Fluid for Thought


Do you ever wonder how much fluid is needed to prevent dehydration? If you’ve experienced dehydration, you know it derails swim performance and causes other effects such as tiredness, headaches and confusion or poor judgment. 

Fluid is the overlooked “magic bullet” for swimmers and one of the best ways to optimize swim performance. 

Not only is it important to drink, it’s important to drink enough. Experts suggest that 2% dehydration (2 pounds weight loss in a 100-pound child) negatively impacts athletic performance. 

According to the Institute of Medicine (IOM), young athlete’s thirst should be the gauge or indicator for how much fluid to drink. Research also suggests, that if youth athletes are given the opportunity to drink during exercise, the thirst mechanism will allow for adequate fluid intake so they meet their hydration needs. 

But if you want numbers, here are the latest recommendations for child athletes: 

To prevent dehydration, child athletes should drink 6 ml per pound of body weight per hour (100# young swimmer needs 600 ml or 20 oz, per hour). Drink this amount 2-3 hours before jumping into the pool and during exercise. 

To replenish fluids after exercise, drink 2 ml per pound of body weight per hour (100-pound child swimmer needs 200 ml per hour or ~7 ounces, per hour). Drink this amount 1-2 hours after exercise—it promotes adequate hydration status for the next exercise session. 

Water and other beverages can help satisfy the hydration needs of the swimmer. Many parents already know that it isn’t wise to offer up sugar-sweetened beverages like soda and sugar-added fruit juices routinely throughout the day. These drinks may help keep swimmers hydrated, but they can have a negative impact on overall diet quality. 

Most importantly, the choice of fluid should be something the swimmer likes to drink, as drinking adequate amounts is critical. 

Sports drinks are perfect for the long workout (greater than 1 hour in duration), and provide sugar, fluid and electrolytes to help beat dehydration. And they are effective! Because they are flavored, they encourage drinking. It’s best to keep their role limited to the pool, though. 

Here are a few other beverage guidelines that will help prioritize the young swimmer’s health and swim performance: 

GOOD: 100% real fruit juice (maximum of 1 to 1 ½ cups per day). Infrequent use of sugar-sweetened beverages.

BETTER: Milk, or calcium/ Vitamin D- fortified milk substitutes (aim for 3 cups per day).


BEST: Drink water, more than you think! The bulk of beverages should be from water. Use Sports drinks wisely and target their usage around workouts and race day. 
It’s a mistake to think that just because swimmers are in the water, they get enough fluid. Coaches and parents have an opportunity to train young swimmers to drink regularly and make good choices. Good hydration habits are learned in and around the pool—maximize this asset for great performance! 

Jill Castle, MS, RD, LDN is a registered dietitian and child nutrition expert. She is the owner of Pediatric Nutrition of Green Hills and creator of Just The Right Byte, a child and family nutrition blog. She lives with her husband and four children (one swimmer!) in Nashville, TN.