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HPRC Fitness Arena: Physical Fitness

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Supplements alone will not reduce your disease risk

HPRC Fitness Arena:
There's no replacement for a healthy lifestyle–a sound diet and regular physical activity.

Remember, taking dietary supplements alone will not reduce your disease risk. You must engage in complementary behaviors such as healthy eating and regular physical activity. Visit the "Dietary Guidelines for Americans" publication for more information.

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What is heat acclimatization?

HPRC Fitness Arena:

For a more detailed analysis on heat acclimatization, click here.


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.


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Extreme fitness programs

HPRC Fitness Arena:
There’s a trend in the military to move away from the traditional focus on calisthenics and running.

Fitness programs are trending right now, and there's a move away from the traditional focus on calisthenics and running in the military. Our Warfighters are increasingly interested in ensuring that they are optimally prepared to deal with the rigors of being deployed. Most have found that unit physical training programs are not adequate to prepare them for a year of going up and down the mountains of eastern Afghanistan. Therefore, it’s not surprising that many have looked outside the military and are increasingly embracing extreme fitness programs.

Two of the more popular programs are P90X and CrossfitCrossFit. P90X is a commercial, 90-day, home fitness program emphasizing cross-training and varied exercises. The cardiovascular conditioning, strength, and flexibility components are designed to promote overall physical fitness. HPRC has recently posted a review of P90X that looks at the suitability of the program as a readiness tool. CrossFit is similarly a strength and conditioning fitness methodology that combines weightlifting, sprinting, and gymnastics. It has been described as everything from a fitness company to a grassroots health movement to a cult. (crossFit homepage link) Both P90X and CrossFit are designed as intense exercise programs and are not ideally suited to beginners or unfit users.

So what is right for you? This is an important question, but difficult to answer because of the lack of research associated with popular intense fitness programs. Both of the programs referenced above have shown good results with a large number of practitioners. There has, however, been a history of muscle damage (rhabdomyolysis) associated with each program. This is a dangerous condition where muscle fiber breaks down and is released into the blood stream, poisoning the kidneys.

To determine what the right fitness program is for you, it’s important to consult the experts in your organization. Talk to your supervisor first and ensure that you are matching your fitness program to your functional job requirements. Each of the Services are moving toward functional fitness programs and leaders are increasingly shifting away from a focus on the “daily dozen.” What you are looking for in an exercise program might be available in your unit or on your base. You should also consult your local health provider. They will be able to help you establish your baseline fitness level and determine how aggressive you can be initiating a new and more intense fitness program. They can also help you establish a program to ramp up from this baseline that puts you on a path to continually improve your fitness level without getting injured.

Because of the necessity for better information on the risks and benefits associated with extreme fitness programs, HPRC will host a conference prior to the end of the fiscal year 10 (FY10) that will include some of the leading experts on the subject from across the country as well as representatives from each of the Services. The conference will be held at the Uniformed Services University of the Health Sciences. If you are interested in getting information on the conference please send us a note at the “contact us” button on the HPRC homepage. The intent of the conference is to ultimately establish the right framework to push the fitness envelope and to dramatically reduce the risk of injury.

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After heatstroke, when is it safe to exercise?

HPRC Fitness Arena:
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.

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.

See the full text of this article.

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The barefoot running question

The book Born to Run by Christopher McDougall has been a primary catalyst for the rapid expansion of the population of “barefoot runners” over the past year.

The book Born to Run by Christopher McDougall has been a primary catalyst for the rapid expansion of the population of “barefoot runners” over the past year.  Most barefoot running advocates are in reality minimalist runners – they wear as little on their feet as possible.  In most cases they wear just enough to provide a little cushion on concrete or other hard surfaces or to provide a thin layer of protection from glass or other sharp objects. Minimalist footwear is referred to as “barefoot technology,” which, at some level, seems to be an oxymoron.  The cynical side of me says the term was coined by those expecting to make money off a new trend.

It is important to first note that there is no evidence-based information to support either side of the debate on the efficacy of being either shod or unshod.  The most interesting research pointing toward the possible advantages of the minimalist approach is outlined by a Harvard professor and his colleagues in a January 2010 edition of the journal “Nature.” A counter to the assertion that barefoot running is beneficial can be found on a website titled “Barefoot Running is Bad.” The pro barefoot running community points to initial research that indicates there is more force absorbed by the body by a runner wearing shoes than by barefoot runners.  The greatest difference is that barefoot runners have a forefoot strike, while runners wearing modern running shoes tend to have a heel strike. The opposition community points to anecdotal information that there has been a rapid rise in the incidence of stress fractures in the feet of barefoot or minimalist runners.

For me, the jury is still out.  I find the concept that we should allow our feet to function as designed intriguing. My advice to those in the military interested in transitioning to a barefoot regimen is to first consult their local provider for advice. In addition, anyone starting a barefoot running program should increase the barefoot component of their normal workout routine gradually. A good rule of thumb is to increase the barefoot part of the program by no more than 10 percent each week.  Barefoot adherents should also listen to their bodies and stop any activity that leads to joint or soft tissue pain.

My closing concern: warriors, regardless of where they are assigned, will spend a considerable amount of time in some sort of boot technology while training or deployed.  As the sports medicine community debates the value of being barefoot in contrast to lacing up the latest Nike technology, we need to determine if there is any advantage for warriors adopting a partial or full barefoot workout program.  This research should include an assessment of the positive or negative effects of frequently transitioning between minimalist footwear and boots.  As more warriors get the minimalist footwear bug, it is important that we provide them the best evidence-based information that supports or argues against the practice.

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Diet: Major piece of soldier's health, fitness puzzle

HPRC Fitness Arena:
As Army Chief of Staff Gen. George W. Casey Jr. stresses the Comprehensive Soldier Fitness Program, the U.S. Army Sergeants Major Academy finds itself at the tip of the spear in offering health and fitness insight to its enlisted members.

By G. A. Volb | Army News Service

May 24, 2010

As Army Chief of Staff Gen. George W. Casey Jr. stresses the Comprehensive Soldier Fitness Program, the U.S. Army Sergeants Major Academy finds itself at the tip of the spear in offering health and fitness insight to its enlisted members.

Senior Army leadership not only wants a broadly-skilled NCO treading the battlefields of tomorrow, but one that is both physically and spiritually fit. The former is a product of fitness regimens designed to enhance Soldier's ability to withstand the stresses and challenges of today's real - world operations tempo – and diet, not surprisingly, is a major piece to the puzzle.

Dietician Mrs. Jennifer Eiland, left, discusses possible changes Master Sgt. Anthony Jones may want to consider regarding his diet to help better his overall fitness. Jones, a Philadelphia, Pa., native lost nine pounds in just over a month following his initial meetings with Eiland. "I just used a few common sense diet and lifestyle changes that Jennifer suggested," the 44-year-old Jones said. (Photo Credit: G.A. Volb)"The food choices you make and when you eat have a direct impact on your energy level, ability to concentrate, overall feeling of well-being and gut function," said Jennifer Eiland, a dietician and part of the Army Physical Fitness Research Institute's staff at their USASMA annex. "It also affects your ability to complete an exercise session."

Casey, it should be noted, is so big on Soldier fitness that he's made the CSF Program, established in 2009, a priority as the Army tries to focus on the five dimensions of strength: Physical, Emotional, Social, Spiritual and Family.

The general's intent is to increase the strength, resilience and enhance performance of all Soldiers, family members, and Department of the Army civilians. None of it is possible if the old quip, "You are what you eat" makes sense and everyone is shoveling junk food down their necks.

"Diet is extremely important to realizing health and fitness goals," said the 25-year dietitian from Roy, Utah. "It influences almost three-quarters of the results of our health assessments. It can also influence a person's aerobic capacity; heavier participants typically have lower V02 or lung efficiency as a result. Mood and alertness are also affected by diet."

She stressed that eating a diet full of sugar, salt and fat lowers one's energy level and ability to concentrate, which in turn, can negatively affect school work and a Soldier's performance.

"It affects chronic disease risk on a number of levels as well," she offered. "Obesity increases the odds of contracting cancer, diabetes, heart disease and high blood pressure. Excessive sodium intake can increase blood pressure in over two-thirds of the population and risk of stroke and heart attacks according to the latest from the American Heart Association and Centers for Disease Control."

In a recent letter to the troops, Sgt. Maj. of the Army Kenneth Preston emphasized the need for Soldiers to work on all five areas stressed by the CSF Program; most of which can be affected by diet.

"We want CSF activities to become a part of our daily lives, just as we do physical training every day to build and strengthen the physical dimensions of CSF," said Preston in his letter. "We want the members of our team to do more than just cope with adversity; we want them to grow from their life experiences."

"Reflecting on the past eight years of war and our deployment experience in Afghanistan and Iraq, we can now begin to understand the individual health and resilience problems associated with our deployment tempo," he said.

An unhealthy Soldier is less effective," said Eiland. "A sergeant major's overall health, including how he or she eats, influences their ability as leaders ... and the influence they have on the health choices of their young Soldiers."

Eiland pointed out that a prominent group of retired military leaders want junk food taken out of America's schools because the obesity epidemic, especially in young people, is limiting the number of people who can be recruited into the military, making obesity a national security issue.

On a positive note, she added that many Soldiers have a sincere interest in improving their eating habits.

"A good majority tend to eat more meat and fewer fruits and vegetables than is considered optimal for good health," said Eiland. "Including more whole grains and less processed foods is also an area I frequently discuss with Soldiers. Sugary beverages seem to be a favorite as is eating fast food and microwave meals given their busy schedules. However, if dietary changes are presented in a practical and doable way to them, most will make changes."

The major challenges, according to the dietitian, are getting organized and planning ahead.

"Enlisting uncooperative family members, finding time to cook their own meals and changing an old mindset are also challenges," she said.

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