4.2. Limitations
Unlike many previously published studies, this investigation incorporated well-validated objective and subjective MVPA measures on the same children. However, while it demonstrated several strengths such as this, the current study was also not without its limitations. For one, the study was cross-sectional in design, which does not permit causal conclusions. Selection bias is a possibility as the study sample was based on geographical convenience. The sample size was also smaller than desired to facilitate generalizability, although similar studies have reported using similar sizes.12 A potential Hawthorne effect (observational bias as a result of being watched) may have also occurred, as students were pulled from class in small groups to answer questionnaires. Questionnaires were completed the week before the accelerometers were worn, and accelerometers could not be worn while swimming, indicating potential measurement biases. This study either did not examine an exhaustive list of psychosocial variables that have been identified previously. While measuring a more extensive list would be preferable (e.g., perceived social support, task goal orientation, perceived accessibility, etc.), schools have a limited amount of available time and further burdening the teachers and students would have been detrimental to the study. Lastly, a convenience sample of middle schools was used, with geographical differences between groups. While the literature indicates that children living in more rural environments are more physically active, 26 emerging research also suggests a geographical and seasonal relationship in which urban children have been shown to be significantly more active in the winter compared to rural children, but significantly less active in the summer. 27 Therefore, future studies should consider the impact of seasons and the built environment (perceived and objective) in regards to objective and subjective PA.
4.2. LimitationsUnlike many previously published studies, this investigation incorporated well-validated objective and subjective MVPA measures on the same children. However, while it demonstrated several strengths such as this, the current study was also not without its limitations. For one, the study was cross-sectional in design, which does not permit causal conclusions. Selection bias is a possibility as the study sample was based on geographical convenience. The sample size was also smaller than desired to facilitate generalizability, although similar studies have reported using similar sizes.12 A potential Hawthorne effect (observational bias as a result of being watched) may have also occurred, as students were pulled from class in small groups to answer questionnaires. Questionnaires were completed the week before the accelerometers were worn, and accelerometers could not be worn while swimming, indicating potential measurement biases. This study either did not examine an exhaustive list of psychosocial variables that have been identified previously. While measuring a more extensive list would be preferable (e.g., perceived social support, task goal orientation, perceived accessibility, etc.), schools have a limited amount of available time and further burdening the teachers and students would have been detrimental to the study. Lastly, a convenience sample of middle schools was used, with geographical differences between groups. While the literature indicates that children living in more rural environments are more physically active, 26 emerging research also suggests a geographical and seasonal relationship in which urban children have been shown to be significantly more active in the winter compared to rural children, but significantly less active in the summer. 27 Therefore, future studies should consider the impact of seasons and the built environment (perceived and objective) in regards to objective and subjective PA.
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