The Influence Of Lower Body Strength And Physical Activity Intensity On Fast 400-meter Walk Test Performance In Older Adults

INTRODUCTION: The fast-paced 400-meter walk test (fp400MWT) is often used to assess functional capacity and mobility in older adults, predicting outcomes like cardiovascular (CV) disease, physical function limitations, independence, and mortality. Gait speed, derived from the fp400MWT, reflects the influence of lower body strength, coordination, and physical activity (PA), but specific lower body muscle groups and the intensity of PA that underly fp400MWT are less understood. PURPOSE: To compare the independent associations between different lower body muscle group strength measures and the intensity of PA to the fp400MWT in a community-dwelling sample of older adults. METHODS: Sixty-six apparently healthy older adults (mean age = 69.4 ± 10.2 years) completed the fp400MWT, with gait speed measured in m/s. Maximal right-sided isometric strength, measured in kilograms, was assessed for the hip abductor (HA), ankle plantar (AP) ankle dorsi (AD), and knee extensor (KE). Participants also wore a hip-worn triaxial accelerometer for 7-days to determine the average daily time (minutes per day) spent in inactive, light, and moderate-vigorous PA. A Stepwise regression model selection method was used to determine the inclusion of potential explanatory variables from a list of demographic, strength and PA intensity measures with a criteria of p < .05. RESULTS: In the final model, neither age (STD β = - 0.087, p = 0.377) or gender (STD β = - 0.103, p = 0.225) significantly predicted fp400MWT performance. However, HA strength (STD β = 0.465, p < 0.001) and time spent in moderate-vigorous PA (STD β = 0.475, p < 0.001) were significant predictors, with an overall R2 of 62%. CONCLUSIONS: Our results show that HA strength is crucial for walking function in older adults likely due to its role in pelvis stability, balance, and alignment of the knee and ankle. Further, accumulated moderate-vigorous PA positively contributes to walking function through its impact on CV fitness, strength, and coordination. These findings suggest that targeted interventions to strengthen specific lower limb muscle groups and increase time spent in moderate-vigorous PA may ultimately be key to improve functional capacity and slow mobility decline in community-dwelling older adults.