HYPONATREMIA IS A SERIOUS THREAT ON HOT, HUMID DAYS
Hot, humid weather poses a serious health risk to all athletes and fitness enthusiasts who engage in strenuous activity for long periods of time. Most individuals are now programmed to replace lost fluids with properly spaced water consumption during activity. Athletes are aware that once a water deficit occurs. it is nearly impossible to eliminate until the post-exercise period. They are also aware of the tremendous amounts of fluid that is lost through perspiration during several hours of tennis, jogging, road racing, triathlon and marathon races, soccer, rugby, and othe team sport activities. This behavior provides considerable protection from the common heat-related disorders such as muscle cramps, heat exhaustion, and heat stroke.
Unfortunately, it is not entirely the correct behavior to prevent a lesser known heatrelated disorder that could be affecting your daughter.
Drinking large amounts of water and failing to consume sufficient sodium (also lost in perspiration) can lead to a condition known as hyponatremia. This disorder results from losing large amounts of perspiration (sodium and water) and consuming replacement fluids with an inadequate concentration of sodium. The dilution of the sodium content of the blood (the more water consumed, the greater the dilution) leads to reduced blood volume which then produces the signs and symptoms of hyponatremia, some of which your daughter is exhibiting: bloated stomach, confusion, cramping, headache, nausea, and swollen fingers and ankles. The condition can become serious and lead to seizures and coma.
To avoid both heat-related disorders associated with dehydration (muscle cramps, heat exhaustion, heat stroke) and blood sodium imbalance (hyponatremia), athletes should follow the prevention strategy below.
1. Hydrate properly before a tennis match, competitive event in any sport, or practice session. Since dehydration is still more common than low blood sodium, it is wise to begin each exercise session well hydrated. Do not rely on thirst as your guide. One strategy is to drink 1/2 liter (slightly more than one-half quart: 1/2 liter = 500 ml., 1/2 quart = 475 ml.) of water about 1 to 1/1/2 hours prior to exercise; then sip on 1/2 cup (4 ounces) every 10 minutes to maintain hydration.
2. Replace lost fluids and sodium continuously during activity. Once exercise begins, replace lost fluids immediately by consuming a sports drink with sodium and other electrolytes at frequent intervals. Be aware that, on a hot, humid day, your daughter can lose as much as 1 liter of sweat per hour. The sodium content of sweat ranges from 2.25 – 3.4. grams per liter and can mount quickly in a long tennis match. Remember that without adequate fluid, blood volume will drop quickly. Replacing 1 liter of sweat loss per hour is not easy and requires four 8-ounce cups per hour, twice that amount to replace 2 liters. If your daughter can eat during a workout or match, she should choose salty foods such as pretzels.
3. Rehydrate immediately after the match or practice session. You can identify the amount of fluid deficit by recording nude weight before and after exercise. One liter of water weighs 2 pounds, one pint weighs about 1 pound. For every pound of body weight loss, one pint (16 ounces) of water should be consumed immediately. If body weight is down 2-3 pounds, 32-48 ounces of fluid (with adequate sodium) should be consumed within the next hour. At this point, an athlete is also now aware that they failed to replace fluid losses during activity by 32-48 ounces. Adding 32-48 ounces to the fluid ounces actually consumed during the exercise session will determine the total amount that was actually needed. By recording the actual fluid needs and exercise time, your daughter will have a better idea of how much she needs to drink during activity on the next occasion for complete replacement.
4. Avoid NSAIDs (aspirin, ibuprofen) and other substances that induce a diuretic effect. The prevention strategy should solve the problem on most days; however, on an extremely hot, humid day, a 3 hour plus tennis match and a player who perspires profusely places a heavy demand on the body’s heat regulation system. Athletes must therefore be aware of the signs of heat-related disorders and stop activity before symptoms progress to the serious stages