Cardiorespiratory responses of load carriage in female and male soldiers

Abstract

Purpose: To investigate the effect of sex and load carriage on cardiorespiratory responses to high intensity exercise in male and female soldiers.

Methods: Soldiers (9 women, 9 men) performed a graded treadmill test until exhaustion with no load (NL) and combat-gear with body armor (CG). Cohen's d effect sizes, paired t-tests and ANOVA were used to study differences between conditions. A mixed linear regression model analyzed the relationship between heart rate (HR) and oxygen uptake (V̇O₂) with load and between sexes.

Results: Wearing CG resulted in, for both sexes, a decreased time to exhaustion (-11 min), lower V̇O_2peak (L/min) ES = 0.56; VO_2peak (mL//kg/min) ES = 2.44, both p < 0.001, a net decrease in minute ventilation (ES = 3.53) and no change in HR_max. No sex-difference were present except for absolute V̇O_2peak. The VO₂ and HR relationship showed a cardiorespiratory reduction wearing CG vs. NL. Added load was equal between sexes, although female soldiers' CG relative to body mass was higher (25%) than male soldiers' (20%), p < 0.01.

Conclusion: Wearing CG reduces soldiers' cardiorespiratory capacity and exercise performance level, although the reduction cannot be explained solely based on the added load of CG, instead CG seems to restrict the capacity to fully ventilate. No sex differences were found in relative cardiorespiratory responses to wearing CG compared to NL.

Keywords: Aerobic capacity; Graded exercise test; VO(2peak); Ventilation.