Longitudinal changes in the structure of moderate and vigorous physical activity across adolescence for females

Abstract

Introduction: In an effort to curb rising levels of overweight and obesity, much attention has been given to understanding physical activity (PA) levels, in particular for adolescent females. Whilst general trends are often reported, it is important to understand the specific contexts of participation and how they may change over time. This studywas aimed at investigating changes in the contexts of moderate and vigorous physical activity (MVPA) for adolescent females, from Year 7 to post-secondary school. Methods: A 3-year longitudinal survey was conducted with females recruited in either Year 7 or Year 11. The questionnaire gathered demographic details, information about determinants of PA and PA outcome measures, including a Previous Day Physical Activity Recall (PDPAR) diary, from which self-reported total time spent in MVPA was calculated. An integrated cross-sectional and longitudinal analysis was conducted to investigate the duration and proportion of MVPA time occurring in the categories of sport, other (non-sport) PA and active transport, at six Year levels (7–9 and 11–13). Results: Analysis was based on participants who completed the relevant questions (n=Year 7: 381; Year 11: 211). The mean 24-hour total duration of MVPA increased significantly from Year 7 (mean±95% confidence interval: 45.8±8.0min) to Year 9 (65.5±8.5min) but the difference between the mean duration in Year 7 and the mean duration in Year 13 (53.1±14.1min) was not significant. There were, however, significant changes across time with respect to the form of MVPA undertaken. In Year 7, the mean proportion ofMVPA time associatedwith sport (59.2±7.8 percent) was significantly greater than themean proportion associatedwith other PA (35.7±7.8 percent), whereas for each of Years 12 and 13, the mean proportion of MVPA time associated with other PA (62.6±9.7 percent; 66.6±13.3 percent) was significantly greater than themeanproportionassociatedwith sport (34.0±9.7percent; 28.1±13.2 percent). The mean proportion of MVPA time undertaken in the form of active transport did not change significantly over time. Discussion: It is pleasing to see that total time spent in MVPA by this sample of adolescent girls did not significantly decrease over time.However, the context of participationdid change significantly over time, with sport playing a larger role than other PA in early adolescence and this role reversing during late adolescence. The sport sector could benefit from understanding why this transfer occurs, and perhaps reverse this trend by offering more genderand age-appropriate programs.