Accuracy of Metabolic Cost Predictive Equations during Military Load Carriage

To quantify the accuracy of five equations to predict the metabolic cost of load carriage under ecologically valid military speed and load combinations. Thirty-nine male serving infantry soldiers completed thirteen, 20-minute bouts of overground load carriage comprising of two speeds (2.5 and 4.8 km·h-1) and six carried equipment load combinations (25, 30, 40, 50, 60, and 70 kg), with 22 also completing a bout at 5.5 km·h-1 carrying 40 kg. For each speed-load combination the metabolic cost was measured using the Douglas bag technique, and compared to the metabolic cost predicted from five equations; Givoni & Goldman, 1971 (GG), Pandolf et al. 1997 (PAN), Santee et al. 2001 (SAN), American College of Sports Medicine 2013 (ACSM), and the Minimum-Mechanics Model (MMM), Ludlow & Weyand, 2017. Comparisons between measured and predicted metabolic cost were made using repeated measures ANOVA and Limits of Agreement. All predictive equations, except for PAN, under-predicted the metabolic cost for all speed-load combinations (p<0.001). The PAN equation accurately predicted metabolic cost for 40 and 50 kg at 4.8 km·h-1 (p>0.05), under-predicted metabolic cost for all 2.5 km·h-1 speed-load combinations as well as 25 and 30 kg at 4.8 km·h-1, and over-predicted metabolic cost for 60 and 70 kg at 4.8 km·h-1 (p<0.001). Most equations (GG, SAN, ACSM, MMM) under-predicted metabolic cost while one (PAN) accurately predicted at moderate loads and speeds, but over-predicted or under-predicted at other speed-load combinations, indicating that caution should be applied when utilising these predictive equations to model military load carriage tasks.