Behavioral correlates of muscular fitness in children and adolescents: a systematic review

Background: Muscular fitness (MF) is considered a powerful marker of health, but the extent to which common health behaviors are associated with MF during childhood and adolescence is currently unclear. Objective: We conducted a systematic review of studies investigating associations between MF (i.e., strength/power, local muscular endurance) and physical activity, sedentary behaviors, and sleep in children and adolescents. Methods: A systematic search of six electronic databases was performed on 8 March, 2017. Search results were screened for relevance and studies conducted with children and adolescents (3–18 years) that explored associations between MF and physical activity, sedentary behavior, or sleep were considered eligible. Data were extracted and checked by a second author. The proportion of studies reporting a statistically significant association between each MF component and behavioral variables was calculated, and additional coding was conducted to account for risk of bias. Results: There was consistent evidence for a positive association between MF and physical activity. For both MF components, there was support for objectively measured physical activity, particularly for activity of vigorous intensity. Sports participation was also consistently linked with both MF components, whereas the association with active transport was inconsistent. For both MF components, associations with sedentary behaviors were inconsistent irrespective of measurement method, and the association between MF and sleep was considered uncertain. Conclusions: The available evidence supports a link between MF and physical activity, particularly for vigorous intensity activity and organized sports participation. Conversely, there is limited support for an association with sedentary behaviors, and more research exploring MF and sleep is required.