The effect of walking speed on lower-extremity joint powers among elderly adults who exhibit low physical performance.

OBJECTIVES: To compare peak joint powers and joint angles between comfortable and fast walking speeds among a group of elderly adults who exhibit low physical performance, and to test the primary hypothesis that peak ankle powers would not change when walking speed was increased, but that peak hip power output would increase significantly with speed.

DESIGN: Three-dimensional analysis of joint kinematics and kinetics during comfortable and fast walking by both healthy and low-performing elderly adults (age, >70y).

SETTING: Gait laboratory.

PARTICIPANTS: Twenty-four healthy elderly adults and 27 elders who exhibited low performance on a standard battery of walking, standing balance, and chair-rise tasks that places them at risk of mobility-related disability.

INTERVENTIONS: Not applicable.

MAIN OUTCOME MEASURES: Peak lower-extremity joint powers and joint angles.

RESULTS: Low-performing elders increased both ankle and hip power outputs to increase walking speed. However, peak ankle power remained significantly below that of the healthy elderly adults even when the low-performing elders walked at a faster gait speed. Joint-power changes in the low-performing elderly were accompanied by a reduction in hip extension and ankle dorsiflexion, and an increase in transverse pelvic rotation.

CONCLUSIONS: Compared with healthy elderly, the low-performing elderly adults showed speed-independent differences in ankle and hip mechanics that may reflect underlying neuromuscular impairments. In particular, an understanding of the interdependent contributions of hip flexibility and ankle power limitations seem important to inform interventions to maintain gait into advanced age.