Sex differences in the physiological response to a demanding military field exercise.

Purpose: To investigate sex differences in the effect of a military field exercise on physical performance, body composition, and blood biomarkers.

Methods: Measurements were done in 23 male and 12 female conscripts before, and 0, 1, 3, 7, and 14 days after a 6-day military field exercise.

Results: During the field exercise, body mass decreased more in men (-6.5 ± 1.1 kg) than in women (-2.7 ± 0.7 kg), and muscle mass decreased only in men (-2.7 ± 1.0 kg). Body composition recovered within one week. Performance decreased, with no differences between men and women for countermovement jump (CMJ,-19 ± 8 vs. -18 ± 11%), medicine ball throw (MBT, -11 ± 7 vs. -11 ± 7%), and an anaerobic performance test (EVAC, -55 ± 22 vs. -47 ± 31%, men and women, respectively). MBT and EVAC performance recovered within two weeks, whereas CMJ performance was still reduced in men (-17 ± 6%) and women (-9 ± 8%) after two weeks recovery, with a larger reduction in men. Both men and women decreased [IGF-1] (-28 ± 9 vs. -41 ± 8%) and increased [cortisol] (26 ± 26 vs. 66 ± 93%, men and women, respectively) during the exercise. Most biomarkers returned to baseline values within one week.

Conclusions: Men lost more body mass and muscle mass than women during a field exercise, but these differences did not lead to sex differences in changes in explosive strength and anaerobic performance. However, women recovered explosive strength in the legs faster than men.