IntroductionThis study is a continuation of our research (Santee et al., 2001) to quantify the metabolic cost of load carriage by expanding the database to include load carriage under field conditions. The primary purpose of the study was to obtain data under field conditions and use it to validate predictive algorithms developed from our previous laboratory study. At present, predictive thermoregulatory models and simulations, including SCENARIO (Kraning and Gonzalez, 1997), the Integrated Unit Soldier Simulation (Ramirez and Hoffman, 1994) and the Close Action ENvironment CAEN (Demczuk, 1998) simulation are limited in their ability to accurately predict energy expenditure for locomotion over negatively sloped terrain. Our algorithms provide those additional energy cost estimates.The following introductory comments are intended to illustrate the complexity of load carriage, especially under field conditions. As these factors simultaneously impact the energy requirements for load carriage, the data presented in this study cannot wholly discriminate between these factors. Thus while we can speculate on the impact of different factors, the study is focused on the relative fit of the algorithm predictions to the observed data.The problems with downhill movement, including load carriage, are well known. Earlier investigators (Pimental and Pandolf, 1979; Magaria, 1968;Minetti et al., 1998, Wanta et al., 1993 had observed that the minimum energy requirement for walking occurred on negative slopes. The principal problem is that multiple forces are acting upon the same muscles. A simple explanation is that 2 factors are involvedgravity or negative work involving vertical displacement, and metabolic costs including maintenance or baseline metabolism, the muscular work to move or accelerate the body forward, and energy expanded to maintain stability. Stability is generally thought of as braking to maintain control at increasing downward speeds, but there may be some cost associated with controlling lateral deflection.In terms of biomechanics, the problem involves eccentric work in which opposing forces act simultaneously on the same muscles. Due to the relative complexity of the multiple factors, relatively few models have been proposed. Minetti et al. (2002) published models for up-and downhill walking and running, but their emphasis is on competitive events without significant loads. Laursen et al. (2000) tested a biomechanical model for up and downhill walking with and without hand-held loads on a treadmill. DemczukJournal of the Human-Environmental System Vol. 6; No. 2: 69-76, 2003 Application of Energy Cost Algorithms for Load Carriage to Field Data AbstractThis study measured the energy requirements for load carriage on uphill, level and downhill grades. These field data were used to test our algorithms for estimating the energy cost of load carriage. Volunteers carried pack loads of 0 kg, 13.6 kg or 27.2 kg as they walked on level and downhill grades of 0%, 4%, 8.6% and 12% at 1.34 m · s ؊1 . Subjects attempt...

Public reportinq burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, □atherinq and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway Suite 1204 Arlington, VA 22202-4302, and to the Office of Management and Budget, Paperwork Reduction Project (0704-0188), Washington, DC 20503. AGENCY USE ONLY (Leave blank). REPORT DATE The metabolic costs of load carriage were measured for 8 volunteers on uphill, level and downhill grades at Yakima Training Center (YTC). Volunteers carried loads of 0, 13.6 or 27.2 kg as they walked on grades of 0% (level), ±4%, ±8.6% and -12% at 3 mph. Mean values for oxygen consumption (V02) during load carriage indicate costs increased with increasing load and uphill grade, and decreased with negative grades. A mathematical model, using a terrain factor of 1.1 for sites with gravel, was used to calculate load carriage costs. Those values were compared to field data. Results for the negative data showed no significant difference between the model and downhill measurements. For the +8.6% grade there was a significant difference between the measured and model calculated values, which underestimated the measured costs. Results obtained under field conditions were also compared to results obtained under laboratory conditions on treadmill grades of 0%, ±4%, ±8% and -12%. When the field data were compared to laboratory values, the field data were also higher than the laboratory data. It is possible that the difference between observed and model calculated values reflects a difference between laboratory and field conditions. BACKGROUNDThe development of predictive models is an assigned mission of USARIEM under ST03U. This study was in response to a specific need for input into models being developed by USARIEM and for cooperative projects with other organizations such as the IUSS being developed by the U.S. Army Soldier Biological and Chemical Command (SBCCOM). The data collected during Phase II was used to evaluate a model developed from data collected during Phase I and will be used to validate other models under development. The telemetry temperature pill and activity monitor are prototype components of the Warfighter Physiological Status Monitor (WPSM). This study also presented an opportunity to expand the performance database for these sensors during controlled field use. VI ACKNOWLEDGMENTS EXECUTIVE SUMMARYThis study is an expansion of a previous laboratory study that measured the metabolic energy requirements of load carriage over positive (uphill), level and negative (downhill) grades. By expanding the limited data for load carriage over sloped terrain to include field tests, th...