Whether it’s hot spinning in Los Angeles, scorching boot camps in NYC, or heated boxing classes, roasted versions of top workouts are everywhere. In fact, the owners of Sweat Shoppe indoor-cycling studio in LA phased out regular classes because of the demand for hot.
Olivia Lambert was hooked after her first hot ride. “I sweat so much, it’s like I’d been cleansed,” says the 25-year-old account
That’s a common belief, but it’s not scientific. Your kidneys and liver — not your sweat glands — are what filter toxins from the body.”The point of sweating is to cool you down,” says Dee Anna Glaser, M.D.,who has studied excessive sweating. In fact, she warns,”if you don’t drink enough water to compensate, you put stress on your liver and kidneys and they can’t do their jobs.”
Nor does a hot workout torch more calories. “Intensity is the best indicator of calorie burn — not sweat or heart rate — and most people lessen intensity when exercising in heat,” says Douglas Casa, Ph.D., director of athletic training at the University of Connecticut. Even if you could match intensities, you’d burn at most 10 percent more calories.
What adding heat can do is pump up performance. Cyclists did better in both cool and warm environments after training in hot temps for just 10 days, a study in the Journal of Applied Physiologyreveals. “When you get hot, blood vessels in your skin dilate to stimulate sweat,” says study author Santiago Lorenzo,Ph.D. “Once you’re acclimated, you sweat more and sooner. Your skin needs less blood to cool you off and more can be sent to muscles and organs.” This increased blood flow keeps muscles flexible, boosts endurance, and makes exercising in cooler temperatures feel like a cinch. Lambert says doing hot spinning a few days a week helped her cut 25 minutes off her marathon time. “Everything else felt easier,” she says.
Hot fitness can also be pretty damn motivating. It can take a while to see exercise results, so small visual cues that prove you’re making a difference are helpful. “The emotional component of finishing a workout drenched is incredibly rewarding,” says Lorenzo.
Bottom line: If hot fitness seems like torture, there’s no health reason to do it. If you love sweating buckets or are in training, go for it.