Your Health Lindsay Guinaugh | 7 years ago

Thirsty? Hydration Is Key to Running Performance

Most runners know dehydration negatively impacts endurance performance. But overhydration can be just as dangerous for long-distance runners. So whether you're running a sprint or a marathon, maintaining balanced hydration is essential to a successful run.

By: Catherine Rainbow, MD Carolinas HealthCare System’s Sports Medicine & Injury Care


Dehydration in runners can come on suddenly or creep up slowly. Acute dehydration generally occurs in two to three hours and is most commonly seen in endurance athletes. Chronic dehydration is both less visible and more dangerous than acute, and usually results from several consecutive days of inadequate fluid intake. Fluid loss as little as 1 to 2 percent of a runner’s total body weight can elevate core body temperature and have a negative impact on performance. Dehydration greater than 3 percent of body weight further disrupts balance and, because the production of sweat decreases, the risk of heat illness increases. Remember, thirst is not a gentle reminder to hydrate, it’s a warning sign that severe dehydration has set in – the sensation of thirst typically starts at body weight loss of 5 percent or greater. At 6 to 10 percent loss of total body weight, the heart begins pumping less efficiently, leading to lower sweat production and reduced blood flow to the skin and muscles.

You may be dehydrated if you experience: - Thirst - Decreased skin elasticity - Infrequent urination - Headache - Weakness - Decrease in body weight between pre- and post-exercise weight (more than 1 percent)


Overhydration causes hyponatremia, which occurs when water consumption dilutes salt concentration in the body, creating a low salt level in the blood stream. This is most common in marathon participants who mainly drink water during competition.

You may be overhydrated if you experience: - Nausea - Lightheadedness - Lethargy - Cramps - Generally feeling “off”

If you’re a long-distance runner, make sure to take in enough salty foods and beverages to keep your body balanced, and alternate water with sports drinks.

How to Stay Balanced

Don’t wait until you’ve begun exercising to start hydrating. By then, you’re already behind! Drink fluids four hours prior to the start of your activity and again at two hours out. Water is an excellent source of fluid for activities lasting less than an hour. However, athletes exercising longer than an hour should consume a sports drink.

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