March 5, 2024

It’s summertime and the sweating comes easy for children. Whether they are enjoying a pickup game of basketball or competing at a sports camp, how does a parent know the appropriate amount of liquid refreshment to offer?

Part of the mystery lies in whether the child’s body produces a lot of salt while engaged in a difficult workout.

Staying Hydrated During Exercise

Brendon McDermott
Brendon McDermott

Staying hydrated and avoiding heat illness are two areas Dr. Brendon McDermott at The University of Tennessee at Chattanooga understands, and he is often asked about his research in this area. McDermott, Assistant Professor, Clinical Coordinator for Graduate Athletic Training Program and Co-Director of the Applied Physiology Laboratory has one overarching goal: to prevent heat related deaths, particularly in athletes.

One of McDermott’s current studies focuses on student athletes who cramp during intense movement, creating an extra layer of exercise performance frustration. There are two prevailing theories about the cause of cramps.

Some researchers believe those who produce higher amounts of salt when they sweat harbor an electrolyte imbalance which initiates a cramp, while others blame neuromuscular fatigue.

By measuring the sweat and salt outputs of students who cramp compared to a control group who doesn’t, with common factors like age, , and similar levels of activity, McDermott hopes to unravel this painful mystery.

Even if your child has not complained of cramping while exercising, there are some tips to keep in mind. Hydration guidelines have evolved for the average person, but who exactly is the average person? Each body reacts differently and replenishment needs depend upon the individual, according to McDermott.

How To Figure Out Sweat Rates

“Sweat rate is very simple to calculate: weigh yourself before exercise, with as little clothing as possible; exercise for a half an hour and don’t drink or use the bathroom for that half hour; weigh yourself again, wearing the same amount of clothing to see how much you’ve lost,” McDermott said.

To get a true picture of sweat rate, this test should be done in the cold, in the heat, at different intensities of exercise. It will then be easier to gauge whether your child is a heavy or light sweater.

If that sounds like a lot of work there’s a quicker way to assess hydration needs, and it’s focused on the delicate matter of, ahem, passing a different kind of water.

“You can monitor your urine color. It should have a light yellow tinge to it. Lemonade is much better than apple juice. And if you’re delving into the iced tea realm, it’s time to drink. It’s normal to have darker urine in the morning,” McDermott said. “As for frequency, some people are camels, other people urinate frequently.”

McDermott explains body size is not the main factor in sweat production. During his training for an Olympic marathon, accurate measurements showed Alberto Salazar lost nearly 10 pounds of water an hour. He only weighed 145 pounds.

“When you’re talking about a football lineman who loses 10 pounds of water, that may not be so bad, but for someone who is 145 pounds, that’s a huge percentage,” McDermott said. “If someone is losing 10 pounds of water per hour and they are told to replenish with 16 ounces of water, that’s one pound, and one-tenth of what you are losing in an hour—that’s insufficient.”

Similarly, young children at sports camps, especially those who wear heavy pads for long periods of time, can be at risk. Water is not enough to replenish what some athletes lose in sodium and calories, so many reach for full strength sports drinks.

Hydration tips for kids

1. Those involved with physical activity should assess their personal sweat rate
2. The goal is to replace what is lost (no more, no less)
3. Activity longer than one hour most likely requires fluids, electrolytes, and carbohydrates in liquid or solid food forms
4. Exercisers should begin exercise well hydrated
5. Fluids should be readily accessible during activity
6. Following activity, it is important to rehydrate as soon as possible (within 30 minutes)
7. Cool temperature rehydration fluids encourage fluid consumption in the heat
8. Monitor hydration status by checking urine production and color

It’s important for everyone to be well hydrated before exercise begins, but too much water could lead to hyponatremia.

“In the most severe case of hyponatremia, those who have taken the advice to drink as much as they can tolerate during a marathon, they drink at every rest stop, and there have been cases where people have gained up to twelve pounds after running a marathon in order to avoid dehydration,” McDermott said.

Finally, drinking when you feel parched is not a good way to gauge hydration needs, because the thirst mechanism does not kick in until a person is two percent dehydrated.

“It’s okay if you are a healthy person who is used to working out in the summertime—it’s a great way to prevent hyponatremia,” McDermott advised. “But if you are a competitive athlete, you’d be behind the game and trying to play catch up. Think again about those like Alberto Salazar. If they drink to thirst, they’re two percent behind plus they must replace ten pounds an hour.”

In addition to his responsibilities at The University of Tennessee at Chattanooga, Dr. Brendon McDermott serves on the medical and science advisory board of the Korey Stringer Institute, founded by Kelci Stringer to “minimize sudden death in sport for any reason, beginning with exertional heat stroke.” Kelci’s husband Korey Stringer, a Minnesota Vikings offensive lineman, died from exertional heat stroke in 2001.


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