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Explaining the effects of a 1-year intervention promoting physical activity in middle schools: a mediation analysis

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journal contribution
posted on 2008-05-01, 00:00 authored by L Haerens, Ester Cerin, L Maes, G Cardon, B Deforche, I De Bourdeaudhuij
Objective : The aim of the present study was to examine the mediation effects of changes in psychosocial determinants of physical activity (attitude, social support, self-efficacy, perceived benefits and barriers) on changes in physical activity.

Design : One-year intervention study with baseline and 1-year post measures of physical activity habits and psychosocial correlates.

Setting : Fifteen middle schools. Subjects : Boys and girls (n = 2840) aged 11–15 years completed the validated questionnaires during class hours.

Results : The product-of-coefficients test was used to asses the mediating effects. Self-efficacy for physical activity at school was found to be the only significant mediator of physical activity change. Specifically, self-efficacy for physical activity at school partly mediated the effect of the intervention on total and school-related physical activity change in the intervention group with parental support (P < 0.05). None of the other potential mediators, attitudes, social support, perceived benefits and perceived barriers, seemed to have had a positive effect. Even a suppressor effect was found for attitudes. Given that the effects of self-efficacy and attitudes were of opposite direction, the total mediated/suppressed effects of the intervention were not statistically significant.

Conclusions : Positive changes in total and school-related physical activity in adolescents could be partly explained by increases in self-efficacy for physical activity at school through a physical activity intervention in middle schools with parental support. However, the suppressor effect of attitudes decreased this effect. As this is one of the first true mediation analyses in this age group, further research is needed to replicate the importance of these mediators.

History

Journal

Public health nutrition

Volume

11

Issue

5

Pagination

501 - 512

Publisher

Cambridge University Press

Location

Cambridge, England

ISSN

1368-9800

Language

eng

Publication classification

C1.1 Refereed article in a scholarly journal

Copyright notice

2008, Cambridge University Press

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