The relationship between impairments in muscle performance, functional limitations, and disability in older adults

Many older adults develop restrictions in the performance of activities that are essential to daily living, referred to as functional limitations. Functional limitations can lead to disability, the inability to complete tasks necessary to function in society. A better understanding of how impairments in body systems affect functional limitations and disability in older adults could lead to improved medical management of older adults. The purpose of this study was to examine how impairments in lower extremity muscle performance (strength, power, and endurance) are related to functional limitations and disability in community dwelling older adults. Thirty-four subjects were recruited to participate in this cross-sectional analysis study with 30 individuals completing the study. The Keiser 420 Leg Press was used to measure impairments in lower extremity muscle performance. Functional limitations were classified through the Short Physical Performance Battery, the Six-Minute Walk Test, the Late Life Function and Disability Index (LLFDI) Functional Limitation Component, and average walking speed, average walking distance and average number of steps per day over a six-day period obtained from the AMP 331 physical activity monitor. Disability was measured through the LLFDI Disability Component Limitation Category. Regression analysis was used to examine the direct effect between impairments in muscle performance and functional limitations. Mediation analysis was used to examine the indirect effect of impairments on disability. The results of this study support a relationship between impairments in lower extremity strength and power to functional limitations and disability in community dwelling older adults. Impairments in lower extremity power consistently demonstrated a stronger relationship than strength to all measures of functional limitations and disability. The results of this study did not support a relationship of impairments in endurance to functional limitations or disability. The overall findings of this study would indicate that community dwelling older adults should focus on maintaining and improving lower extremity strength and power across a range of relative intensities in order to decrease functional limitations and disability.