Metabolic Responses of South African Soldiers during Simulated Marching with 16 Combinations of Speed and Backpack Load

Abstract

This study assessed the metabolic responses of South African soldiers marching at different speeds and carrying varying loads. The main objective was to establish the physiological cost of a range of speed/load combinations to identify the energy requirements to meet a diversity of march objectives. Thirty male soldiers marched on a treadmill for 6 minutes with varying combinations of speed and load, established through numerous pilot studies and in consultation with military personnel. The four speeds were 3.5, 4.5, 5.5, and 6.5 km x (-1), combined with the four loads of 20, 35, 50, and 65 kg, totaling 16 combinations. Each participant completed eight of the 16 conditions, during which the participants wore standardized military gear and were attached to a portable ergospirometer (the Metamax, Cortex, Leipzig, Germany) for the duration of the march. Based on the responses, five discrete categories of speed/load combinations were identified. These combinations were categorized as nominal (< 40% of maximal oxygen consumption [VO(2max)]), moderate (40-50% of VO(2max)), heavy (50-65% of VO(2max)), very heavy (65-80% of VO(2max)), and excessive (> 80% of VO(2max)), with each categorization incorporating diverse combinations of speed and load. The findings demonstrate that the interplay between marching speed and backpack load plays a crucial role in ensuring that similar metabolic demands are maintained at a bearable level to meet specific military circumstances, thus reducing the likelihood of injuries and the early onset of fatigue and ensuring that the soldiers are combat ready on arrival at their destination.