Association of Physical Activity and Gait Speed: Does Context Matter?

Background: Physical activity (PA) is associated with gait speed, and both are recognized predictors of important health outcomes. The role of social context, such as PA of one's spouse, in the association between PA and gait speed is largely unexplored. Methods: In our dyadic study of 69 couples, we objectively assessed each partner's moderate to vigorous PA (MVPA) and gait speed. Associations of MVPA and gait speed were tested using actor-partner interdependence models in a structural equation modeling framework. Whether partners' typically exercise together was examined as a moderator of these associations. Results: A nonlinear association was observed where higher MVPA was associated with faster gait speed, but only when MVPA was below average (husbands β = -.517; P = .002; wives β = -.483; P = .009). No moderating effects of exercising together were detected for husbands' or wives' MVPA on their own or their partners' gait speed. Conclusions: In this investigation of couples, the association between MVPA and gait speed emerged only when nonlinear effects were considered. Findings suggest that the PA and gait speed association may be more nuanced than previously examined. Additional consideration of contextual factors that may alter the complex association between MVPA and gait speed is warranted.