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: Total Force Fitness
Walk into any fitness center on base or take note of a group of soldiers training, and you’ll probably notice at least a few people in form-fitting synthetic t-shirts. The sports apparel industry has exploded in popularity over the past decade, with numerous manufacturers now competing to develop, market, and sell the newest pieces of clothing (shirts, shorts, underwear, socks), all geared to keep athletes cool while competing or training in hot environments. Is there any science behind these claims? Does tight-fitting clothing made of “high-tech” materials actually help with heat regulation and enhance athletic performance?
You heat up when you exercise, and sweating is the primary method your body uses to stay cool. Sweat evaporating off your skin is the most important method your body has to cool itself during exercise. High-tech materials are supposed to enhance “wicking”—the delivery of sweat away from the skin surface toward the clothing, which allows for evaporation—and limit the absorption of sweat by the clothing itself. Cotton, by contrast, absorbs moisture, so it’s not considered a good choice for exercise.
To date, there’s no evidence that this high-tech clothing improves thermoregulation when worn during exercise in hot environments. Specifically, researchers found no differences in heart rate or body and skin temperatures when subjects performed repeated 20–30 minute bouts of running outfitted in shorts, sneakers, and either a form-fitting compression or traditional cotton t-shirt. Research has also found that wicking sportswear had no effect on cooling when worn under a bulletproof vest or on a cycling sprint when worn under full ice hockey protective equipment. As of now, the best advice for staying cool during exercise in the heat is to wear lightweight clothing, stay properly hydrated, and listen to your body for signs of potential heat illness. For more information on performing in hot environments, please visit the “Heat” section of HPRC’s Environment domain.
Regular physical activity can make you sleep better—but how close to bedtime should you exercise? While the general opinion has been that vigorous exercise within three hours of bedtime might negatively affect your sleep, new research is reexamining this belief. Some preliminary studies have found that exercise before bed (both moderate and vigorous) didn’t negatively impact sleep quality. However, more research is needed to better understand truly how exercise closer to bedtime can impact sleep. Remember—there are many factors that contribute to a good night’s sleep. Just be aware that if you exercise in the evening, it might affect how well you sleep at night. Check out HPRC’s Sleep Optimization section for additional information.
The Food and Drug Administration (FDA) has issued warning letters to 15 companies regarding illegally marketed diabetes products that are in violation of federal law. These products are either dietary supplement products or unapproved prescription drugs with claims that they “prevent and treat diabetes” and “can replace medicine in the treatment of diabetes.”
FDA is warning consumers to stop using these products since they may harmful, and their use may interfere with receiving the necessary medical treatment for diabetes. More information is provided in FDA’s “Illegally Sold Diabetes Treatments,” which includes the news release, warning letters issued, and a consumer update.
Sodium—a component of table salt—is an essential element. It helps your muscles and nerves function correctly and maintains the proper balance of your body’s fluids. However, too much sodium in your diet may increase your risk of high blood pressure, heart attack, stroke, and certain types of cancer.
The average American consumes about 3,400 milligrams (mg) of sodium every day, mostly in the form of salt. But the current Dietary Guidelines for Americans recommends that adults limit their sodium intake to just 2,300 milligrams per day—roughly the amount in one teaspoon of table salt.
The guidelines also recommend that certain “at-risk” groups limit their sodium intake to about 1,500 mg per day: adults over the age of 51, African Americans, and people who have high blood pressure, diabetes, or kidney disease.
Recently, the Institute of Medicine (IOM) looked at the evidence supporting the current recommendations regarding sodium intake. IOM concluded:
- Research supports current recommendations to reduce sodium intake to about 2,300 mg daily.
- More research is needed to support the recommendation that those “at risk” should cut back to 1,500 mg or less a day.
Bottom line? If you’re in an at-risk group, speak to your doctor or registered dietitian about whether you should reduce your salt intake. For just about everyone else: Cut back on the salt.
How? Most of the sodium Americans consume comes from processed foods—tomato sauce, soups, canned foods, bread, and prepared mixes—but it can also come from foods naturally high in sodium—cheese and some types of seafood. Also, many restaurant foods are high in sodium, but sometimes you can request low sodium items. The best way to ensure a low sodium diet is to eat whole foods such as fresh or frozen fruits and vegetables; lean, unprocessed poultry and fish; unsalted nuts; whole grains; and low-fat dairy products such as skim milk or yogurt. For more information, check out this CDC web page.
For additional information and other conclusions from the study, see the news release (which includes a link to the full study) from the National Academies.
The physical demands of military life are challenging, and if you’re not prepared, they can lead to injuries. The injury prevention series we’ll be running over the next several weeks will provide you with information and strategies for preventing some of the most common injuries: those to the knee, ankle, rotator cuff, back, iliotibial band and wrist/hand. Prevention is key: Taking time for the small stuff may have big payoff down the road. Much of what the exercises done for recovery after an injury can actually be done to prevent the injury in the first place. Stay injury-free for optimal performance! Check back soon for the first in this series.
Performing physical activity—whether exercise or mission demands—at moderate (4,000–7,900 ft or 1,200–2,400 m) and high (7,900–13,000 ft or 2,400–4,000 m) altitudes can be challenging. At high altitude, oxygen pressure is lower, which results in less oxygen in the blood and muscle tissues. And as altitude increases, there’s a decrease in air temperature (about 2°F for every 500 ft or 150 m), less moisture (resulting in drier air), and increased solar radiation. Use sunscreen, drink plenty of water, and watch out for the signs of acute mountain sickness: headache, nausea, shortness of breath, and impaired cognition and balance.
To learn more about altitude sickness, read the article “The Invisible Enemy of the Afghanistan Mountains” on the United States Army Research Institute of Environmental Medicine (USARIEM) website. And learn more about performance at altitude in the Altitude section of HPRC's Environment domain.
Have you ever wondered why people who do the same resistance training workouts day after day aren’t getting the results they want? The goal of resistance training is to create an “adaptation response”—that is, to get your body to change in response to the demands. Once your body has adapted to a specific training program, you need to change the demands you place on it. If you don’t, you’ll find yourself eventually reaching a plateau where you don’t make any more gains—or sometimes even lose progress. One way to avoid this common training mistake is to implement “periodization”—the systematic shaking up of your routine (intensity and numbers of sets and reps). This method can optimize your training gains and minimize the risks of overtraining and injury. Implementing these training routines requires a strength training expert, so make sure you seek assistance. For example, the Army has implemented a new program for Master Fitness Trainers. And for more information on strength training, check out the HPRC’s Performance Strategies for Muscular Strength.
If you’re a smoker, you’re probably aware of the products that advertise helping you cut back. One alternative that manufacturers claim is a safe alternative is electronic cigarettes, commonly known as “e-cigarettes.” Their purported safety is largely based on the fact that you’re inhaling tobacco vapor rather than smoke. But are those claims of safety accurate? FDA states that e-cigarettes have not been fully studied, and it is unknown whether they are safe and what their effects are. There is no way for users to know how much nicotine and other harmful chemicals they might be inhaling. According to an article from Quit Tobacco, Make Everyone Proud there are more reasons to think twice
- The long-term impact of using e-cigarettes is still unknown.
- E-cigarettes are not standardized or regulated. Not only are levels of nicotine and other ingredients unknown, but other hazards such as liquid nicotine leaks or battery malfunctions have occurred.
- There also is concern over e-cigarettes appealing to children because many have sweet flavors.
With current and future military operations in mountainous regions, the issue of acute mountain sickness (AMS) is a significant medical concern. AMS can affect anyone, military or civilian, who is unacclimatized and/or ascends too rapidly to high altitudes. Symptoms of AMS can include headache, nausea, fatigue, dizziness, and sleep disturbances. Recently, researchers at USARIEM were able to predict the severity and prevalence of AMS after rapid ascent to various altitudes. What they found was that for every thousand-meter increase in elevation over 2,000 m, a person was over four times more likely to develop AMS. In addition, the severity of sickness doubled, and the odds that the AMS would worsen increased almost five-fold. AMS appeared to peak at 18 to 22 hours of exposure to altitude and then went away after 42 to 48 hours. The severity of sickness is greatest above 4,000 meters and may require evacuation to lower altitude or immediate medical attention. It also appears that men are more likely than women to get AMS and more likely for it to be severe. For both men and women, the more active they were at altitude, the longer it took to recover. These findings support current recommendation to limit activity as much as possible in the first 24 hours at altitude to decrease the risk for AMS.
This information should help military leaders manage and perhaps prevent AMS among troops by knowing the elevation, types of activities, and lengths of stay at altitudes.
In order to reduce the risk for AMS, acclimate to moderate elevations (2,000 – 3,000 m) if/when possible. In addition, stay hydrated and try to limit your physical activity at altitude for the first 24 hours. Read more about the effects of altitude on performance and how to minimize your risk for AMS.
Sugar can be present in foods even when we don’t know it. Some hidden sources of sugar on listed food labels are high-fructose corn syrup, brown rice syrup, brown sugar, honey, maple syrup, glucose, (or dextrose), lactose, sucrose, and the sugar alcohols sorbitol, zylitol, mannitol, and maltitol. Those people watching their sugar intake should read labels carefully to spot hidden sources.