Back to Sports Corner Hydration, Diabetes, and Sports Performance

Is dehydration anymore of a concern for someone with diabetes? Athletes with diabetes may be more prone to dehydration when blood sugars are running high due to increased urine production. Adequate hydration is important for anyone before, during and after competition. Dehydration means the body is undersupplied in body fluids. It can be caused by losing too much fluid, not drinking enough fluids or a combination of both. Individuals with diabetes are more likely to become dehydrated when blood sugars are higher than normal. Exercising on a hot day can compound the problem. Blood volume is decreased from the sweating that takes place during exercise in a hot environment potentially causing at minimum decreased performance but possibly an individual to faint. Children are more at risk for dehydration because they tend to get hotter during exercise (higher heat gain due to more skin surface compared to body weight), sweat at a lower rate, adjust to extreme temperatures more slowly, and they have a heart that pumps less blood.

Signs and Symptoms of Dehydration

Many athletes wait until they are thirsty before consuming any fluids. At that point it may be too late and performance can suffer because the thirst mechanism in the body is not activated until 1-2 percent of body weight is already lost due to fluid. The best way to tell if dehydration has set in is to look for the color of the urine. If it is dark and yellow there is a good chance an athlete is dehydrated. Although, some supplements (i.e., vitamins) may cause a darkening of the urine so be aware of that. The quantity of urine or lack there of may be a sign of dehydration too. Ideally, having a normal amount (specific to the individual) and light yellow or clear coloring will indicate proper hydration. A dry or sticky mouth can be a symptom as well as sunken eyes and being lethargic. It is also important to note the some of the symptoms of dehydration (i.e., lethargy) may be confused with a low blood sugar. It is important to check blood sugars to rule that out.

Muscle cramps can be a symptom of dehydration. It is not unusually for an athlete to cramp up during a very hot day. Lack of sodium in the body may be a cause of muscle cramps too. Female athletes who eat a lot of salads tend to lack sodium in their diets so cramping may be a concern. Other electrolytes such as, potassium, chloride will need to replace for activity lasting longer than one hour.

Dehydration and Performance

Participation in sports in a dehydrated state will unquestionably decrease performance. In fact, a loss of 1 to 3 percent of body weight due to dehydration has been shown to impair sports performance. A 165lb athletes losing 2-5lbs during activity is enough to decrease performance and possibly mean the difference between victory and defeat. As most athletes know during hot weather, dehydration is more likely to occur. Interestingly, individuals on low carb diets may be more likely to become dehydrated due to increased fluid loss.

There has been some press over the past few years about marathoners who have over hydrated during a race. In fact, there was a runner in the Boston marathon several years ago who died from this condition. This is rare, but the condition, called hyponatremia, results from a combination of abnormal water retention and sodium loss. Most of the cases centered on slow runners (5+ hours of running) who constantly drank water thinking they needed it. Although almost everyone reading this article will not be affected, it is important to know for people running a marathon, a slow one at that. Hyponatremia can be prevented by drinking water combined with sodium (i.e., sports drink).

Water vs. Sports Drinks

Typically, activities under one hour, water is sufficient to maximize performance. Participating over an hour sports drinks can be helpful to athletes who are exercising at a high intensity. There are two reasons to use sports drink for longer activity. The first is for the calories (i.e., carbs) needed to continuous activity which is 15 grams for every 30-60 minutes of exercise. Secondly, to replace the loss of sodium, potassium, and calcium during prolonged exercise.

Occasionally athletes will consume sodas before a game maybe even to bring up a low blood sugar. Caffeinated beverages such as sodas, coffee, and tea act as diuretics and increase urination which leads to dehydration. For best performance caffeinated beverages are discouraged. Coffee has been used as an ergogenic aid to help increase endurance but dehydration is a risk.

It has been shown that sports drinks are consumed more readily in kids than water. In fact, one study show kids voluntarily consumed 90% more fluid when a sports drink was used compared to water. An athlete with diabetes must weigh the risk benefit of using sports drinks solely for hydration. If an athlete has a high blood sugar (300 mg/dl+) before, during, or after activity water should be used to help flush out possible ketones as well as aid in hydration.

Recommendations for Peak Performance

Our bodies need a minimum of four 8 oz glasses of fluid intake a day. Requirements will vary with age and activity but athletes need 2-3 times the minimum amount or 8-12 eight oz glasses. Sports more aerobic in nature (i.e., cross-country, basketball, soccer) will require amounts on the high end. It an athlete takes less than what the body needs or lose more during activity the end result is dehydration and poor performance.

The American College of Sports Medicine position on hydration during exercise is to start drinking early and at regular intervals in an attempt to replace fluid lost at a rate sufficient enough to replace the water lost during sweating or consume the maximal amount tolerated. The possible ambiguity to that statement is that very few athletes actually weigh themselves before and after activity to determine how much water weight was lost. A good rule to follow is to drink two glasses (16oz) two hours prior to activity, one glass (8 oz) an half hour to an hour before and 4-6 oz every 15-20 minutes during activity. If an athlete is able to weigh themselves before and after activity replace 16 oz of water for every 1 percent of body weight loss due to sweating.

Cold water is better than warm water. Cold water is absorbed more quickly from the stomach into the system. Another benefit of cold water (40-50 degrees F) is cooling the core temperature of the body during hot days. Many coaches and dietitians recommend diluting sports drinks by 50% for optimal performance. For the athlete with diabetes the carbs must be taken into account when consuming sports drinks. For instance, an 8oz cup of Gatorade has 14 grams of carbs whereas, Powerade has 19 grams. Those numbers are cut in half if it is diluted by 50%. When drinking for performance the 5 gram difference may not be a major factor but when blood sugar plays into it after a couple of cups it will. A sports drink with 4%-8% carbohydrate is recommended for replacement during and after exercise, specifically when the exercise is longer than one hour.

Rick Philbin, MBA, M.Ed., ATC

February 2006

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Last Updated: Friday September 07, 2012 11:17:20
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