The Chicago "hydration therapy" clinic IVme advertises intravenous fluids to athletes to improve performance.
A $169 pre-race IV can help marathon runners "avoid cramping and 'hitting the wall,'" according to the company's website. After the race, IVme suggests, a sudden flood of fluids can help with recovery.
But experts say the infusions are not only risky but likely to slow a runner's pace — as well as creating an urgent need to stop at a portable toilet.
"You'd be heavier because you have more mass to carry and need to pee pretty soon afterward," said hydration researcher Paul Laursen, the physiology manager for High Performance Sports New Zealand. "You'd also be putting yourself at risk of hyponatremia because you'd have more water in your bloodstream relative to salt."
Still, professional athletes — including runners, triathletes, cyclists and tennis players — are increasingly using IVs for recovery. Chicago Fire defender Bakary Soumare said he makes a visit to IVme when temperatures are over 90 degrees and he plays several games in one week.
"I do it two days before or two days after (a game)," he said. "For me, it's part of my regimen as a soccer player, like stretching. The body loses so much water; it's the fastest way to put it back."
Dr. Jack Dybis, medical director of IVme (formerly named Revive), said he has seen the IVs benefit endurance athletes, though he acknowledges the evidence is anecdotal.
"If you fill up the tank and top it off before you do a race or play football or soccer, you won't cramp up as much and you're not bloated," said Dybis. "A sports drink takes time to get into the system, whereas the IV goes directly into the blood system and the kidneys. We're not saying it's for everyone, but in certain cases it is helpful."
Laursen said cramping is likely related to fatigued muscles, not dehydration. Nor is lack of fluids responsible for the wooziness that athletes experience when they "hit the wall" or "bonk" during a race. The cause of that is low blood sugar, and ingesting more carbohydrates can help, Laursen said.
Tim Noakes, a professor of exercise and sports science at the University of Cape Town in South Africa, called the IV treatments "brilliant marketing."
"Why not just drink the stuff?" he said. "The end result will be the same — expensive urine."