Going the Distance? Hydration and Exercise

I could write all day long touting the various benefits of exercise. It's important to establish an exercise regimen because physical activity offers many health benefits, including decreasing blood pressure, increasing muscle strength, lowering blood fat levels (cholesterol and triglycerides), improving sleep, decreasing stress, increasing insulin sensitivity and helping control body weight.

For endurance athletes, including triathletes and marathon runners, it's critically important to hydrate, replace electrolytes and fuel your body. You may not realize that the kidneys are responsible for managing most of these nutrients and for regulating fluid levels in the body, but they play a crucial role in efforts to go the distance. Your kidneys not only help you cross the finish line, but they can be prone to injury during endurance events if you don't take care of them.

Most people need to be aware of the risk of dehydration, or fluid depletion. Kidneys regulate the body's water volume by controlling sodium levels and regulating electrolyte balance. Typically during exercise sessions of over 90 minutes, sodium and many electrolytes leave the body through sweat and urine. People often replenish the fluid losses with water, but this doesn't correct for the sodium and potassium losses. Your body needs sodium for fluid balance, blood pressure control, as well as the nerves and muscles.

It's not only dehydration that you should be concerned about. Water "overload" or hyponatremia can cause confusion and sometimes seizures. In fact, an article in the New England Journal of Medicine underscores just how prevalent this danger is for runners. Thirteen percent of people participating in a marathon were shown to have developed hyponatremia which can also cause nausea and vomiting, dizziness, headaches, short-term memory loss, muscle weakness and even comas. Hyponatremia results when the sodium level in the blood is below the normal range of 135 to 145 milliequivalents/liter (mEq/L).

Exercise, running and other endurance activities are an important part of overall good health, but it's important to protect your kidneys when being active. As running season heats up, cool down and take care of your kidneys with these tips:

1. Remember the 90+ rule. Consume a balanced electrolyte solution if your activity lasts longer than 90 minutes. Take drinks and shot blocks that have sodium, electrolytes and carbohydrates. Replace sodium and other electrolytes in a balanced way, so don't only drink water, or just use electrolyte supplements. Studies have suggested that some modest weight loss during long distance running is desirable. You should not gain weight during extended exercise. It is important to weigh yourself before and after training exercise to gauge the proper amount of water and electrolyte containing fluids to drink.



2. Avoid NSAIDs before and during your activity. A problem for endurance athletes is acute kidney injury (AKI), and taking nonsteroidal anti-inflammatory drugs (NSAIDs) places you at increased risk. These over-the-counter pain medications have been shown to damage the kidneys over time and this effect is heightened during heavy exertion, especially when your fluid levels are depleted.



3. Keep peeing. Yes, how much you're peeing is important. Typically, the best way to assess how well your kidneys are handling your activity is if they are continuing to make urine. If you are peeing regularly, then that is a sign that you are taking in enough fluid, and that the kidneys are still processing these fluids adequately. This is especially important in the heat, as dehydration is common during exercise, and particularly prolonged exercise.

For more information about the kidneys, visit the National Kidney Foundation at www.kidney.org.

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