Data analysis
The data analysis was conducted using JASP (Version 0.17.1; University of Amsterdam, Amsterdam, the Netherlands). Asymmetry values between -2 and + 2 and kurtosis values between -7 and + 7 were considered indicative of the data being normally distributed [Randomization check to examine the baseline differences between study groups and attrition check to examine the differences between those who remain in the study and those who are lost to follow-up were conducted by using the independent samples In the main analysis, a series of repeated-measures ANOVAs were used to test the effectiveness of the web-based need-supportive parenting program on the dependent variables (perceptions of parents’ need-supportive behaviours, basic psychological need satisfaction and frustration, autonomous and controlled forms of motivation, social cognition beliefs towards leisure-time PA and self-reported PA). Intervention condition (intervention vs control) was used as a between-subject factor and time (baseline vs post-intervention vs one-month follow-up) was used as a within-subject factor in each of the repeated measures ANOVAs. A post hoc analysis, independent measures 