The Impact of Load and Grade on Energy Expenditure During Load Carriage, Part II: Field Study

Abstract

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...

Altitude Acclimatization Alleviates the Hypoxia-Induced Suppression of Exogenous Glucose Oxidation During Steady-State Aerobic Exercise

“…Exercise sessions included low to moderate intensity treadmill walking, running, and outdoor hiking, all supervised and documented by research personnel to ensure safety and compliance with the exercise prescription. The amount of physical activity necessary to elicit the desired daily EIEE during altitude acclimatization was individually prescribed, and determined using the Pandolf Equation for level and uphill walking ( Pandolf et al, 1977 ), adjusted as necessary for downhill walking ( Santee et al, 2003 ). Changes in body mass and composition during HA acclimatization phase are presented and discussed in detail separately ( Berryman et al, 2018 ).…”

Modeling the Metabolic Costs of Heavy Military Backpacking

“…The LCDA predicts physiological responses of warfighters during dismounted operations using biomedical models developed at the US Army Research Institute of Environmental Medicine (USARIEM) (1,2). Notably, USARIEM developed equations in the 1970s and 1990s that predict the metabolic costs of foot marches with military loads over complex terrain (3)(4)(5). However, these earlier equations underestimate the metabolic costs of heavy military load carriage (6)(7)(8)(9), particularly at slower walking speeds (2), steep downhill grades (10), and while carrying contemporary military equipment (7).…”

Improved heat coefficients for joint-space metabolic energy expenditure model during level, uphill, and downhill walking

“…In addition to calculating the RMSE for the current model, seven other MEE models are included for comparison. These included two muscle-based models [ 13 , 14 ], three empirical predictive equations [ 7 – 10 ], and two joint-based models [ 17 , 18 ]. The two muscle-based models are chosen because they are readily available within the OpenSim software which means that they are easily accessible to users.…”

“…Empirical predictive equation formulations are typically simplistic, where whole body metabolic energy consumption is estimated by using few input variables. Some depend only on grade [ 6 ], while others are a function of a combination of speed, grade, load carriage, body mass, terrain coefficients, and oxygen consumption [ 7 – 10 ]. These models can be very accurate when applied and they are easy to use, but they are limited to the specific task that they are validated for like walking or running and cannot always account for tasks beyond that scope.…”