Terrain Factors for Predicting Walking and Load Carriage Energy Costs: Review and Refinement

Abstract

The ability to predict the energy cost of load carriage is important to various disciplines and applications including anthropology, exercise physiology, humanitarian aid, and dismounted military operations.  Energy consumption in turn determines the physiological status of individuals and populations and their ability to function via internal heat production, hydration, fatigue, and caloric intake.  Various parameters of the physical environment, including topographic relief and surface conditions impact those energy costs. To be comprehensive, predictive load carriage cost models must incorporate body mass, load, positive and negative grades, and adjustments for surface conditions.  Models developed at the U.S. Army Research Institute of Environmental Medicine (USARIEM) in the 1970s incorporated an adjustment for surface conditions, i.e. a terrain factor.  However, the terrain factors were derived empirically from data for a relatively limited set of surface conditions or classes.  Aside from efforts to apply the classification of terrain factors to a broader set of conditions, little work has been done on to improve terrain factors since the 1970s.  This paper reviews the effect of terrain properties on locomotion, the development of terrain factors, and provides scientific improvements based on the parallel studies of vehicular trafficability at the U.S. Army Cold Regions Research Engineering Laboratory (CRREL).