The moderating role of cardiorespiratory fitness in adolescents' physiological and psychological responses to real-life academic stress

The influence of physical activity and cardiorespiratory fitness (CRF) on physiological/psychological stress reactivity has been a longstanding focus of scientific research. However, it remains unclear whether laboratory-based research extends to real-life stressors. We therefore examined whether CRF moderates physiological/psychological stress reactivity in adolescents during a real-life stress situation. The study was conducted with 79 ninth-grade students (M=14.19±0.79 years; 49.4% girls). Physiological stress response was assessed via heart rate (HR) and heart rate variability (HRV), measured during a mathematics exam (stress condition) and a regular mathematics lesson (baseline condition). HRV was indexed using low frequency power (LF). Psychological responses (affective states, anxiety) were evaluated through standardized self-report questionnaires. CRF was estimated using the 20-meter Shuttle run test, and participants were categorized into low vs. high fitness groups via median split. Differences in stress reactivity were tested via repeated-measures ANOVAs. Statistically significant condition-by-group interactions were observed for affective states and anxiety. While no significant group differences emerged at baseline, participants with higher estimated CRF exhibited more positive affective states and lower anxiety during the stress condition. Furthermore, the high fitness group demonstrated lower HR and higher HRV at baseline and during the stress condition. Higher estimated CRF is associated with more favorable autonomic functioning and reduced psychological stress reactivity in adolescents facing a real-life stressor. These findings suggest that students with higher estimated CRF may be better equipped to cope with everyday stressors. Promoting CRF in youth may represent a viable strategy to support psychological and physiological health. • Exposure to a mathematics exam is associated with increased physiological and psychological stress. • During stress, higher cardiorespiratory fitness (CRF) is associated with lower stress levels. • Students with higher CRF present with better heart rate, heart rate variability, anxiety and mood. • A statistically significant interaction between condition and CRF only exists for psychological outcomes. • More effective coping may explain why children with higher CRF perform better in school.