Summer is here, bringing months of fun and sun. Although the warmer weather is a welcome change after winter and spring, the threat of heat comes with it. We can feel the effects of higher temperatures anywhere, from normal operations at home base to worldwide contingency operations. Counteracting heat-induced effects is essential for a military unit to sustain operations-especially flying. There is no doubt hydration is one of the keys to success in combating this danger, but what's the best way to accomplish it? In the past, the answer was easy: drink water. However, this has changed because now we have scientifically engineered sports drinks. So, the question must be asked: 'What works best for hydration, water or a sports drink?'
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Pilots regularly encounter heat and the effects of dehydration it causes on their bodies. The dangers of dehydration are caused by its insidious and relatively quick onset. The effects are very subtle because we are exposed to them often without realizing it, and they can occur in as little as 50 minutes of outdoor activity in a hot climate. (1) The common physiological symptoms of dehydration are thirst, fatigue, irritability and impaired mental focus. These symptoms may seem mundane because some individuals experience them every day, and the extent of impairment varies from person to person.
So, how does this directly apply to flying operations? Consider what a pilot goes through between briefing and takeoff for a mid-day sortie in July. For this general example, a step time of one hour is used. At step time, the pilot shows at the squadron ops desk dressed to fly with all his gear. The pilot then steps to the flightline after receiving the step brief from the squadron Top-3. Ten minutes after step time, the pilot arrives to the assigned aircraft's parking spot. These ten minutes can occur mainly in an air-conditioned environment and may not impact the flyer physiologically. Arriving at the aircraft, the pilot reviews the forms and performs a walk-around for 10 to 15 minutes. Upon entering the (warm) cockpit, the pilot spends 15 minutes running ground ops then taxis 15 to 20 minutes before takeoff. The cockpit will not cool to an environmentally neutral temperature until just before takeoff. An environmentally neutral temperature causes limited dehydration in a static individual through sweating (usually 65-75 degrees Fahrenheit). Taking this example into consideration, a pilot about to launch for a sortie has been exposed to a hot environment (greater than 90 degrees Fahrenheit) for close to 40 minutes. This means noticeably degraded mental and physical performance caused by dehydration could occur within the first 30 minutes of flight. Dehydration will likely occur sooner because this example assumes the pilot to have optimal hydration at step. This doesn't take into account the morning coffee (or several), and caffeinated beverages throughout the day.
Dehydration is defined in terms of percent loss in body weight of sweat (greater than three percent). Slight dehydration, one to two percent loss in body weight, is enough to cause a negative impact on human performance. The effects of dehydration are difficult to detect, and the normal human thirst mechanism is too inefficient--the focus must switch to the cause of dehydration. Since we define dehydration in terms of percent of body weight loss due to sweat, the amount of perspiration serves as a useful indicator of how quickly we are dehydrating.
To apply this, use the example of the pilot above. During level-off, the pilot notices a higher than normal sweat rate. Let's assume he is a moderate sweater-one liter per hour. In order to return to an optimal hydration or at least his hydration level before stepping, the pilot would have to drink one liter of fluid. The best fluid replacement technique requires consumption in evenly-spaced intervals. Therefore, the pilot would drink eight ounces of fluid every 15 minutes to achieve the desired effect. Unfortunately, for most pilots, taking a drink break every 15 minutes is not always possible. However, rehydration is still achievable if the pilot uses the resources made available in life support. By using two green flasks, the pilot would have approximately 24 ounces of fluid (1 liter) for rehydration. With one flask in each G-suit pocket, the pilot could drink one on departure and the other after completing range work. This replaces the fluid lost in the hour of sweating before getting airborne, but it does not take into account the sweat lost during the sortie, which would require more fluids. It also raises another issue, not all sorties are limited to one hour, and cockpits only have so much room to accommodate flasks and water bottles.
Hydration with water will combat dehydration. The water intake must equal the fluid lost sweating during any activity. Unfortunately, water does have a few drawbacks. First, water is an excellent thirst quencher despite being tasteless. At first look, this appears to be good, but if drinking only a small amount of water makes an individual stop hydration, that person will have to rely on willpower alone to continue drinking. This creates a problem if an individual needs to drink large amounts of water. Second, water does not replenish electrolytes, which directly relate to muscle fatigue. According to Chris Carmichael, Lance Armstrong's training coach, this is not a problem for short duration physical activity (i.e., a one hour sortie). (2) However, this does become a factor in longer duration sorties, say a pit-and-go day. In order to stay hydrated for a multi-sortie day, the pilot now has a cockpit full of water bottles with little space to store all of them (not to mention the piddle packs this might cause). There must be a better solution.
The best solution for combating dehydration relies upon the use of sports drinks. Scientifically engineered sports drinks are designed to improve physical performance by encouraging fluid intake and promoting rapid rehydration. (2) Sports drinks have a balance of taste, electrolytes and nutrients that enable an individual to rebound faster and better from the effects of dehydration than by just using plain water. Sports drinks encourage fluid intake by being slightly sweetened with the presence of sodium. (1) This combination is designed to taste best to a hot, sweaty and thirsty individual. The electrolytes and nutrients in the sports drinks help reduce and prevent fatigue. In addition, sports drinks can achieve hydration status with less than 100 percent of fluid replacement. According to Carmichael in his book, Food for Fitness, performance will not improve any more by consuming more than 80 percent of fluids lost, as long as 50 to 60 percent of replacement fluids are sports drinks. He also states this is only true for sports drinks that include electrolytes and carbohydrates. This means that instead of carrying two 12-ounce flasks, one 20-ounce bottle would suffice in the above example. The ability to use less than a one-to-one ratio of fluid lost allows pilots to stay hydrated longer on less fluid quantity, and helps with limited cockpit space.
Dehydration is common for pilots and directly impacts the ability to perform operations, especially under stressful situations. We've depended on water for years, but improved products are available. Other hydration options may prove more valuable. A hydration plan including sports drinks creates an effective way to keep pilots performing at their best.
References:
(1) Murray, Bob, PhD, FACSM. Preventing Dehydration: Sports Drinks or Water. Gatorade Sports Science Institute. HYPERLINK 'http://www.gssiweb.com' http://www.gssiweb.com 6/03/05.
(2) Carmichael, C, et al. Food for Fitness, 1st edition. New York: Berkley Books, 2004.
CAPTAIN BARTLEY J. WARD
354 FS
Davis Monthan AFB, AZ
