Conclusions
This study tested an online need-supportive training for parents to enhance children's leisure-time physical activity and autonomous motivation. There was a positive trend in vigorous and total MET-minutes per week for children in the intervention group, but no statistically significant intervention effect. However, the parents' training resulted in lower perceptions of introjected regulation and autonomy frustration in children, indicating the development of more autonomous forms of motivation towards leisure-time PA in children. These findings suggest that while the parent’s need-supportive training may not have a significant impact on physical activity, it can increase children's intrinsic motivation and reduce controlled forms of motivation. Future research should aim to address the limitations of the current study, including the use of objective measures of physical activity and recruiting larger sample sizes. To improve the generalizability of the findings, future research could test the intervention in other domains beyond leisure-time PA, such as school PE lessons.