Association between physical activity bout length and physical functioning in older adults using absolute and relative intensity thresholds: a longitudinal cohort study

Abstract

Abstract Background Defining moderate-to-vigorous physical activity (MVPA) relative to individual capacity, instead of absolute intensity cut-points, may provide a more meaningful representation of physical activity in relation to age-related decline in physical functioning. We examined whether associations between MVPA energy expenditure (MVPAEE) and changes in physical functioning differ when MVPA is defined using absolute versus relative intensity cut-points, and whether bout length modifies these associations in older adults. Methods This 4-year follow-up study included 295 community-dwelling participants aged 75, 80, and 85 at baseline. Physical functioning was assessed using 6-min walking distance (6MWD) and five-times sit-to-stand test (FTSTS) time. MVPAEE was measured using thigh-worn accelerometers combined with chest-worn electrocardiography. MVPAEE accumulated in bouts of varying lengths was defined using both absolute intensity cut-points and cut-points relative to individual capacity. Associations between baseline MVPAEE and changes in physical functioning were examined using linear regression models and compositional data analysis. Results Physical functioning declined during the follow-up. Higher relative MVPAEE was associated with a smaller decline in 6MWD (β = 0.27, 95% CI [0.08, 0.46]). Compositional data analyses showed that a higher proportion of MVPA relative to light-intensity activity energy expenditure was associated with a smaller decline in 6MWD (βilr = 0.25-0.31), independent of bout length. Absolute MVPAEE and bout-specific accumulation were not associated with changes in 6MWD or FTSTS. Conclusions The total volume and intensity of physical activity relative to an individual’s capacity, rather than bout length, may be key factors in counteracting short-term declines in physical functioning in older adults.