Cardiorespiratory responses induced by various military field tasks

Typical military tasks include load carriage, digging, and lifting loads. To avoid accumulation of fatigue, it is important to know the energy expenditure of soldiers during such tasks. The purpose of this study was to measure cardiorespiratory responses during military tasks in field conditions. Unloaded (M1) and loaded (M2) marching, artillery field preparation (AFP), and digging of defensive positions (D) were monitored. 15 conscripts carried additional weight of military outfit (5.4 kg) during M1, AFP, and D and during M2 full combat gear (24.4 kg). Absolute and relative oxygen uptake (VO2) and heart rate (HR) of M1 (n = 8) were 1.5 ± 0.1 L min(-1), 19.9 ± 2.7 mL kg(-1) min(-1) (42 ± 7% VO2max), and 107 ± 8 beats min(-1) (55 ± 3% HRmax), respectively. VO2 of M2 (n = 8) was 1.7 ± 0.2 L min(-1), 22.7 ± 3.4 mL kg(-1) min(-1) (47 ± 6% VO2max) and HR 123 ± 9 beats min(-1) (64 ± 4% HRmax). VO2 of AFP (n = 5) and D (n = 6) were 1.3 ± 0.3 L min(-1), 18.0 ± 3.0 (37 ± 6% VO2max), and 1.8 ± 0.4 L min(-1), 24.3 ± 5.1 mL kg(-1) min(-1) (51 ± 9% VO2max), respectively. Corresponding HR values were 99 ± 8 beats min(-1) (50 ± 3% HRmax) and 132 ± 10 beats min(-1) (68 ± 4% HRmax), respectively. The mean work intensity of soldiers was close to 50% of their maximal aerobic capacity, which has been suggested to be maximal limit of intensity for sustained work.