Association between college students 'physical fitness index and negative emotional symptoms: an empirical study based on college students in Chongqing City, China

Objectives To investigate the independent associations between the physical fitness index (PFI), as well as individual physical fitness metrics, and negative emotional symptoms (stress, anxiety, and depression) among college students; and to analyze gender-specific variations in these associations, thereby providing empirical, fitness-based evidence for mental health interventions in higher education institutions. Methods Utilizing a cross-sectional design, this study selected 2,190 college students from 73 universities across Chongqing via stratified cluster sampling. A standardized physical fitness test battery—comprising vital capacity, the 50-meter sprint, the 800/1000-meter run, the sit-and-reach test, and pull-ups/sit-ups—was administered to calculate the comprehensive PFI. Negative emotional symptoms were assessed using the 21-item Depression Anxiety Stress Scales (DASS-21). Multivariable Logistic regression models were employed to evaluate the independent associations between physical fitness and negative emotional symptoms, after comprehensively adjusting for moderate-to-vigorous physical activity (MVPA), muscle-strengthening exercise (MSE), screen time, sedentary duration, and sociodemographic variables. Results The detection rates of stress, anxiety, and depression symptoms were 68.08%, 67.67%, and 12.37%, respectively. In conventional categorical models, moderate and high PFI were associated with lower odds of all three outcomes in the pooled sample, although several high-PFI estimates were extremely small. Firth sensitivity analyses supported inverse associations for high PFI across outcomes and sexes; however, moderate PFI was not statistically associated with stress in female students or anxiety in male students. Continuous PFI analyses showed lower odds of each outcome per 1-SD increase in the pooled and sex-stratified samples (all P < 0.001). These patterns were broadly consistent with the individual-component analyses, but the cross-sectional design precludes causal interpretation. Conclusions Higher PFI was independently associated with lower odds of negative emotional symptoms among college students. The consistency of direction across categorical, Firth-penalized, and continuous-PFI models supports the robustness of the association, but the extreme categorical estimates, model-calibration findings, sample-relative cutoffs, and cross-sectional design require cautious interpretation. Longitudinal and intervention studies are needed before PFI is used as a clinical or campus screening threshold.