Fluid Balance BasicsQ: I have heard that drinking as much water as possible the day before a race is a good way to make sure your body is fully hydrated for racing. Is this true? A: The amount of fluid and sodium the body retains is carefully controlled by the kidneys. In order to maintain a certain level of sodium in the bloodstream, the kidneys will release extra water as urine if the sodium level becomes diluted, and falls. Excessive amounts of sodium free fluids such as water will ultimately mean more trips to the bathroom and may cause sodium levels to fall too low if a large volume of water is ingested over a short time period. Gradually the kidneys will begin to retain more sodium so that balance is restored. This gradual readjustment works fine while at athlete is at rest. During exercise, however, sodium losses may be significant. Symptoms of sodium depletion, a.k.a. hyponatremia, include excessive fatigue, bloating, confusion, and disorientation. Blood levels of sodium that drop too low can lead to coma, seizures, and death. Q: I read that additional sodium in the days leading up to an event may be a good way to “stockpile” levels so you’re not depleted on race day. A: Most athletes get plenty of salt, or sodium in their usual daily diet, howeverduring periods of acclimatization to hot temperatures sodium losses may be higher than normal. To insure adequate sodium intake to cover losses in sweat, then eating salty foods or adding table salt to foods is recommended. This does not mean you have to go crazy with the salt shaker the night before a race. A sodium load can rapidly increase fluid retention and may cause heart failure insusceptible individuals as well as significant bloating. Research has shown that optimizing fluid reserves the day of the race can be done by consuming a meal with sodium about 4 hours before a race, followed by a beverage with a high sodium level about 2 hours before the onset of exercise. Q: If the race is “on”, can I assume it is safe to for me to participate? A: Races are rarely cancelled due to the weather, and that includes a heat wave. If you haven’t been training in the heat, then your sodium loss will be about 50% higher than if you were acclimated to high temperatures. And if you are not in shape for the race, and have not been training in the heat, you will lose almost twice as much sodium per liter of sweat. Being trained and acclimated for conditions is a critical factor when it comes to tolerating exercise stress in a hot environment. Race responsibly, and know your limits. Q: Does pickle juice relieve muscle cramps because it is high in sodium? A: A 2-1/2 ounce dose of pickle juice brine has been shown to reduce the duration of muscle cramps. Why it works is still a matter of debate, however, studies have shown that the sour tasting juice does not change plasma sodium levels. Researchers speculate that the effectiveness of pickle juice in providing relief is possible due to the effect of a nervous impulse stimulated by the vinegar on tired muscles. Q: Do I get muscle cramps during exercise because of low sodium or potassium levels? A: Despite the popular theory that exercise induced muscle cramps are caused by sodium or potassium deficits, recent studies have suggested otherwise. While the actual cause of muscle cramps is still hotly debated, in a recent study on Ironman triathletes researcher found there was no difference between athletes who cramp vs. non-cramping in pre-race or post-race serum electrolyte concentrations and body weight changes. Several studies have found that the development of muscle cramps was associated with faster actual race times, a history of muscle injury, or a history of previous muscle cramps.
Tips for racing in hot weather
- Start exercise well hydrated
- Know how to dress for the weather
- Consider alternate cooling strategies (besides sweat): iced t-shirt, wet hair, visor
- Have a fluid and sodium replacement plan