There’s a ton of misinformation about how much to hydrate and when, but the basics are actually pretty simple. Here’s what you need to know.
Robert Sallis has seen it all. As a medical director for the Ironman World Championships in Kona, Hawaii, he’s spent 20 years watching athletes in every manner of distress get wheeled into the medical tent. He’s seen hyponatremia, or overhydration, a handful of times. He’s seen hundreds, maybe thousands, of dehydration cases. Sallis has even seen athletes show symptoms of both at the same time: they’ve dropped weight over the course of the race, signaling dehydration, but their blood sodium levels are dangerously low, a sign of hyponatremia.
What most surprises Sallis, a former president of the American College of Sports Medicine, is the heap of misinformation on hydration that he hears swirling among athletes. He partially blames the media that picks up stories like this Cycling News article from December 2016, in which Roger Palfreeman, Team Sky’s top doctor, touted “functional dehydration” as a strategy for making his athletes lighter and thus faster. “It’s stupid,” says Sallis, adding that mental and physical performance plunges when you’re 2 percent dehydrated—any advantage from a reduction in weight would likely be offset by a reduction in power and mental resolve.
Advocates of functional dehydration tend to cite two athletes in particular to support their position: Tour de France rider Tommy Simpson and marathoner Jim Peters, who was a lifelong proponent of abstaining from food and water during races. “There is no need to take any solid food at all and every effort should also be made to do without liquid, as the moment of food or drink is taken, the body has to start dealing with its digestion,” Peters said in 1957. According to Sallis, both athletes experienced extreme, career-ending cases of heat stroke because of this strategy. Simpson, known for trying to ride long stages with just a few bottles, died in 1967, likely from a combination of heat stroke and amphetamines, after collapsing during a scorching climb up Mont Ventoux.
But there is a lot of new, thorough research on the rules of hydration, and these rules could save your life. Learn them, and then practice them. Here are the basics.
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