The health benefits of habitual physical activity (PA) in youth are well-established through several sources of research. Despite the known benefits, surveillance studies at the population level suggest that less than one-quarter (24%) of youth 6 to 17 years of age participate in 60 minutes of physical activity every day. Additionally, previous literature has shown that PA behaviors developed as a child may track into adulthood. Taken together, these facts highlight the importance of examining children’s (6–11 yrs.) and adolescents’ (12–17 yrs.) PA and studying different PA promotion strategies in greater depth to determine how, when and where children are being active or are more likely to be active. By doing so, researchers may be able to effectively promote PA in youth moving forward, and help children develop healthy lifestyle habits early so that they can take these habits with them into adulthood. The majority of the existing literature on PA focuses on time spent in specific PA intensity levels (light, moderate, or vigorous), or simply on total daily PA, with very little research examining the temporal patterns of PA. Evaluating temporal patterns of PA supports the notion that all people, youth included, may follow distinct patterns in their PA within a day and/or over the course of the days, weeks, months, and seasons. Therefore, the purpose of this dissertation is twofold. First, to identify and summarize the existing literature on temporal patterns of PA in youth, and second, to make suggestions for future research to identify optimal times to improve PA promotion strategies and eventually, the overall health of our youth. This dissertation is comprised of three separate manuscripts. Manuscript 1 is a systematic literature review to examine and summarize all aspects of temporal patterns in youth PA. Patterns examined in this review included within-day PA (n=13; 43.3%), day-to-day PA (n=7; 22.5%), longitudinal PA (n=2; 6.7%), weekday PA only (n=2;6.7%), weekday vs. weekend PA (n=15; 30%), PA Compensation (n=12; 40%), and PA Synergy (n=3; 10%). Findings suggest that studies examining the temporal patterns of PA in youth have largely varying results (age, sex, setting etc.). Manuscript 2 is a study which aimed to identify temporal patterns during the school day and participant characteristics that may be associated with higher levels of PA in a PA intervention in girls from urban, low SES areas with a high percentage of racial/ethnic minorities during a PA intervention. Kendall’s tau revealed significant correlations (p<0.001) for average MVPA min/hr between all four time periods, with the strongest correlation occurring between after-school and evening time periods (ƭ=0.563, p<0.001), Results showed that girls’ PA levels, in general, rose and fell throughout the day, while girls who were more active relative to their peers remained more active and those who were relatively inactive stayed inactive. Manuscript 3 is a study which examined PA during an after-school program to identify patterns and predictive participant characteristics of PA behavior. Results showed that every minute increase in average afterschool moderate-to-vigorous PA (MVPA) min/hr at baseline was associated with a corresponding additional 3.90 minutes of MVPA min/hr during the PA club (ß=3.90 ± 0.31, p<0.001). No participant characteristics were found to be predictive of PA behavior. This dissertation underscores the need for a better understanding of temporal patterns, provides insight into how the school day structure is a driving force in the activity level of youth, and highlights the need for appropriate promotional strategies and innovative school-based interventions to increase overall PA levels, with the end goal being to help children become healthy, active adults.
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