Gymnastik- och idrottshögskolan, GIH

INTRODUCTION: Military operations place high demands on many cognitive functions, and stressful events characterise the military work environment. The study aimed to examine the relationship between cardiorespiratory fitness, stress response, cognitive function and military performance during prolonged military exercise.

METHODS: 66 army cadets were included in the study. The subjects participated in a 4.5-day military winter training in northern Sweden. Maximal oxygen uptake (VO₂max) was estimated from a cycle test. Cognitive tests (design fluency, DF test) and measurements of heart rate variability (HRV) were conducted before and after the exercise. Assessment of military performance as an individual soldier (P-ind) and performance as a team leader (P-lead) was carried out during the final day of the exercise. Pearson's coefficient of correlation (r) and Spearman's rho were used to evaluate correlations, and linear regressions were used to examine the relationships between VO₂max, HRV, DF test scores and military performance. Simple mediation analyses were performed with DF test scores and military performance (P-ind, P-lead) as dependent variables, VO₂max as a predictor and HRV as a mediator.

RESULTS: Post-exercise HRV was related to military performance (P-ind: r=0.40, p<0.01; P-lead: r=0.32, p<0.05). Absolute VO₂max was positively correlated with P-ind (r=0.28, p<0.05), and the effect of VO₂max on military performance was mediated by HRV. Post-test DF scores were negatively correlated with post-exercise HRV (total correct designs: r=-0.26, p<0.05; total incorrect designs: r=-0.27, p<0.05).

CONCLUSIONS: Results suggest that high absolute VO₂max predicts military performance by reducing the stress response to prolonged military exercise. Aerobic capacity may provide a meaningful effect on the ability to preserve military performance. Future studies need to identify thresholds for this capacity.

PRE-REGISTRATION: The protocol was retrospectively registered at OSF (https://osf.io/), registration DOI 10.17605/OSF.IO/ND6XM.