Friend Social Network Size Moderates the Association Between Age and Physical Activity Across Adulthood.

Both physical activity and social network size decline as people age. However, limited research has examined if social network size and contact frequency differentially influence physical activity across the adult lifespan. This study aimed to assess if these social network characteristics moderated the relationship between age and physical activity level across adulthood. Multiple regression analyses were conducted to examine the main-effect association between age, past-week physical activity, and past-year physical activity, as well as the moderating effect of social network characteristics (i.e., friend network size, friend contact frequency, relative network size, and relative contact frequency) on age-physical activity associations. The results revealed that friend network size had moderated associations between age and past-week physical activity (β = -7.03; p = .025, f² = 0.13) and past-year physical activity (β = -585.52; p = .017, f² = 0.15). Specifically, adults who were older and had smaller friend networks performed more minutes of moderate-vigorous physical activity (MVPA) over the past week and past year; on the other hand, adults who were younger and had larger friend networks performed more minutes of MVPA over the past week and past year. Relative network size, friend contact frequency, and relative contact frequency did not moderate the relationship between age and past-week physical activity and past-year physical activity. These findings suggested that building friend networks throughout adulthood may help promote active living across the adult lifespan.