I’ve studied hydration for almost 20 years, mostly from the lens of overhydration. So, every time a coach or trainer instructs athletes to “stay hydrated” or “drink more water,” my heart sinks.
Drinking too much water can cause brain swelling, which can lead to confusion, seizures, coma and death. Overhydrated lungs can fill up with fluid, leading to breathing difficulties and respiratory distress. Muscle cells rupture from cell swelling, which can accelerate kidney damage. Although we all need to drink water (or fluids in general) before, during and after exercise, too much of a good thing can be deadly—especially when it’s hot. This is my science brain talking, sensitized by thousands of water intoxication cases I’ve witnessed in person and through case reports crossing my desk.
My science brain, however, recently came in conflict with my tender human heart on a recent Friday. It was a hot and humid day in Detroit, and the sun was beating down on our football guys as they ran 110s across the field. I have been monitoring football player heart rates at Wayne State University for three years and have come to know—and love—these fierce but gentle giants. Our boys were clearly suffering in the high heat and humidity, and I felt powerless to help them.
I now understood why coaches, trainers, parents and well-intentioned spectators shout “Stay hydrated!” and “Drink more water!” as I found myself running across the field, carrying water bottles, desperately trying to ease their pain. I felt the need to protect them from all the evil consequences that high heat, humidity and intense physical activity can unleash. “Football players die from heatstroke and overhydration,” my science brain warned, especially during August football camp.
Water replacement is our savior but can also be our enemy when it comes to exercising in the heat. The detrimental effects of dehydration on health and performance are widely promoted. The deadly effects of overhydration are lesser known. The key to proper hydration is moderation, while avoiding both extremes. The problem with athletes, however, is that they are taught to push beyond their limits of tolerance. This is why we well-intentioned adults might need a little refresher to ensure that our athletes remain safe during summer training. Here are a few tips to remember:
Have a variety of fluids freely available on the sidelines such as water; sports drinks that contain electrolytes, such as salt; and something sweet that contains carbohydrates to sustain blood sugar levels. Allow athletes to drink whenever they’re thirsty, but avoid forced drinking. Remember that most of our fluid needs are replenished during meals and that all beverages and foods (especially fruit—we like watermelon!) count toward our overall water replacement needs.
Pour water over your head
Pouring water into your mouth works, but over your head enhances evaporative cooling. The cooler the water, the better!
Ice, ice baby
Drinking ice slushies may help lower body temperature. Putting ice on your head under a hat or cap, using ice bandanas or cold towels on your neck and dipping your forearms in ice water can also enhance heat loss.
Don’t “hold the salt”
Sweat is salty, so eating salty snacks, such as pretzels, will help replace sodium losses while enhancing water retention.
Take it slow
It takes 14 days to fully acclimatize to the heat. Slowing down your exercise load or pace reduces metabolic heat production and eases the strain on the cardiovascular system.
My human heart agrees that “stay hydrated” and “drink more water” is good advice. But my science brain always wants to add, “just don’t overdo it.” Stay safe!
Tamara Hew-Butler, DPM, PhD, FACSM, is an associate professor of exercise and sport science at Wayne State University in Detroit. She directs the Warrior Performance Human Research Lab, and her scientific interests include hydration and sports performance.