Longitudinal Associations of Physical Activity Among Females from Adolescence to Young Adulthood.

Purpose: We sought to identify individual, social, and environmental factors associated with moderate-to-vigorous physical activity (MVPA) among females from ages 14 to 23years.

Methods: A cohort was formed from females originally participating in the Trial of Activity for Adolescent Girls Maryland site. The cohort was recruited from a randomly generated list of eighth grade girls in participating middle schools. A total of 428 females had complete assessments in 2006 (n = 730), 2009 (n = 589), and 2015 (n = 460). The outcome, MVPA, was assessed from accelerometers. Individual and social factors were assessed by questionnaire; body mass index was measured in 2006 and 2009 and self-reported in 2015. Perceived environment was assessed by questionnaire; number of parks near home and distance to parks and schools was assessed by geographic information systems.

Results: Participants were diverse (45.7% white, 24.8% black, 9.9% Hispanic, and 19.6% other). Over time 274 participants had continuously low MVPA, 123 decreased MVPA from age 17 to 23years, and 31 participants continuously increased MVPA. For each .16-unit decrease in body mass index, MVPA increased 1 minute over time (p = .007). For every 1-unit increase in self-management strategies or social support from friends, there was a 4- to 5-minute increase in MVPA (p < .0001 and p = .03, respectively). A little less than one extra park (.71 parks) within a mile of an individual's home was associated with a 1-minute increase in MVPA (p < .0001).

Conclusions: Behavioral strategies combined with neighborhood enhancements may produce the best results for increasing MVPA as adolescent females' transition into adulthood.