Using Motivational and Volitional Interventions to Promote Adolescents' Physical Activity

Background/Purpose: This study examined the impacts of the protection motivation theory (PMT)-based motivational intervention and implementation intentions-based volitional intervention on physical activity (PA) intention and behaviors between normal weight adolescents and overweight/obesity adolescents.

Method: A total of 335 junior high school adolescents were assigned to three groups: control group, motivational intervention group, and motivational and volitional intervention group. Motivational intervention (employed to both intervention groups at baseline) included reading a leaflet containing factual information about overweight/obesity and the effects of PA on preventing the health threat. Volitional intervention (added to motivational and volitional intervention group at the third week) involved asking participants planning when and where to exercise in the next 2 weeks. Adolescents' PMT constructs, PA intention and behaviors were measured at three time-points over a four-week period.

Analysis/Results: Two-way (intervention by weight) MANOVA with repeated measure yielded a nonsignificant main effect for intervention on PMT variables (F(12,648)=1.68, p>.05) and PA behaviors (F(2,329)=1.75, p>.05). However, there is a significant main effect for weight on PMT variables (F(6,324)=15.84, p<.01, η²=.23) and PA behaviors (F(1,329)=14.58, p<.01, η²=.04). Follow-up tests indicated overweight/obesity adolescents reported significantly higher perceived vulnerability, response costs than normal weight adolescents did (p<.05). They also reported significantly lower self-efficacy, intention, and PA behavior (p<.05).

Conclusions: The findings indicate that the interventions seemed not effective to promote PA intention and behaviors among adolescents. PA interventions for overweight/obesity adolescents should focus on enhancing their self-efficacy and reducing their perceptions of PA costs.