Predicting how much energy Warfighters use and when they will become exhausted has been completed almost exclusively for males. Differences in physical performance capabilities, body composition, how the body regulates temperature during work, and metabolism may cause different responses in females Warfighters, who are serving in combat roles in greater numbers than before. Sex differences in the energy needs of Warfighter tasks are additional problems that must be addressed. Therefore, the purpose of this study is to determine energy needs during fatiguing Warfighter tasks in a variety of environments.