Purpose: Background: Physical activity is a complex behavior
which involves the interaction of multilevel factors at the individual, social
and environmental level. However, previous studies have largely focused on
psychological and/or social environmental factors and the direct impact of
such factors on physical activity. There are few studies having examined how
multilevel factors may interact to influence activity level. Therefore, the
purpose of the present study was to examine both direct and indirect effects of
multilevel factors on school-based physical activity in Japanese adolescent
boys. Methods: In this cross-sectional survey of the Japanese adolescent
lifestyles, 379 junior high school boys were invited to complete self-report
measures of age, grade, weight, height, self-efficacy, social support (family,
friends and teachers), school physical environment (equipment, facilities and
safety) and average minutes per week of physical activity during lunch time
and after-school hours occurring at school. Structural equation modeling
analyses controlling for age were utilized to examine the effects of body
mass index (BMI), self-efficacy, social support and school physical environmental
variables on lunchtime and after-school physical activity. Results: During
lunch time, self-efficacy exhibited direct positive effects on physical
activity. BMI, facilities, and safety were indirectly associated with
lunchtime physical activity through self-efficacy. However, there were no
significant relationships of equipment and social support with lunchtime physical
activity. During after-school hours, family support and facilities directly
affected physical activity. Self-efficacy was indirectly related with
physical activity through family support. BMI, equipment, and safety indirectly
affected physical activity through self-efficacy and/or family support.
Conclusion: Effects of multilevel factor on physical activity among adolescent
boys differed according to context, which implies that interventions to
promote physical activity should be context-specific. Findings encourage
the development of future effective interventions to promote physical activity
through self-efficacy during lunch time as well as family support during
after-school hours.