Oxygen utilization during loaded marching: The effect of external load on oxygen utilization during marching in Norwegian Army recruits

Abstract

Purpose: The purpose of this study was to investigate how external load affects oxygen uptake during submaximal exercise in male and female conscripts in the Norwegian Army, as well as exploring potential sex differences. Associations between physiological and anthropometrical variables and performance during submaximal exercise was also investigated.

Method: Testing was divided into test day 1 and test day 2. On test day 1, body composition (InBody 720), countermovement jump, 1RM bench pull, lactate threshold, anthropometric measurements, and V̇O2max were measured in 25 participants. On test day 2, an incremental 15-minute trial was conducted twice per participant, where the first was without rucksack, the second with rucksack. The 15-minute trial was divided into three 5-minute trials, the first beginning at 4 km·h-1, 5 km·h-1 and 6 km·h-1. 22 participants were tested on test day 2.

Results: The mean age in both sexes was 19,2 (±0,9) years. Mean weight was 75,3 (±7,8) kg, Fat percentage and fat mass were 13,5 (±4,9) % and 10,2 (±4,2) kg, respectively. Lean body mass and lean body mass index was 65,1 (±7,2) kg and 20,3 (±1,6), respectively. Mean muscle mass was 37,0 (±4,4) kg. Mean height was 178,9 (±6,1) cm, torso length and leg length was 45,72 (±2,1) cm and 85,78 (±4,2) cm, respectively. Mean jump height was 36,5 (±6,9) cm. Mean 1RM bench pull was 63,0 (±15,9) kg. Mean lactate threshold value was 6,5 (±2,0) mmol·l-1. Mean relative V̇O2max and absolute V̇O2max were 53,9 (±6,0) ml · kg-1 · min-1 and 4050 (±672,7) ml · min-1, respectively. In the first 15-minute trial on test day 2, mean V̇O2-uptake in men was 21,3 (±1,7), 25,6 (±2,7) and 32,3 (±3,3) ml · kg-1 · min-1 in 4, 5 and 6 km·h-1, respectively. It was 21,0 (±1,5), 26,4 (±1,5) and 32,7 (±1,3) ml · kg-1 · min-1 on 4, 5 and 6 km·h-1, respectively, in women. In the second 15-minute trial, mean V̇O2-uptake was 24,9 (±3,0), 32,5 (±2,7) and 41,8 (±3,4) ml · kg-1 · min-1 in 4, 5 and 6 km·h-1, respectively, in the men. In the women, mean V̇O2-uptake was 25,4 (±2,0), 32,0 (±2,8) and 41,7 (±2,9) ml · kg-1 · min-1 in 4, 5 and 6 km·h-1, respectively. In 5 km·h-1 during the first 15-minute trial, the average percent of V̇O2max was 44,5% (±5,5) and 53,0% (±4,6) in men and women, respectively. In 5 km·h-1 during the second 15-minute trial, the average percent of V̇O2max was 56,4% (±4,8) and 64,0% (±3,4) in men and women, respectively.

Conclusion: Marching with external load causes significant increases in oxygen uptake. There were no sex differences in marching without or with and external load. There were, however, significant sex differences in percent of V̇O2max (<0,005). Higher performance during submaximal exercise was associated with both absolute and relative V̇O2max, countermovement jump, 1RM bench pull, lactate threshold, height and lean body mass index.