Dose-response associations between physical fitness components and anxiety in Chinese university students: A focus on cardiorespiratory fitness and vital capacity

Despite the mental health benefits of physical activity, the specific dose-response relationship between objectively measured physical fitness (especially cardiorespiratory fitness and lung capacity) and anxiety in youth is unclear. The purpose of this study is to explore the association between these indicators in Chinese college students. A cross-sectional analysis of 3878 undergraduate students was conducted. Anxiety was assessed using the generalized anxiety disorder 7-item scale (a score of ≥10 was positive). Objective measurement of cardiopulmonary function, muscle strength, flexibility and vital capacity, and according to national standards, excellent, good, pass, fail 4 grades. After controlling for demographics and health behaviors, adjusted odds ratios (aOR) and 95% confidence intervals (CIs) for anxiety were calculated by multivariate logistic regression and analyzed graphically. The prevalence of anxiety was 24.9%. Cardiopulmonary function and muscle strength showed a clear negative dose-response relationship: compared with the excellent grade, the failing grade had the highest cardiopulmonary function related anxiety ratio (aOR = 2.15, 95% CI: 1.50-3.08), followed by muscle strength (aOR = 1.75, 95% CI: 1.18-2.60). There was a significant nonlinear association between spirometry and anxiety, with only a significantly higher risk of passing grade (aOR = 1.85, 95% CI: 1.35-2.53). Comprehensive effect analysis showed that students who failed both heart, lung and muscle had the highest risk. Among the behavioral factors, poor sleep quality (aOR = 2.85) and frequent staying up late (aOR = 1.65) were most strongly associated with anxiety. This study demonstrates a significant negative dose-response association between higher levels of cardiorespiratory fitness and muscle strength and lower odds of anxiety in college students, while vital capacity shows a complex nonlinear relationship. Improving these physical fitness components may be a feasible strategy associated with lower anxiety risk, although causality cannot be inferred from the cross-sectional design.