Associations Between Cardiorespiratory Fitness and Endocrine, Autonomous and Psychological Stress Reactivity in Male Adolescents

High stress burden during adolescence can have severe long-term health consequences. While some studies reported that adults with higher fitness levels show lower stress reactivity, research on adolescents is scarce. Accordingly, the aim of the present study was to investigate the association between cardiorespiratory fitness and physiological and psychological stress reactivity in male adolescents. Forty-three healthy, male adolescents aged 16-20 years underwent the Physical Working Capacity 170 bicycle ergometer test to determine cardiorespiratory fitness. The Trier Social Stress Test (TSST) was used to trigger a stress reaction, which was measured physiologically with changes in salivary cortisol and alpha-amylase concentrations, and psychologically using self-rated changes in state-anxiety. Under consideration of potential confounders, hierarchical regression analyses were calculated for each outcome. For cortisol and psychological stress reactivity, fitness did not significantly explain variance. However, 28% of variance in alpha-amylase reactivity were explained by fitness and sleep complaints [adjusted R2 = .28, F(2, 36) = 8.36, p = .001], with 16% of variance explained by fitness alone (β = −.41, p = .006). Accordingly, higher fitness was associated with lower stress reactivity of the autonomous nervous system in male adolescents. The promotion of cardiorespiratory fitness may therefore be considered an important factor in preventing negative health consequences of stress in this age group.