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HPRC Fitness Arena: Environment
Heat-related injuries are a threat to Warfighters, even those in top physical condition, deployed to extreme environments. Heat acclimatization is necessary to ensure that the health and performance of Warfighters is not compromised to a dangerous degree when exposed to heat stress.
Take it slow. For unacclimatized Warfighters, physical exertion should be limited in intensity and time. Allow 9-14 days of progressive heat exposure and exertion—more for less-fit Warfighters, less for more-fit Warfighters.
Don’t overdo it; don’t underdo it! Heat acclimatization requires exposure at least two hours per day (can be two one-hour segments) while engaged in a cardiovascular exercise (which should increase in intensity each day of the acclimatization period).
It’s all relative. The level of heat acclimatization achieved is relative to the exertion normally expended by the Warfighter. If light exertion is the norm, the level of heat acclimatization after two weeks will match that. If more strenuous exertion is called for, additional acclimatization and possibly improved fitness is required.
Work smart. If Warfighters must perform physical work during the acclimatization period, take advantage of the cooler hours during the morning, evening, and night.
Stay hydrated. Adequate water is essential. Heat acclimatization increases sweating and, therefore, water requirements. Dehydration rapidly degrades safety and performance, even for those who are already heat acclimatized or in top physical condition.
For a more detailed look at heat stress and acclimatization, read HPRC’s reports on managing heat exposure.
Research at USARIEM (U.S. Army Research Institute of Environmental Medicine) was featured in a article by writer Christopher Solomon titled "G.I. Joe and the House of Pain" in a special issue of Outside Magazine about human performance. The author spent time in the research lab's heat chamber, altitude chamber, and cold-water pool—conditions that simulate the extreme environmental conditions found in theater. He interviewed research physiologists there about USARIEM's work over the past 50 years as well as its current studies, all of which address the crucial issues of Warfighter health and performance in extreme environments.
Men and women in the military who operate in and around open water need protection against drowning and immersion syndrome. Quick response to cold-water immersion is important because of its immediate impact on the body. Immersion syndrome could cause cessation of breathing and/or cardiac arrest in certain people. Cold water causes a loss of heat much faster than cold air does and can quickly cause performance impairments such as not being able to fasten a life jacket or other safety equipment. Making an effort to tread water or swim only increases the body’s heat loss and hastens the onset of hypothermia.
A person alone can extend survival time by using body posture that covers areas especially vulnerable to heat loss. Those in the water should avoid movement and use the “heat-escape lessening posture” (H.E.L.P.). This posture minimizes the exposure to cold water of the individual’s groin and chest because the arms are folded across the chest and pressed to the sides and the knees are drawn up with the legs crossed at the ankles, creating a fetus-like position (see figure 13-6 in the article linked above for an illustration). Note that this technique does require the use of a personal floatation device that allows the knees to be drawn up.
If more than one person is involved, the “huddle position” should be used to reduce heat loss. In this position, individuals should press together their chests, abdomens, and groins. In addition to conserving each individual’s body heat, the huddle position helps prevent the swimmers from becoming separated before they are rescued, provides a larger rescue discovery target, improves morale, reduces shock and panic, and may reestablish a chain of command.
These survival techniques require practice and the use of personal flotation devices. Treading water in the H.E.L.P. position in heavy seas is a major challenge, and the huddle position requires that all participants be able to tread water, so being fit and prepared is essential.
The amount of the time spent sleeping is decreasing: the average amount of sleep reported for middle-aged people in the late 1050s—around eight to nine hours—has decreased in recent times to about seven or eight hours. And the number of individuals who sleep less than six hours each night has significantly increased. These changes in sleep patterns may be indicative of sleep deprivation in society at large. This is not surprising, as the modern society seems to offer twice as much work (on the job, at home, etc.) and half as much time to complete it. Consequently, we are awake for extended periods of time, thus reducing the amount of time we spend sleeping.
However, we all know that sleep is essential! Sleep is vital to restore and renew many body systems; and sleep deprivation may result in poor performance, increased sleepiness, reduced alertness, delayed response time, difficulty maintaining attention, decreased positive mood, and increased long-term health risks. Some research studies have even shown that sleep deprivation is associated with increased risk of death.
So adequate sleep is vital for everyone to optimally perform the activities of daily living. But you may wonder, “How can I determine how much sleep I need to function at my best?” Dr. Michael Bonnet, director of the Sleep Laboratory at the Dayton. Ohio, Department of Veterans Affairs Medical Center provides a very simple but practical test you can use to determine how much sleep you need. According to him, if you need an alarm clock to wake up, try going to bed a little earlier the following night (e.g., 15 minutes earlier). If you still need an alarm clock to wake up the next morning, push your bedtime a little earlier again (i.e., another 15 minutes). Continue doing this until you no longer need an alarm to wake up.
I actually tried this test and found out I was not the “night owl” I thought I was. It looks like I function at my best if I retire for the night a couple of hours earlier than I used to. Sleep is important! It significantly affects your performance, health, and quality of life. And it is especially important to Warfighters, who can rarely get enough when deployed. So in addition to a healthy diet and regular exercise, try to get enough sleep each night whenever your situation makes it possible.
Source: National Sleep Foundation
Science Daily reports on a new study published in the Journal of Applied Physiology which indicates that training in warm weather not only improves heat acclimation and performance in the heat, but also improves performance in cool conditions. Click here for more details about the study.
Scuba diving is a risky sport. Divers should have a positive attitude, good level of physical fitness, and avoid exhibiting unsafe behaviors to minimize the risk of having a diving accident. Read more about safe diving practices avoid adverse events during a dive.
Runnersworld.com has an article that cites a new study from the Journal of Applied Physiology which reports that 10 days of extreme heat acclimation can improve performance by six to eight percent.
Click on link below to access article.
Keeping physically fit is an important part of a military career. Aboard the USS Kearsarge Marines and sailors merge creativity and enthusiasm to push their physical fitness to even higher peaks. The October 05, 2010 edition of Military Health System News has an article on how Marines and sailors aboard the USS Kearsarge find ways to supplement their physical training while at sea.
If you sweat a lot during exercise, be sure to drink lots of fluids – but do not exceed 1.5 L/hour. Sip frequently rather than gulp; drinking small amounts of fluids at a time are more effective than drinking large amounts occasionally. Also, start drinking before you become thirsty. Click here for more information.
Whether you are working out or relaxing, the summer sun can damage your skin. The American Academy of Dermotology recommends that you use a sunscreen of SPF 15 or higher, apply 15 to 30 minutes before going outdoors, and reapply every two hours. Make sure to cover all of your skin and use even if it’s cloudy outside.