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Heat Acclimatization


Soldiers need to acclimatize properly prior to conducting PRT in extremely hot environments. Heat acclimatization allows for those specific adaptations that aid in the reduction of physiological stress (heart rate, core temperature, and sweat adaptation). It also improves physical work capability in the heat and builds Soldier confidence. In hot environments Soldiers will safely acclimatize to the heat by conducting PRT sessions during the heat of the day at a lower intensity and volume. For example, PRT can be moved from early morning to late morning or from late morning to mid-afternoon. This allows for acclimatization by gradually progressing to a warmer/hotter environment. Consideration must also be given to wear of the IPFU ensemble (Figure D-2).

Heat acclimatization works on a principle of repeated bouts of heat exposure that are stressful enough to safely elevate core temperature and provoke the sweating mechanism. Limited physical activity accompanied by rest in hot environments will result in only partial acclimatization. Acclimatization requires a minimum daily heat exposure of two hours when combined with endurance and mobility, and strength and mobility training. Research has shown that repeated bouts of shorter duration exercise, like those found in speed running, allow for acclimatization more safely than sustained activity in the heat. Initially, Soldiers will train at a lower intensity and shorter duration, then safely progress, increasing physical exercise intensity, duration, and volume to achieve optimal acclimatization in warm/hot environments. In most cases Soldiers can acclimatize in approximately three weeks. Soldiers will maintain acclimatization for approximately one week with about 75 percent of acclimatization lost within three weeks once the Soldier no longer remains in that environment. Soldiers of low fitness levels or those susceptible to heat injuries may require additional days/weeks to fully acclimatize.

Soldiers must consume sufficient amounts of water to replace water lost due to sweat. Sweating rates greater than one quart per hour are not uncommon. Acclimatization increases sweating rates, which in turn increase water requirements. A risk to acclimatized Soldiers is dehydrating faster than their water intake. Dehydration reduces thermal regulatory advantages achieved through acclimatization and high levels of physical readiness.


Soldiers and PRT leaders must be aware of the signs and symptoms of heat injuries and their severities. They must know how to assess Soldiers who may be at risk and be ready to provide appropriate treatment immediately. If any of the below symptoms of heat cramps, heat exhaustion, or heatstroke are experienced, immediately stop physical activity and seek treatment and/or medical attention.


  • Symptoms: Muscular twitching, cramping, muscular spasms in arms, legs, or abdomen.
  • Treatment: Monitor Soldier in a cool, shaded area, and give water and/or electrolyte sports drink. Call for medical attention if situation worsens.


  • Symptoms: Excessive thirst, fatigue, lack of coordination, increased sweating, cool/wet skin, dizziness, and/or confusion.
  • Treatment: Monitor Soldier in a cool, shaded area, attempt to cool Soldier’s head and body with cold water and give water and/or electrolyte sports drink and await medical attention.


  • Symptoms: No sweating, hot/dry skin, rapid pulse, rapid breathing, seizure, dizziness and/or confusion, loss of consciousness.
  • Treatment: Monitor Soldier in a cool, shaded area, attempt to immediately cool Soldier’s head and body with cold water or ice blanket and give water and/or electrolyte sports drink while awaiting medical attention.


  • Symptoms: Confusion, weakness, nausea, and vomiting.
  • Treatment: Typically misdiagnosed and treated as dehydration. Monitor Soldier and follow treatment for heat exhaustion. If symptoms persist or become more severe with rehydration, replace salt loss and transport immediately to medical facility. DO NOT continue to have Soldier drink more water.
George N.