Welcome to the HPRC Blog. We've got lots of information here, from quick tips to in-depth posts about detailed human performance optimization topics.
HPRC Fitness Arena: Environment
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.
With the hot sun of summer, make sure your skin is protected when exercising outdoors. This isn't just a cosmetic issue, but a health issue, as well. Apply enough sunblock of the correct type for the exercise you're performing outdoors. Visit Environment, Health, and Safety Online for general sun safety tips.
Swimming is a great way to stay cool this summer and get a great workout. Try variations with strokes and swimming equipment like kickboards and fins. For more swimming tips to improve your fitness, visit Medicinenet.com.
When performing physical activities in the heat, avoid drinking liquids that contain alcohol or large amounts of sugar since these actually cause you to lose more body fluid. Also avoid very cold drinks, because they may cause stomach cramps.
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.
From the June 15, 2010 edition of the New York Times.
Heatstroke is a potentially deadly consequence of exercising. "This is a very controversial area, even more so than concussions," said Dr. Francis G. O'Connor, president of the American Medical Society of Sports Medicine. He moderated a debate on the topic at a recent meeting of the American College of Sports Medicine.
Researchers at USARIEM conduct research on military performance in high altitude environments and published their findings in Altitude Acclimatization and Illness Management Guidelines this year.
Their recommendations? Staying hydrated, healthy eating and refraining from smoking helps Warfighters to perform in high altitude environments. Click here for more information and recommendations for performing optimally in high altitudes.