RESUMEN
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.
RESUMEN
Maximal oxygen uptake (VO2max) is an important, independent predictor of cardiovascular health and mortality. Despite this, it is rarely measured in clinical practice. The aim of this study was to create and evaluate a submaximal cycle ergometry test based on change in heart rate (HR) between a lower standard work rate and an individually chosen higher work rate. In a mixed population (n = 143) with regard to sex (55% women), age (21-65 years), and activity status (inactive to highly active), a model included change in HR per unit change in power, sex, and age for the best estimate of VO2max. The association between estimated and observed VO2max for the mixed sample was r = 0.91, standard error of estimate = 0.302 L/min, and mean measured VO2max = 3.23 L/min. The corresponding coefficient of variation was 9.3%, a significantly improved precision compared with one of the most commonly used submaximal exercise tests, the Åstrand test, which in the present study was estimated to be 18.1%. Test-retest reliability analysis over 1 week revealed no mean difference in the estimated VO2max (-0.02 L/min, 95% confidence interval: -0.07-0.03). The new test is low-risk, easily administered, and valid for a wide capacity range, and is therefore suitable in situations as health evaluations in the general population.