A cluster analysis of physical activity and sedentary behavior patterns in middle school girls

To identify similar patterns of physical activity (PA) and sedentary behavior in sixth-grade girls using cluster analysis; to determine which clusters of girls were associated with greater daily minutes of objectively measured PA; and to examine whether girls in these clusters experienced change in PA from sixth to eighth grade.

An adventitious cohort of girls (n = 957) from the Trial of Activity for Adolescent Girls were measured at sixth and eighth grade. Activities were identified using the 3-day physical activity recall and a self-report survey and used to create clusters of sixth-grade girls who had similar PA/sedentary behaviors. Accelerometry was used to assess PA in sixth and eighth grade. Data analysis consisted of FASTCLUS procedure and mixed model repeated measures analyses in SAS statistical software.

Cluster analysis yielded six clusters (C1: educational sedentary; C2: sports and play; C3: organized sports teams/classes/lessons in past year; C4: active transport and chores; C5: electronic media; C6: sleep). Sixth-grade girls in C2 and C3 had greater average daily minutes of moderate-to-vigorous physical activity (MVPA), metabolic equivalent of a physical activity-weighted MVPA, and vigorous physical activity compared with other clusters (p < .05). In eighth grade, sedentary time increased and PA declined among girls in all clusters (p < .05). Girls in C2 had the greatest decline in PA, whereas girls' PA in C3 declined less.

Encouraging participation in organized sports teams/class/lessons in middle school girls may promote greater MVPA and vigorous physical activity than other activities and may help to better sustain PA levels over time.