Objectives: This study aimed to investigate cross-lagged associations in motor competence, cardiorespiratory fitness, muscular fitness and accelerometer-based moderate-to-vigorous physical activity (MVPA) engagement.

Design: One-year prospective follow-up study.

Method: A sample was 491 (275 girls; M at baseline = 11.27, SD = .32) Finnish physical education students. Students’ motor competence was assessed by 1) two-legged jumping from side to side test, 2) throwing-catching combination test and 3) 5-leaps test. Their cardiorespiratory fitness was analyzed by a 20-meter shuttle run test and muscular fitness by curl-up and push-up tests. Additionally, students’ MVPA was measured objectively by hip-worn accelerometers.

Results: Results demonstrated that: 1) cardiorespiratory fitness measured at Grade 5 was the only significant predictor of later MVPA and this association appeared only in the boys’ group, 2) MVPA assessed at Grade 5 significantly predicted cardiorespiratory fitness in the girls’ group, 3) cardiorespiratory fitness collected at Grade 5 associated with muscular fitness, locomotor and stability skills in both girls and boys, and 4) locomotor skills measured at Grade 5 predicted significantly muscular fitness, locomotor and manipulative skills in both sex groups.

Conclusions: Elementary school years are important in providing students with experiences in physical activity (PA) which leads to improvements s in cardiorespiratory health. Additionally, this 25 study showed that cardiorespiratory fitness collected at Grade 5 associated with later muscular fitness, and locomotor and stability skills in both sex groups. These findings are noteworthy because muscular fitness in youth has several health-related benefits and motor competence in childhood and adolescence has positive association with later PA engagement.