Lower-Extremity Kinetic Response to Weighted-Vest Resistance during Stepping Exercise in Older Adults

Abstract

Stepping activities when wearing a weighted vest may enhance physical function in older persons. Using 3 weighted-vest resistance dosages, this study characterized the lower-extremity joint biomechanics associated with stepping activities in elders. Twenty healthy community-dwelling older adults, ages 74.5 ± 4.5 yrs, performed 3 trials of forward step-up and lateral step-up exercises while wearing a weighted vest which added 0% body weight (BW), 5% BW, or 10% BW. They performed these activities on a force platform while instrumented for biomechanical analysis. Repeated-measures ANOVA was used to evaluate the differences in ankle, knee, and hip maximum joint angles, peak net joint moments, joint powers, and impulses among both steping activities and the 3 loading conditions. Findings indicated that the 5% BW vest increased the kinetic output associated with the exercise activities at all three lower-extremity joints. These increases ranged from 5.9% for peak hip power to 12.5% for knee extensor impulse. The application of an additional 5% BW resistance did not affect peak joint moments or powers, but it did increase the joint impulses by 4–11%. Comparisons between exercise activities, across the 3 loading conditions, indicated that forward stepping preferentially targeted the hip extensors while lateral stepping targeted the plantar flexors; both activities equally targeted the knee extensors. Weighted-vest loads of 5% and 10% BW substantially increased the mechanical demand on the knee extensors, hip extensors (forward stepping), and ankle plantar flexors (lateral stepping).