Biomedical subjects

Seth Herman

Publications and source records attributed to Seth Herman.

5 recordsLinked to original sources

PubMed2005

Upper and lower limb muscle power relationships in mobility-limited older adults.

BACKGROUND: Lower limb muscle power impairments are modifiable factors underlying mobility limitations in older adults. This study examined relationships between upper and lower limb muscle power and their role in predicting mobility performance among community-dwelling older adults. METHODS: A cross-sectional analysis was conducted. Participants included 37 mobility-limited adults (24 women, 13 men), aged 65 to 93 years. Measures included upper (elbow extension) and lower limb (double leg press) one repetition maximum (1RM), and muscle power at both 40% and 70% one repetition maximum. Physical performance measures included stair climb time, the Short Physical Performance Battery, and 4-meter walk time. Factors commonly mediating the relationship between impairments and physical performance were analyzed as covariates. RESULTS: Participants had a mean age of 76 years, had five chronic medical conditions, and manifested moderate mobility limitations. Although the associations between the upper and lower limbs were strong (p <.001), the magnitude of association was greater for power (r =.88-.89) as compared to strength (r =.69). Multivariate regression analyses revealed consistently strong relationships between limb muscle power and mobility performance measures. Substituting upper for lower limb power within these models did not materially weaken the relationships. CONCLUSION: Muscle power appears to be a more generalized attribute between the upper and lower limbs than is muscle strength, suggesting that mechanisms underlying velocity of movement, as opposed to force production, may be important factors underlying muscle power in elderly persons. Additionally, upper limb muscle power measures may serve as a useful surrogate measure of limb power having implications for clinicians and researchers.

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PubMed2004

Increased Velocity Exercise Specific to Task (InVEST) training: a pilot study exploring effects on leg power, balance, and mobility in community-dwelling older women.

OBJECTIVES: To evaluate a dynamic form of weighted vest exercise suitable for home use and designed to enhance muscle power, balance, and mobility. DESIGN: A single-blind, randomized, controlled trial. SETTING: Outpatient exercise research facility situated within an academic long-term care center. PARTICIPANTS: Twenty-one community-dwelling women aged 70 and older with a Short Physical Performance Battery (SPPB) score between 4 and 10 (out of 12). INTERVENTIONS: Subjects were randomized into a progressive resistance-training program using weighted vests for resistance with exercises designed to be specific to mobility tasks and have a component performed at the fastest possible velocity (Increased Velocity Exercise Specific to Task (InVEST), n=11) or a control exercise group (control, n=10), which performed slow-velocity, low-resistance exercise. Both groups exercised three times a week for 12 weeks. MEASUREMENTS: Changes in muscle power, balance, and physical performance were compared. RESULTS: In comparison to control group, InVEST group manifested significant improvements (P<.05) in leg power across measurements obtained at 75% to 90% of the one-repetition maximum. Both groups demonstrated significant improvements in chair stand and SPPB score from baseline, and the InVEST group showed significant improvements in gait speed and chair stand from baseline (P<.05). InVEST produced significantly greater changes in chair stand time than control (P<.05). CONCLUSION: InVEST training appears be an effective means of enhancing leg power and chair rise in this population and is worthy of further investigation as a means of enhancing balance and mobility.

Age Factors↗

PubMed2002

The relationship between leg power and physical performance in mobility-limited older people.

OBJECTIVES: The purpose of this study was to assess the influence of leg power and leg strength on the physical performance of community-dwelling mobility-limited older people. DESIGN: Cross-sectional analysis of baseline data from a 12-week randomized controlled exercise-intervention study. SETTING: Exercise laboratory within the Department of Health Science of an urban university. PARTICIPANTS: Forty-five community-dwelling mobility-limited people (34 women, 11 men), aged 65 to 83. MEASUREMENTS: Health status, depression, cognition, physical activity, and falls efficacy; physiological measures of lower extremity strength and power; and measures of physical performance. RESULTS: Through bivariate analyses, leg power was significantly associated with physical performance as measured by stair-climb time, chair-stand time, tandem gait, habitual gait, maximal gait, and the short physical performance battery describing between 12% and 45% of the variance (R2). Although leg power and leg strength were greatly correlated (r = .89) in a comparison of bivariate analyses of strength or power with physical performance, leg power modeled up to 8% more of the variance for five of six physical performance measures. Despite limitations in sample size, it appeared that, through quadratic modeling,the influence of leg power on physical performance was curvilinear. Using separate multivariate analyses, partial R2 values for leg power and leg strength were compared, demonstrating that leg power accounted for 2% to 8% more of the variance with all measures of physical performance. CONCLUSION: Leg power is an important factor influencing the physical performance of mobility-limited older people. Although related to strength, it is a separate attribute that may exert a greater influence on physical performance. These findings have important implications for clinicians practicing geriatric rehabilitation.

Age Factors↗

PubMed2002

Weighted stair climbing in mobility-limited older people: a pilot study.

OBJECTIVES: To evaluate weighted stair climbing exercise (SCE) as a means of increasing lower extremity muscle power in mobility-limited older people. DESIGN: Single-blinded, randomized controlled pilot study. SETTING: Human physiology laboratory of a metropolitan university. PARTICIPANTS: Forty-five community-dwelling people aged 65 and older who had baseline mobility limitations manifested by scores of 11 or lower on the Short Physical Performance Battery (SPPB). INTERVENTIONS: Subjects were randomized into one of two 12-week exercise programs. The intervention group (SCE) (n = 23) ascended and descended stairs, at a set pace, while wearing a weighted vest. The control group (WALK) (n = 22) participated in a standardized walking program. MEASUREMENTS: Primary and secondary outcomes included measures of muscle power and strength, submaximal aerobic capacity, and physical performance. RESULTS: SCE produced 17% improvement in double leg press peak power in comparison with WALK (P =.013) and significant improvement in stair climbing power from baseline (12%). Improvement in submaximal aerobic performance was equivalent for both groups. Although not statistically significant, effect size estimates suggest that SCE can potentially influence knee extension power and strength. Stair climb time was improved in both groups, whereas SCE produced significant improvements from baseline SPPB score in a subcohort of participants. CONCLUSIONS: These findings suggest that SCE maybe a useful component of a home exercise program designed to enhance lower extremity muscle power, aerobic capacity, and functional performance. Further investigation is needed involving larger sample sizes and direct comparisons with other forms of resistance training.

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PubMed2002

The 6-minute walk test in mobility-limited elders: what is being measured?

BACKGROUND: The 6-minute walk (6mw) is a well-established measure of aerobic capacity in elders with cardiorespiratory and peripheral vascular disease and may be an accurate measure of functional performance in healthy elders. In mobility-limited elders, a population at risk for disability, impairments in strength and power are predictive of performance-based measures of function. Though commonly utilized as an outcome measure among otherwise healthy mobility-limited elders, it is not clear whether the 6mw best represents a measure of functional limitation, aerobic capacity, or both. METHODS: We hypothesized that the 6mw would be strongly representative of performance-based measures of function being determined by impairments in muscle strength and power. We performed a cross-sectional analysis of 45 community-dwelling elders with mild to moderate mobility limitations. RESULTS: The 6mw was strongly associated with established functional measures (r =.61-.83; p <.001), but was poorly associated with indirect measures of aerobic capacity (r <.25; p >.05). Multivariate linear regression models demonstrated that impairments in leg strength and power, especially those at the knee and ankle, were predictive of 6mw performance. CONCLUSIONS: These findings emphasize the 6mw as a measure of functional limitation among mobility-limited elders without cardiorespiratory or peripheral vascular disease.

Activities of Daily Living↗