Cross-sectional and longitudinal analyses of the Health Aging and Body Composition study have demonstrated that older diabetic individuals had lower muscle strength and muscle quality compared with their nondiabetic counterparts (10,11). These analyses also demonstrated that older persons with type 2 diabetes had accelerated loss of muscle strength over time, suggesting an additional biological mechanism to explain the association between diabetes and poor physical function (12). Nevertheless, whether diabetes-related muscle impairments mediate the association between diabetes and low walking speed has never been investigated.To address this question, we assessed walking performance and lower-extremity muscle mass, strength, and power in a sample of older Italian persons with and without diabetes enrolled in the InCHIANTI (Invecchiare in Chianti, aging in the Chianti area) study, a population-based study designed to elucidate how specific impairment in physiological subsystems may influence walking ability in older persons (13). We hypothesized that compared with persons without diabetes, those with diabetes would have poorer skeletal muscle performance and that these muscle impairments would account for at least part of the slower walking speed observed in persons with diabetes.     

Compensatory strategies used by older adults facing mobility disability

Preclinical disability in mobility tasks can be recognized by asking people without overt mobility disability whether they have changed the way, either the manner or the frequency, of doing a mobility task because of a health or physical condition. Like other compensatory strategies, preclinical mobility disability has a dual nature as both a risk marker associated with impairment or limitation and a mediating factor affecting the natural history of disability. The method of ascertaining preclinical disability through self-report has been shown to have construct validity, to be reliable, and to identify people at an elevated risk of developing overt mobility disability over 1 to 2 years. Many worthy research questions in this field remain to be addressed, especially regarding qualitative heterogeneity (doing more vs doing less) and interactions among compensatory strategies. Nonetheless, there is sufficient evidence to apply what is known about preclinical disability to screening in clinical settings. This area of research and practice constitutes an opportunity for physical medicine and rehabilitation and geriatric medicine to jointly make a large beneficial impact on population health through strategies to prevent disability because rapidly growing numbers of older adults will experience this early and potentially malleable stage.     

Exploring how peak leg power and usual gait speed are linked to late-life disability: data from the National Health and Nutrition Examination Survey (NHANES), 1999-2002

OBJECTIVE: To investigate the relation of both peak leg power and usual gait speed in their association with varying domains of late-life disability. DESIGN: Participants (> or =60 yrs of age, n = 1753) were from the National Health and Nutrition Examination Survey, 1999-2002. Disability in activities of daily living, instrumental activities of daily living, leisure and social activities, lower limb mobility, and general physical activities was obtained by self-report. Peak muscle power was the product of isokinetic peak leg torque and peak force velocity. Functional limitations were evaluated via usual gait speed, which was obtained from a 20-foot timed walk. RESULTS: Low usual gait speed was associated with disability independent of basic demographics, cognitive performance, co-morbidities, health behaviors, and inflammatory markers. The odds ratios for disabilities in activities of daily living, instrumental activities of daily living, leisure and social activities, lower limb mobility, and general physical activities for each standard-deviation increase in walking speed were 0.72 (95% confidence interval [CI], 0.59-0.87), 0.63 (95% CI, 0.52-0.77), 0.57 (95% CI, 0.45-0.72), 0.56 (95% CI, 0.47-0.67), and 0.74 (95% CI, 0.64-0.85), respectively. The odds ratios for disabilities in activities of daily living, instrumental activities of daily living, leisure and social activities, lower limb mobility, and general physical activities for each standard-deviation increase in leg power were 0.70 (95% CI, 0.55-0.89), 0.67 (95% CI, 0.53-0.86), 0.62 (95% CI, 0.47-0.83), 0.58 (95% CI, 0.47-0.72), and 0.73 (95% CI, 0.61-0.87), respectively. Supplementary adjustment for walking speed mildly attenuated the relation of leg power to disability. CONCLUSION: Peak leg power and habitual gait speed were associated with varying domains of late-life disability. The association between peak leg power and disability seems to be partially mediated through usual gait speed.     

The pathway from musculoskeletal pain to mobility difficulty in older disabled women

Little is known about the pathway from musculoskeletal pain to mobility difficulty among older persons. We examined potential physical and psychological mediators of the pain-disability relationship in the Women's Health and Aging Study (WHAS), a cohort of women aged 65 who had at least mild disability at baseline. Pain was classified according to location and severity (widespread pain; lower extremity pain; other pain; none or mild pain in only one site). Among women without a lot of difficulty in stair climbing (n=676) or walking (n=510) at baseline, those who reported widespread pain were more likely than those with none or mild pain to develop a lot of difficulty with mobility during the 3 year follow-up. The likelihood for mobility difficulty was unchanged after adjusting for physical impairments and symptoms of depression and anxiety (walking aOR=1.85, 95%CI, 1.08-3.17; stair climbing, aOR=2.68, 95%CI, 1.56-4.62). Lower extremity pain was associated with increased likelihood for difficulty with climbing stairs but not with walking. However, this association was attenuated after adjusting for physical impairments and psychological symptoms (aOR=1.66, 95%CI, 0.99-2.77). Pain was not associated with increased risk for becoming unable to walk or climb stairs. The findings suggest that pain is a unique domain as a cause of disablement, independent of the usual pathway to disability via physical impairments. Research is needed to better understand the development of pain-related disability in order to determine optimum approaches to prevent and treat mobility disability in older persons with persistent pain.     

Preliminary effectiveness of a sequential exercise intervention on gait function in ambulant patients with multiple sclerosis — A pilot study

BackgroundPatients with multiple sclerosis (pwMS) often experience a decline in motor function and performance during prolonged walking, which potentially is associated with reduced ankle push-off power and might be alleviated through structured exercise. The objectives of this pilot study were to assess ankle push-off power and walking performance in pwMS and healthy controls, and the preliminary effectiveness of a sequential exercise program (resistance training followed by walking-specific endurance training) on ankle push-off power and walking performance.MethodsPwMS (N = 10) with self-reported reduced walking performance and healthy controls (N = 10; at baseline only) underwent 3D gait analysis during a self-paced 12-minute walking test to assess walking performance prior to and following a sequential exercise program. Secondary testing paradigms comprised isometric muscle testing (triceps surae), cardiopulmonary exercise testing and self-report measures.FindingsPwMS had a shorter 12-minute walking distance, and lower peak ankle push-off power (most-affected leg) in comparison to healthy controls. There was no minute-to-minute decline in walking performance. The 8-week resistance training significantly improved walking distance. In parallel, higher peak and speed-normalized ankle push-off power were found in the less-affected side. No additional changes were found following the walking-specific endurance training phase.InterpretationThere was no walking-related motor fatigue found during a self-paced 12-minute walking test despite reduced ankle push-off power, and self-reported walking problems. Preliminary effects suggest a positive effect of resistance training on walking performance, potentially associated with increases in ankle push-off power, interestingly, in the less-affected leg. The added effect of the walking-specific endurance training remains unclear.     

occupational physical activity and the development of impaired mobility: the 12-year follow-up of the Baltimore Epidemiologic Catchment Area sample

OBJECTIVE: To examine the association between occupational physical activity and self-reported disability. DESIGN: Population-based case control analysis of a longitudinal population-based study in east Baltimore. Eligible participants were aged 18 to 29 yr in 1981, had complete information on occupation in 1981, no disability with tasks related to the domain of mobility in 1981, and complete information on mobility function in 1993 (n = 174). Occupations were divided into low, moderate, and high metabolic equivalents based on job category in 1981. The main outcome measure was disability defined by self-report of difficulty in one or more of five exercise mobility tasks in 1993. RESULTS: Of 174 eligible participants, 45 (26%) reported the onset of disability at follow-up in 1993. A crude odds ratio of 0.25 (95% confidence interval, 0.06, 0.82) was found for the association of moderate compared with low occupational physical activity and the risk of incident disability in mobility tasks. After adjustments to control for possible confounders, moderate job metabolic activity (1.8-2.9 Mets) was independently protective against disability in this cohort (odds ratio = 0.25; 95% confidence interval = 0.083, 0.783). CONCLUSION: In this cohort of people aged 18 to 29 yr, a moderate amount of occupational physical activity was protective against disability in mobility tasks.     

Effects of Aquatic Resistance Training on Mobility Limitation and Lower-Limb Impairments After Knee Replacement

Valtonen A, Pöyhönen T, Sipilä S, Heinonen A. Effects of aquatic resistance training on mobility limitation and lower-limb impairments after knee replacement.

Objective

To study the effects of aquatic resistance training on mobility, muscle power, and cross-sectional area.

Design

Randomized controlled trial.

Setting

Research laboratory and hospital rehabilitation pool.

Participants

Population-based sample (N=50) of eligible women and men 55 to 75 years old 4 to 18 months after unilateral knee replacement with no contraindications who were willing to participate in the trial.

Interventions

Twelve-week progressive aquatic resistance training (n=26) or no intervention (n=24).

Main Outcome Measures

Mobility limitation assessed by walking speed and stair ascending time, and self-reported physical functional difficulty, pain, and stiffness assessed by Western Ontario and McMaster University Osteoarthritis Index (WOMAC) questionnaire. Knee extensor power and knee flexor power assessed isokinetically, and thigh muscle cross-sectional area (CSA) by computed tomography.

Results

Compared with the change in the control group, habitual walking speed increased by 9% (P=.005) and stair ascending time decreased by 15% (P=.006) in the aquatic training group. There was no significant difference between the groups in the WOMAC scores. The training increased knee extensor power by 32% (P<.001) in the operated and 10% (P=.001) in the nonoperated leg, and knee flexor power by 48% (P=.003) in the operated and 8% (P=.002) in the nonoperated leg compared with controls. The mean increase in thigh muscle CSA of the operated leg was 3% (P=.018) and that of the nonoperated leg 2% (P=.019) after training compared with controls.

Conclusions

Progressive aquatic resistance training had favorable effects on mobility limitation by increasing walking speed and decreasing stair ascending time. In addition, training increased lower limb muscle power and muscle CSA. Resistance training in water is a feasible mode of rehabilitation that has wide-ranging positive effects on patients after knee replacement surgery.     

Estimating transition probabilities in mobility and total costs for medicare beneficiaries

Hoffman JM, Ciol MA, Huynh M, Chan L. Estimating transition probabilities in mobility and total costs for Medicare beneficiaries.

Objective

To examine how persons move back and forth along levels of mobility disability.

Design

Self-reported mobility limitations were used to create categories of annual transition states. The total cost to Medicare associated with each year was calculated for each participant. In addition, we examined cost relative to transition state, adjusting for demographic and other health status variables.

Setting

National survey.

Participants

Participants in the longitudinal Medicare Current Beneficiary Survey from 1992 to 2005.

Interventions

Not applicable.

Main Outcome Measures

Annual self-reported mobility limitations and total Medi costs.

Results

Most participants remained without mobility limitations or improved over time. Reported average costs were 10 times higher for those who transitioned to severe limitations, unable to walk, or death compared with persons who reported no mobility limitation. Estimated costs were highest for those transitioning to increased states of disability and to death.

Conclusions

Mobility limitations in older adults are dynamic, and improvement (as measured by annual transitions) occurred for a large number of Medicare beneficiaries. High total annual costs were observed in groups that transitioned to worsening mobility states, suggesting a link between mobility limitation transitions and cost. Prevention and treatment of mobility limitation may be an important factor to consider in health care reform.     

Trunk and foot acceleration variability during walking relates to fall history and clinical disability in persons with multiple sclerosis

BackgroundPersons with multiple sclerosis are often at higher risk for falling, but clinical disability scales and fall risk questionnaires are subjective and don't provide specific feedback about why an individual is unstable. The purpose of this study was to determine how relationships between trunk and foot acceleration variability relate to physiological impairments, clinical disability scales, and mobility questionnaires in persons with multiple sclerosis.Methods15 fallers and 25 non-fallers with multiple sclerosis walked on a treadmill at normal walking speed while trunk and foot accelerations were recorded with wireless accelerometers and variability measures were extracted and used to calculate the gait stability index metrics as a ratio of trunk acceleration variability divided foot acceleration variability. Subjects' sensorimotor delays and lower extremity vibration sensitivity were tested. Subjects also completed clinical disability scales (Guy's Neurological Disability Scale and Patient Reported Expanded Disability Status Scale) and mobility questionnaires (Falls Efficacy Scale, Activities Balance Confidence Scale, 12 Item Multiple Sclerosis Walk Scale).FindingsMultiple gait stability index metrics were significantly correlated with clinical measures of disability and mobility in multiple sclerosis subjects (r = 0.354–0.528), but no correlations were found for sensorimotor delays or lower extremity sensation. Multiple gait stability indices performed at least as well as clinical questionnaires for separating fallers from non-fallers.InterpretationThe gait stability indices can potentially be used outside of a laboratory setting to measure walking characteristics related to fall history and disability level in people with multiple sclerosis.     

Effects of testosterone therapy on muscle performance and physical function in older men with mobility limitations (The TOM Trial): design and methods

The TOM study is the first, single-site, placebo-controlled, randomized clinical trial designed to comprehensively determine the effects of testosterone administration on muscle strength and physical function in older men with mobility limitations. A total of 252 community dwelling individuals aged 65 and older with low testosterone levels and self-reported limitations in mobility and short physical performance battery (SPPB) scores between 4 and 9 will be randomized to receive either placebo or testosterone therapy for 6 months. The primary objective is to determine whether testosterone therapy improves maximal voluntary muscle strength as quantified by the one repetition maximum. Secondary outcomes will include measures of physical function (walking, stair climbing and a lifting and lowering task), habitual physical activity and self-reported disability. The effects of testosterone on affect, fatigue and sense of well being will also be assessed. Unique aspects of the TOM Trial include selection of men with self-reported as well as objectively demonstrable functional limitations, community-based screening and recruitment, adjustment of testosterone dose to ensure serum testosterone levels in the target range while maintaining blinding, and inclusion of a range of self-reported and performance-based physical function measures as outcomes. Clinicaltrials.gov identifier: NCT00240981.     

Comorbidities and impairments explaining the association between diabetes and lower extremity disability: The Women's Health and Aging Study

OBJECTIVE: To elucidate the role of diabetes-related impairments and comorbidities in the association between diabetes and physical disability, this study examined the association between diabetes and lower extremity function in a sample of disabled older women. RESEARCH DESIGN AND METHODS: Cross-sectional analysis of 1,002 women (aged >or=65 years) enrolled in the Women's Health and Aging Study (one-third most disabled of the total community-dwelling population). Diabetes and other medical conditions were ascertained by standard criteria that used multiple sources of information. Functional status was assessed using self-reported and objective performance measures. RESULTS: Women with diabetes were significantly more likely to have cardiovascular diseases, peripheral nerve dysfunction, visual impairment, obesity, and depression. After adjustment for age, women with diabetes had a greater prevalence of mobility disability (odds ratio [OR] 1.85, 95% CI 1.12-3.06), activities of daily living disability (1.61, 1.06-2.43), and severe walking limitation (2.34, 1.56-3.50), and their summary mobility performance score (0-12 scale based on balance, gait speed, chair stands) was 1.4 points lower than in nondiabetic women (P < 0.001). Peripheral artery disease, peripheral nerve dysfunction, and depression were the main individual contributing factors; however, none of these conditions alone fully explained the association between diabetes and disability. Conversely, only after adjusting for all potential mediators was the relationship between diabetes and disability reduced to a large degree. CONCLUSIONS: Even among physically impaired older women, diabetes is associated with a major burden of disability. A wide range of impairments and comorbidities explains the diabetes-disability relationship, suggesting that the mechanism for such an association is multifactorial.     

Physical disability after severe lower-extremity injury

OBJECTIVE: To investigate the use of a combined measure of decreased walking speed and gait deviation to identify high physical disability in patients with lower-limb salvage. DESIGN: Longitudinal study of patients with severe lower-extremity trauma. SETTING: Eight level I trauma centers. PARTICIPANTS: Patients (N=276) with lower-limb salvage from the Lower Extremity Assessment Project. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Disability from the physical dimension of the Sickness Impact Profile (SIP), walking speed, and gait deviation were measured at 24 months of follow-up. A 1-way analysis of variance and planned comparisons compared mean SIP scores across and between the following 3 outcome groups: no impaired speed and no gait deviation, impaired speed or gait deviation, and impaired speed and gait deviation. RESULTS: Mean SIP scores for the physical dimension and its 2 categories of ambulation and body care and movement differed statistically across the planned comparisons. The mobility category showed that the impaired speed or deviation group was statistically similar to the group without impaired speed and gait deviation. CONCLUSIONS: The combination of decreased walking speed and gait deviation appears to provide a valid measure of physical disability among patients with lower-limb salvage.     

Neuromuscular stimulation of the quadriceps muscle after hip fracture: a randomized controlled trial

OBJECTIVE: To study the feasibility and effect of neuromuscular stimulation on recovery of mobility after surgical fixation for hip fracture. DESIGN: Double-blind study with stratified randomization. SETTING: Home-based rehabilitation program. PARTICIPANTS: Twenty-four women over the age of 75 years with hip fracture. INTERVENTIONS: Neuromuscular or placebo stimulation of the quadriceps muscle of the fractured leg, applied for 3 hours a day, for 6 weeks, commencing 1 week after surgery. MAIN OUTCOME MEASURES: Recovery of walking speed and ability, postural stability, lower-limb muscle power, and pain at 7 and 13 weeks after surgery. RESULTS: Women in the neuromuscular stimulation group showed faster recovery of mobility. Of the women receiving stimulation, 9 of 12 recovered their prior levels of indoor mobility ability by 13 weeks compared with 3 of 12 in the placebo group (Fisher exact test, P=.046). There were no differences in recovery of walking speed in the first 7 weeks, but women in the stimulation group had greater recovery between 7 and 13 weeks (mean difference=-.13m/s; 95% confidence interval, -.23 to -.01). CONCLUSIONS: Neuromuscular stimulation at home is feasible and may be effective in speeding recovery of mobility after surgical fixation of hip fracture.     

Disability Among Persons With Chronic Severe Back Pain: Results From a Nationally Representative Population-based Sample

We evaluated the association between the chronic severe back pain with disability and participation, in U.S. Adults using data from the US 2019 National Health Interview Survey. In our sample of 2,925 adults (weighted n: 20,468,134) who reported having chronic severe back pain, 60% reported mobility disability, 60% had work limitations, 34% were limited for social participation and 16% had self-care limitations. Older age (65+) was associated with mobility difficulties (OR 1.99, 95% CI 1.28,6.09) and work limitation (OR 2.21, 95% CI 1.61,3.05). Lower socioeconomic status was associated with increasing odds of disability across the 4 categories. Being obese was only associated with mobility difficulties (OR 1.95, 95% CI 1.41,2.71), while not working in the past week was associated with difficulties in mobility (OR 3.55, 95% CI 2.64,4.75), self-care (OR 3.34, 95% CI 2.20,5.08), and social participation (OR 3.20, 95% CI 2.13,4.80). Comorbidities were highly associated with limitations in all 4 categories. Those deeming their ability to manage their pain ineffective were twice as likely to have limitations in self-care, social and work participation but not mobility. Identifying factors associated with disability and limitation may help target appropriate management for persons with chronic pain at high risk for disability.PerspectiveWe evaluated the association between the chronic severe back pain with disability and participation, in a representative sample of Americans. Identifying factors associated with a likelihood of disability may help target appropriate pain management for persons at high risk for disability due to chronic severe back pain.     

Leg extension power asymmetry and mobility limitation in healthy older women

OBJECTIVE: To investigate the association of asymmetry in leg extension power (LEP) with walking and standing balance. DESIGN: Cross-sectional analysis. SETTING: Research laboratory. PARTICIPANTS: Healthy female twins (N=419), ages 63 to 75 years. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: The LEP difference between the stronger and the weaker leg, measured with the Nottingham power rig, was calculated. Ten-meter maximal walking velocity was assessed in a laboratory corridor on a wide (170 cm) and narrow (35 cm) track, and the ability to maintain tandem stance for 20 seconds was recorded. RESULTS: The mean LEP difference +/- standard deviation between the legs was 15%+/-9% (P<.001). Those with large LEP difference had lower walking velocity and poorer standing balance than those with small LEP difference, in particular when the LEP of the stronger leg was below the median. CONCLUSIONS: Even in healthy older women, substantial LEP asymmetry between the lower limbs was present, encumbering walking and standing balance. Lower-limb muscle power asymmetry warrants further study in order to develop well-targeted strategies for preventing mobility limitation in older people.     

Role of walking-exercise therapy after stroke

Stroke commonly leads to reduced mobility, which leads to deconditioning and a worsening of vascular risk factors, such as diabetes. The worsened risk profile leads to further strokes and disability – a vicious cycle for the stroke survivor. Exercise (walking) therapy may break this cycle by providing adequate stimuli for improving gait through plastic adaptation in the brain and through increasing fitness. Randomized, controlled data demonstrate the efficacy for gains in fitness and walking speed, the latter being related to lasting changes in activation patterns of the brainstem and cerebellum. Diabetes and muscle inflammation can also be improved by aerobic exercise training. The scope of this review summarizes these data and identifies unresolved issues related to optimization, intensity and maintenance of therapy effects. Exercise should be an integral part of every rehabilitation program.     

How is walking speed related to muscle strength? A study of healthy persons and persons with late effects of polio

OBJECTIVES: To evaluate the relationship between walking speed and muscle strength in the lower extremities in healthy persons and in persons with late effects of polio and to compare the models for these relationships. DESIGN: Retrospective analysis. SETTING: University hospital department. PARTICIPANTS: An urban sample of 144 healthy men and women (age range, 40-79 y) and 234 (146 women, 88 men) subjects with late polio. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Muscle strength in the lower extremities was measured and combined into an index. Walking speed for spontaneous and maximal walking was measured. A nonlinear regression model was developed. RESULTS: Evidence was provided for the nonlinear relationship between walking speed and strength. A specific strength threshold could not be identified. The asymptote of this curve for maximal walking was 2.57 m/s in the healthy group and 2.02 m/s in the subjects with late effects of polio. A high body mass index (>25 kg/m2) lowered the asymptote. CONCLUSIONS: It is important to prevent strength decrease that approaches the critical level where a further reduction affects walking speed more evidently. The difference in the relationship between muscle strength and walking speed for the 2 groups studied may partly depend on biomechanic imbalance between muscle groups.     

Physical impairment and disability: relationship to performance of activities of daily living in community-dwelling older men

BACKGROUND AND PURPOSE: The decline of physical function of older adults, associated with loss of independent living status, is a major public health concern. The purpose of this study was to examine the relationship of physical impairment and disability to performance of activities of daily living (ADL) among community-dwelling older adults. SUBJECTS AND METHODS: Eighty-three community-dwelling older men who were referred to a comprehensive outpatient geriatric evaluation program (mean age=75.5 years, SD=7.0, range=64-97) were examined. Measurements of physical impairment (muscle force production, flexibility, and fitness) and physical disability (gait speed, stride length, risk for recurrent falls, and physical function) were recorded. RESULTS: A stepwise linear regression was used to determine the relationship of physical impairments and disability measures with ADL. The results indicated that walking speed, fall risk, and muscle force contributed independently to the characterization of the activities of daily living of the community-dwelling older men studied (adjusted R2=.68; F=56.81; df=3,80; P<.001). Using a principal components factor analysis, 4 domains were identified that explained 68.2% of the variance in performance of ADL: (1) mobility/fall risk=26.5%, (2) coordination=15%, (3) fitness=14.7%, and (4) flexibility=12.0%. DISCUSSION AND CONCLUSION: The identification of domains of physical function may be useful to physical therapists in the development of interventions targeted for physical impairments and disabilities that contribute to deficits in performance of ADL. Targeting interventions for physical impairments and disabilities related to function may improve the effectiveness of physical therapist interventions and reduce the loss of independence among community-dwelling older people.     

Physiologic costs of computer-controlled walking in persons with paraplegia using a reciprocating-gait orthosis

Blood pressure, heart rate, oxygen uptake, cardiac output, and the surface electromyogram from key muscle groups in the upper body were measured in four subjects with paraplegia during ambulation using only a reciprocating-gait orthosis (RGO) and using an RGO with movement assisted by functional electrical stimulation (FES) of the hamstring and gluteus maximus muscles. These data were compared to data collected on four able-bodied control subjects during ambulation at matched speeds. Whether walking with FES and RGOs or walking with RGOs alone, subjects had an optimum gait speed at which efficiency was highest. For paralyzed subjects using FES, the optimum walking speed was approximately 1.5 mph (2.4km/hr); without FES, the optimum speed averaged about 0.75mph (1.2km/hr). Blood pressure, heart rate, oxygen uptake, and cardiac output were measured during ambulation with FES and were found to be higher than those of controls, but they were significantly lower than those in the paralyzed subjects in RGOs with no FES. Electromyogram studies showed that the activity in upper body muscles was much higher when walking in RGOs without FES than in RGOs with FES.