Defeating the Heat on Race Day

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Anyone who has raced the Ford Ironman World Championship in Hawaii knows that the environment is not very forgiving, with average air temperatures on race day ranging from 82 to 95 degrees, humidity levels hovering around 90 percent, and radiating heat off the black lava fields sending temperatures on sections of the course in excess of 115 degrees. As a result, some of the most memorable images of the Ironman are of athletes staggering towards the finish line and ultimately being treated for a fluid and electrolyte imbalance in the medical tent. This article explores the nutritional strategies that will allow you to defeat the heat and celebrate your successful journey down Ali’i Drive to that coveted Ironman finish.

Adapt to the heat 

Heat acclimatization is a process by which the body makes adjustments to promote better cooling in hot environments with full benefits being seen after 10-14 days. Early adaptation can start to occur after a few days and include conservation of sodium chloride as well as other minerals important for muscle function and fluid balance, expanded plasma volume, lower heart rate, and ultimately a reduced rating of perceived exertion as a result as the decreased stress being placed on the cardiovascular system. Unfortunately, spending two weeks in tropical heaven leading up to Ironman race day is not realistic for many athletes and thus it is important to spend as much time as possible training at the heat of the day or simulating an environment similar to the forecasted race conditions. 

Complete an environment-specific sweat test 

As discussed in previous articles of mine, a sweat test entails that one weigh in immediately prior to and post training and monitor fluid intake during the workout. Think of each pound lost as a pint of fluid and 200-500 mg of sodium. Dr. Doug Hiller, an orthopedic surgeon who has studied sweat rates in Hawaii Ironman competitors, has found that triathletes competing in Hawaii will lose on average one to eight pounds each hour during the event. The goal is to remain within two percent of your pre-race weight to avoid performance declines associated with dehydration although certain environmental conditions, like that found in Kona, will make this feat hard for heavy sweaters unless pace is moderated; as physiologically, there is a cap to how much fluid the human body can actually absorb.

Be aware of your body's ability to absorb fluids

Once sweat rate is determined, at the other end of the spectrum is determination of actual uptake rate (how much can you absorb), which research suggests falls just over a liter per hour for most athletes. Monitoring the amount of fluids voided (how many times you pee during your workout) as well as the color of urine can be helpful in determining how efficiently fluids are being absorbed. Urine that runs pale yellow is healthy but a clear color generally indicates fluids are not being absorbed. The risk that is run from overdrinking is hyponatremia (low blood sodium) that is driven by exertion-based losses of sodium in sweat as well as a dilution effect with excess fluids. Common symptoms associated with hyponatremia include a sloshy gut, bloating, headaches, clear urine, weight gain, and vomiting. If symptoms arise, it is important to taper back or stop fluid intake and in warm conditions, slow down to slow exertion-based losses of sodium while eating sodium-rich foods (e.g. pretzels, salt packs).

Avoid nonsteroidal anti-inflammatory drugs (NSAID) race week, including race day 

Yes, this means Ibuprofen and while the anti-inflammatory benefits of this drug are very alluring when logging 15+ hours a week of training in preparation for Ironman, use should be reserved for post-race as Ibuprofen's role in inhibiting prostaglandins can alter the body's ability to move fluids through the kidneys and exacerbate risk for dehydration, hyponatremia, and renal failure. Concerned about muscle soreness? A proper warm-up prior to canon start will be far more helpful in muting muscle soreness and potentially save a trip to the medical tent later in the day.

Practice salt loading 

Salt loading is a relatively new concept, but over the past five years, there have been a handful of studies producing promising results for the endurance athlete with regards to both performance and protection against hyponatremia. One study published just last year demonstrated that ingestion of 25 ounces of concentrated sodium beverage (2.8 grams) in the 105 minutes leading up to a run helped increase blood volume, allowing the athletes to maintain a lower core body temperature and a lower level of perceived effort. Similar results with the addition of increased exercise capacity have been demonstrated in female cyclists consuming 20 ounces of a concentrated sodium beverage (2.3 grams) in the 105 minutes leading up to a submaximal cycling effort in warm conditions. It is important to note that athletes are naturally exposed to sodium-rich foods (e.g., pretzels, bagels, tomato sauces, chips, sports drinks) and may not need to add extra salt to their normal pre-race routine. Triathletes with pre-existing elevated blood pressure should check with their physician before practicing salt loading.

Fluid Imbalance Defined 

dehydration: Excessive loss of body water with significant performance declines being demonstrated with more than two percent body water loss. Risk of heat stroke being demonstrated with 10 percent body water loss. Symptoms include increased thirst, dry mouth, weakness, lightheadedness, and darkening of the urine or decrease in urination.

hyponatremia: An abnormally low concentration of sodium in the blood generally caused by drinking in excess of ability to absorb, exertion-based losses of sodium that are not replaced, and use of NSAIDs. Symptoms include bloating and puffiness in the face and fingers, nausea, vomiting, muscle weakness, headache, and disorientation.

Gearing up for an Ironman and want nutritional guidance from an expert? Kimberly Mueller, MS, RD, owner of Fuel Factor Nutrition, is a Registered Dietitian, Exercise Physiologist, and triathlete who provides nutrition coaching, race-nutrition guidance, and customized meal planning to athletes worldwide. More information on Kim's services can be found at www.Fuel-Factor.com. Kim can be reached at kim@Fuel-Factor.com.

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