Filed under: Environment
Even wonder why HPRC refers to the sections of its website as “domains”? They came from an initiative within the Department of Defense that’s outlined in a special issue of Military Medicine titled “Total Force Fitness for the 20th Century: A New Paradigm.” Experts identified eight “domains” of fitness that contribute to the optimal, overall fitness and preparedness of U.S. military forces. With some reorganization (and one exception – medical), these domains are represented on HPRC’s website—Physical Fitness, Environment, Nutrition, Dietary Supplements (originally part of nutrition), Mind Tactics (psychological, behavioral, and spiritual fitness), and Family and Relationships (family and social fitness)—along with a section on Total Force Fitness that addresses how these domains come together to create Human Performance Optimization (HPO) for our military service members.
If you exercise in the cold, consider these tips from the American Council of Exercise (ACE; Exercising in the Cold) to stay safe. Check how cold it is before you go out, and do not exercise if the conditions are too extreme. Be sure to dress warmly (keep your head, hands, and feet warm) and dress in layers that can trap insulating dry air near your skin. In addition, avoid blowing air into your gloves and mittens because it will add moisture, which will cause your hands to be colder. For more detailed information, you can read the original American College of Sports Medicine position stand: prevention of cold injuries during exercise.
Warfighters are deployed to all kinds of environments, including hot and dry conditions where sun exposure is a concern. Choosing a "broad-spectrum" product that protects against sunburn, skin cancer, and premature skin aging is important, but product labeling can be confusing. Now, however, the Food and Drug Administration (FDA) is taking steps to regulate the labeling of sunscreen products in order to help consumers choose a product that will protect them from sun damage to the skin.
The new measures include a regulation, effective one year from now, that requires sunscreens to undergo a standard test if they want to be labeled as a “broad spectrum” product. Those that pass the test will be allowed to use “broad spectrum” on their packaging, which indicates a product that provides protection against both ultraviolet B radiation (UVB) and ultraviolet A radiation (UVA). UVB rays are primarily responsible for sunburn, but both UVA and UVB rays are harmful and can cause sunburn, skin cancer, and premature skin aging.
Other provisions in the FDA regulation include:
- A warning about the risk of skin cancer and early skin aging on the labels of sunscreen products that are not broad spectrum.
- The amount of time the consumer can expect protection from a product with water resistance claims must be stated on the front label. The FDA, based on standard testing, will allow either a 40-minute or 80-minute timeframe on labels.
- Products will no longer be allowed make a claim of “waterproof” or “sweatproof” or use the term “sunblock,” nor can they make the claim of immediate or instant protection or protection for more than two hours without reapplication.
Additional measures regarding the labeling of sunscreen products have been proposed. To learn more, view the FDA’s full article.
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.
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.
Heat-related injuries are a significant threat to the health and operational effectiveness of military members and their units. The human body’s response to heat stress is quite resilient if given several weeks for adaptation to occur. This process, called acclimatization, involves internal adjustments, in response to the outside environment, which improve heat tolerance. This adaptation can be fully achieved after 10 to 14 days of exposure to heat, but two-thirds, or even 75 percent, of the adaptation takes place within five days.
Myths and/or Claims
1) It is commonly believed that warfighters who are physically fit do not need to be heat acclimatized.
2) It is also assumed that older individuals are less heat tolerant than their younger counterparts.
3) Women are thought to need longer acclimatization time, since they are more vulnerable to heat illness.
1) Though fit warfighters acclimatize faster than less fit warfighters, a physically active person cannot be fully acclimatized without exposure to environmental heat stress.
2) Age has no effect on acclimatization. Research that controlled for body size and composition, aerobic fitness, hydration, degree of acclimatization, and chronological age showed little or no age-related decrements in one’s ability to manage or acclimate to extreme temperatures.
3) Nor does gender appear to be a factor: women were thought to need longer acclimatization, since they are more vulnerable to heat illness. However, women and men show equivalent thermoregulation during exercise when levels of fitness and acclimatization were controlled.
4) Heat-related injuries such as exertional heat illness remain a major cause of illness and occasional fatalities within the Armed Forces. However, as mentioned earlier, the human body’s can be resilient to heat stress if given several weeks to adapt.
Heat acclimatization adaptations may vanish after only a few weeks of inactivity (i.e., 18-28 days). The first adaptations to degrade are those that develop first: heart rate and other cardiovascular variables.
Summary for Military Translation
Studies have shown that acclimated soldiers suffer no detrimental effects of exertional heat stress, despite almost the same degree of heat strain. The Technical Bulletin-Medical 507 provides an evidence-based preventive program to protect military personnel from heat stress and associated adverse health effects. The recommended heat acclimatization strategies are to mimic the deployment climate, ensure adequate heat stress (i.e. by invoking sweating, having 4 to 14 days of heat exposure, and maintaining the daily duration of at least 100 minutes). It is also suggested that heat acclimatization start at least one month before deployment; and upon arrival, acclimatization should start slowly and build up by increasing heat and training volume as tolerance permits.
A.Nunneley, S. (2009). Prevention of Heat Illness Medical Aspects of Harsh Environments, Volume 1: U.S. Army Medical Department's headquarters
Armstrong, L. E. (Ed.) (1998) Encyclopedia of Sports Medicine and Science.
DOD. (2010). Update: Hear Injuries, Active Component, U.S.Armed Forces, 2009. Medical Survillance Monthly Report, Vol.17.
Lugo-Amador, N. M., Rothenhaus, T., & Moyer, P. (2004). Heat-related illness. Emerg Med Clin North Am, 22(2), 315-327, viii. doi: 10.1016/j.emc.2004.01.004S0733862704000057 [pii]
McArdle, W., Katch, F., & Katch, V. (2007). Exercise physiology. Energy, Nutrition & Human Performance (Sixth ed.): Lippincott Williams & Wilkins.
Radakovic, S. S., Maric, J., Surbatovic, M., Radjen, S., Stefanova, E., Stankovic, N., et al. (2007). Effects of acclimation on cognitive performance in soldiers during exertional heat stress. Mil Med, 172(2), 133-136.
USACHPPM. (2003). Heat stress control and heat casualty management.