Physical exercise dose and bullying perpetration among middle school students: intervention effects and the mediating role of self-control

To examine whether experimentally assigned relative intervention doses were associated with changes in bullying perpetration and implicit attitudes toward bullying among middle school students, and to test whether self-control statistically mediated the association between habitual exercise dose and bullying behavior. Study 1 used a pretest-posttest controlled intervention design. Middle school students who engaged in bullying perpetration were screened and randomly assigned to a control group, a low-dose exercise group, or a medium-dose exercise group. Under a 12-week moderate-intensity soccer and physical fitness training program, the effects of experimentally assigned relative intervention doses, differentiated primarily by exercise frequency and session duration, on implicit attitudes toward bullying and total bullying behavior scores were compared. Study 2 used a cross-sectional survey to assess self-reported habitual exercise dose, self-control, and bullying behavior in 517 middle school students with bullying perpetration. After low- and medium-dose exercise, D scores for implicit attitudes toward bullying significantly increased and total bullying behavior scores significantly decreased; improvements were larger in the medium-dose group. Cross-sectional data showed that habitual exercise dose was positively correlated with self-control and negatively correlated with bullying behavior, whereas self-control was negatively correlated with bullying behavior. The bootstrap mediation model indicated a significant indirect effect of habitual exercise dose on bullying behavior through self-control, while the direct effect remained significant. In the 12-week moderate-intensity soccer and physical fitness training context examined here, more frequent and longer structured exercise was accompanied by improvements in bullying attitudes and total bullying behavior scores. Self-control may be a statistical explanatory variable linking habitual exercise dose with bullying behavior, although this mechanism requires further verification through longitudinal follow-up or experimental mediation designs. Schools may adopt moderate, regular, structured team sports as a low-stigma complementary pathway for bullying prevention and intervention.