Abstract
BACKGROUND: Weight-bearing jump tests that measure lower-extremity muscle power may be more strongly related to physical performance measures vs. non-weight-bearing leg press power, leg press strength and grip strength. We investigated if multiple muscle function measures differentially related to standard physical performance measures. MATERIALS/METHODS: In the Developmental Epidemiologic Cohort Study (DECOS; N = 68; age 78.5 ± 5.5 years; 57% women; 7% minorities), muscle function measures included power in Watts/kg (functional, weight-bearing: jump; mechanical: Nottingham power rig; Keiser pneumatic leg press) and strength in kg/kg body weight (Keiser pneumatic leg press; hand-held dynamometry). Physical performance outcomes included 6 m usual gait speed (m/s), usual-paced 400 m walk time (seconds), and 5-repeated chair stands speed (stands/s). RESULTS: Women (N = 31; 79.8 ± 5.0 years) had lower muscle function and slower gait speed compared to men (N = 25; 78.7 ± 6.6 years), though similar 400 m walk time and chair stands speed. In partial Pearson correlations adjusted for age, sex, race and height, muscle function measures were moderately to strongly correlated with each other (all p < 0.05), though the individual correlations varied. In multiple regression analyses, each muscle function measure was statistically associated with all physical performance outcomes in models adjusted for age, sex, race, height, self-reported diabetes, self-reported peripheral vascular disease and self-reported pain in legs/feet (all p < 0.05). Jump power (β = 0.75) and grip strength (β = 0.71) had higher magnitudes of association with faster gait speed than lower-extremity power and strength measures (β range: 0.32 to 0.58). Jump power (β = 0.56) had a slightly lower magnitude of association with faster 400 m walk time vs. Keiser power(70% 1-RM) (β = 0.61), and a higher magnitude of association vs. Nottingham power, Keiser strength and grip strength (β range: 0.41 to 0.47). Jump power (β = 0.38) had a lower magnitude of association with chair stands speed than any other power or strength measures (β range: 0.50 to 0.65). CONCLUSIONS: Jump power/kg and grip strength/kg may be more strongly related to faster gait speed, a standard measure of physical function and vital sign related to disability and mortality in older adults, compared to leg press power/strength. However, jump power/kg had a similar magnitude of association with 400 m walk time as Keiser power(70% 1-RM)/kg and a lower magnitude of association with faster chair stands speed than the other muscle function measures. Importantly, choice of muscle function measures should carefully reflect the study focus and methodologic considerations, including population.