Muscle power of the ankle flexors predicts functional performance in community-dwelling older women

OBJECTIVES: To test the hypothesis that peak power of the ankle flexors is related to physical functioning in older women with functional limitations. DESIGN: A cross-sectional study. SETTING: University-based human physiology laboratory. PARTICIPANTS: Thirty-four older women (75.4 ± 5.1 years, 67.8 ± 11.3 kg, body mass index 27.4 ± 4.5) with self-reported functional limitations. MEASUREMENTS: Plantarflexion (PF) and dorsiflexion (DF) peak power and isometric strength with physical performance (stair climb time, repeated chair rise time, maximal and habitual gait velocity) were determined. An isokinetic dynamometer was used to measure isometric strength, isokinetic peak torque and power of PF and DF at five angular velocities (30°, 60°, 90°, 120°, and 180°·sec^-1), and isometric strength. RESULTS: Peak torque for both PF and DF declined with increasing velocity of movement (PF: P < .0001; DF: P < .0001), whereas peak power increased with increasing velocity up to 120°·sec^-1. The strongest univariate associations were found between chair rise time and DF peak power (r = 0.50; P < .002), stair climb time and DF peak power (r = 0.49; P < .003), habitual gait velocity and PF isometric strength (r = 0.53; P < .001), and maximal gait and PF isometric strength (r = 0.47; P < .005). Multivariate regression analysis revealed that DF and PF peak power along with the physical functioning and general health scores from the Medical Outcomes Study Short Form were independent predictors of chair and stair climb performance. CONCLUSION: These data suggest that ankle muscle power together with self-reported measures of health and physical functioning are essential components of functional mobility in older women with functional limitations.