It is considered cold if the air temperature is below 15° F and the wind speed is greater than 25 m.p.h, or the water temperature is below 64oF. Cold environments increase energy metabolism and urination.
Soldiers can progressively lose weight when conducting field exercises in the cold for two to three weeks. Because this weight loss can cause fatigue and performance decrements, energy intake must increase to meet the increased energy demands. Energy requirements can increase 25 to 50% in the cold. To meet the increased energy and fluid needs, follow the guidelines on page 73. Also,
vitamin and mineral needs may increase, so eat all ration components to meet these needs.
Ascent to altitude can cause a variety of physiologic disturbances due to the drops in temperature and humidity, and the lack of oxygen. Some major concerns are weight loss, disturbances in digestion, nutrient and fluid needs, and Acute Mountain Sickness (AMS). Adequate nutrition can play a crucial role in maintaining health and performance at altitude.
Energy requirements are 15-50% greater at altitude than at sea level. Virtually everyone who goes to higher altitudes experiences weight loss and loss of muscle mass. At altitudes below 5,000 m weight loss can be prevented by increasing your kcal intakes. Weight loss is inevitable above 5,000 m. To meet the increased energy and fluid needs at altitude follow the guidelines on page 73.
Vitamin and mineral needs are likely to increase at altitude. In particular, the increased metabolic rate and the lack of oxygen can increase the production of harmful free radicals. Preliminary research indicates that taking 400 IU per day of vitamin E, an antioxidant, at high altitude reduces free radical production.
As noted throughout this chapter, meeting energy and fluid requirements are vital to maintain physical performance in adverse environmental conditions. Being physically fit and eating a healthy diet prior to deployment will greatly improve your adaptation to the new environment.
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