Predicting Metabolic Costs Of Heavy Backpacking

Abstract

The US Army Load Carriage Decision Aid (LCDA) is a planning tool composed of biomedical models that predict Warfighter physiological responses during dismounted operations. The LCDA’s metabolic model requires new equations to accurately predict the added metabolic cost of carrying varying types and amounts of military equipment. PURPOSE: Develop an equation for the LCDA metabolic model that better predicts the metabolic costs of carrying backpack loads. METHODS: Thirteen studies in which volunteers walked while carrying heavy pack loads were obtained for analysis. Treadmill speeds ranged between 1.1 - 1.8 m·s-1 with maximum pack loads exceeding 55% body mass. We used k-fold cross-validation to test how well the new model generalized to new data. Equivalence of predicted and measured metabolic rates was tested using the two one-sided t-test (TOST). We compared the new backpacking equation’s accuracy against the LCDA graded walking equation using the Concordance Correlation Coefficient (CCC). RESULTS: Predictions from the LCDA metabolic model were statistically equivalent to metabolic rates measurements during each step of the k-fold cross-validation (p < 0.05). Predictions from the new backpacking equation had a much higher correlation with measured energy expenditures (CCC, 0.93) than the existing LCDA graded walking equation (CCC, 0.44). The median absolute error was considerably lower for the backpacking equation (0.46 ± 0.36 W·kg-1) versus the existing LCDA graded walking equation (1.61 ± 1.32 W·kg-1). CONCLUSIONS: The LCDA metabolic model accurately predicts the metabolic costs of backpacking. Military mission planners, backpackers, and trail walker can rely on improved guidance from the LCDA metabolic model for training, nutritional intake, and heat injury prevention. The views expressed in this abstract are those of the authors and do not reflect the official policy of the Department of Army, Department of Defense, or the U.S. Government.