Effects of modern military footwear on the oxygen costs of walking in US Army personnel

Warfighters complete strenuous physical activity on their feet throughout their military careers. While greater physiologic costs of walking have been demonstrated with older models of military combat boots versus running shoes, these quantitative differences may not be applicable for contemporary military footwear. The purpose of this study was to quantify and compare physiological responses to walking when wearing modern military combat boots versus running shoes. In this randomized, counterbalanced crossover experiment, 34 active military personnel (29 men and 5 women; age, 26 ± 7 years; height, 1.74 ± 0.08 m; body mass, 77.9 ± 15.1 kg) completed an incremental walking test (4.18–7.08 km^.h⁻¹) on separate visits in running shoes (mass, 0.6 ± 0.1 kg) and military combat boots (mass, 1.2 ± 0.3 kg). Oxygen uptake (V̇O₂), carbon dioxide production (V̇CO₂), heart rate (HR), respiration rate (RR), and metabolic energy expenditure (Ṁ) measurements were collected and averaged over the final minute of each walking speed. The oxygen costs of walking were 6–9% higher when wearing combat boots versus running shoes (p < 0.01 for each comparison). Other cardiorespiratory indicators of exercise intensity, specifically V̇CO_2, Ṁ, HR, and RR, increased by 2.7–9.9% (p < 0.02 for each indicator). Walking in modern military combat boots incurs noticeably increased metabolic and cardiorespiratory strain as compared to walking in running shoes. These physiological consequences emphasize the trade-off between the intended versatility and protective characteristics of military footwear and the economy of traditional running shoes. This strain must be considered when selecting footwear to maximize warfighter health and performance during military exercise interventions.