The Influence of High School Physical Education Curriculum Design Based on Self‐Determination Theory on Students' Intrinsic Motivation

- Intrinsic motivation improvement: The experimental group showed a significant increase in intrinsic motivation levels, with an effect size of 1.28 standard deviations (d = 1.28), which was significantly higher than that of the control group. - Core needs satisfaction: There were graded differences in the enhancement of the three core needs among the experimental group: autonomy needs (d = 1.12), competence needs (d = 0.95), and relatedness needs (d = 0.83). These three factors drove the internalization of students' intrinsic motivation through a full mediating effect, accounting for 87% of the total variation in motivation improvement. - Cross-group difference (moderation effect): From the perspective of gender difference, girls in the experimental group had a more significant increase in relatedness needs satisfaction (mean difference = 0.22, p 〈 0.05); in terms of exercise foundation, the motivation improvement of students with low exercise foundation was twice that of those with high exercise foundation (B = 0.45 vs. 0.22). - Spillover effects and academic impact: The curriculum intervention produced significant positive spillover effects: the weekly extracurricular exercise time of the experimental group increased from 2.1 hours to 3.4 hours (p 〈 0.001), and the sports injury rate decreased by 62% (odds ratio OR = 0.38). Meanwhile, the intervention had no significant interference with students' academic performance (η² 〈 0.01).