Squeezing any physical activity into a hectic schedule is commendable, but does a toasty warm environment make a difference? Before attempting to maintain a solid dumbbell grip with sweaty palms or slip-‘n-slide down a sopping yoga mat, find out whether hot workouts are worth wringing your clothes out for.

Some Like It Hot—Why It Matters

To up the ante on their sweat quotient, exercisers can choose to take their workout to a hotbox. Some gyms now offer 80-100 degree versions of popular group fitness classes, from hot Pilates and hot Barre, to slightly steamier versions of indoor cycling classes, and TRX (suspension and bodyweight exercises taken from Navy SEAL training).

Over three decades ago, Bikram Choudhury had the hot idea to practice yoga in higher temps. Now there are over 600 Bikram studios in the U.S. alone. For the 90-minute class, an instructor runs through a series of postures performed in intense heat (105 degrees) and 40 percent humidity. That’s on the low end of what a sauna feels like. Note: We don’t suggest fully disrobing in a hot class simply because it feels like a sauna.

Not all hot workouts are technically “hot.” Mimi Benz, president and founder of The Sweat Shoppe (an indoor cycling studio in North Hollywood) offers warm spin classes, where temps never rise above 82 degrees. Still too sticky? The difference, Benz says, is the safety risks of training in these temps are relatively low compared to environments above 90 degrees. In a 75-90 degree environment, as the body’s internal temperature rises, the heart beats about 10 beats per minute faster than normal. Higher than 90 degrees—the heart beats even faster.

Taking a workout to a hotter place can change the way the heart pumps. “Your heart has to work harder for blood to pump to the working muscles,” says Dr. Santiago Lorenzo, an Olympic decathlete and post-doctoral fellow at the Institute for Exercise and Environmental Medicine Blood flow distribution within skeletal muscle during exercise in the presence of chronic heart failure: effect of milrinone. Drexler, H., Faude, F., Hoing, S., et al. Medizinische Klinik III, University of Freiburg, F.R.G. The Journal of Circulation, 1987 Dec;76(6):1344-52. .

To regulate body temperature, the body sweats more in high heat, and consequently loses nutrients and minerals. “Sweating promotes detoxification and elimination through the skin, which is the body's largest eliminating organ,” Benz says Arsenic, cadmium, lead, and mercury in sweat: a systematic review. Sears, M.E., Kerr, K. J., Bray, R.I. Children’s Hospital of Eastern Ontario Research Institute, Ottawa, ON, Canada. Journal of Environmental Public Health, Epub 2012 Feb 22. . But other experts believe the main function of sweating is simply to cool down, and extra sweat may impair natural detox function by the liver and kidneys. Since we don’t often choose to be locked up in an armpit of a room, our bodies are forced to adapt. “An external load like excessive heat can definitely be dangerous to an unconditioned individual as it increases the stress to beyond a level that they’re prepared to handle,” says Greatist Expert Kelvin Gary.

In the Hot Seat—The Answer/Debate

Studies show that there may be some negatives to heating up. Elevated temps may make heat-sensitive medical conditions worse, and increase risk for heat injury, which can range from mild cramps to a life-threatening heat stroke Yoga and pilates in the management of low back pain. Sorosky, S., Stilp, S., Akuthota, V., et al. Current Reviews in Musculoskeletal Medicine. 2008 March; 1(1):39-47. . Heat exhaustion—which includes symptoms such as nausea, vomiting, headache, dizziness, weakness, and fainting—is more likely to occur as core temperature rises, says Greatist Expert Robynn Europe.

While heat may add a level of risk to exercise, it may also offer some benefits (though research is somewhat limited). In one study, elite cyclists who hit a chilled space after acclimating to a 104-degree lab, showed improvements in performance by 4-8 percent Heat acclimation improves exercise performance. Lorenzo, S., Halliwill, J.R., Sawka, M.N. et al. Department of Human Physiology, University of Oregon, Eugene, OR. The Journal of Applied Physiology, 2010, Oct; 109(4):1140-7. . The study’s head researcher, Dr. Santiago Lorenzo believes working out in high heat can be safe because of peoples’ ability to adapt to elevated temperatures Effects of endurance training and heat acclimation on psychological strain in exercising men wearing protective clothing. Aoyagi, Y., McLellan, T.M., Shephard, R.J. Graduate Department of Community Health, University of Toronto, Ontario, Canada. Ergonomics, 1998 Mar;41(3):328-57. . But, he cautions to stay hydrated (see specific recommendations below), and listen to your body. If the heat becomes unbearable, Lorenzo says to slow the pace, cool down, and stretch.

Confinement to a hot room may not be for everyone. People with high blood pressure should take caution before heading for the heat, and same goes for pregnant women (whose internal temps should not exceed 102 degrees).

A final word of caution: Since some of these studies examine only elite athletes, researchers can’t promise the same adaptation ability for recreational exercisers. With plenty of variables to consider—fitness level, hydration status, exercise intensity, and length of exposure to the heat, more studies are needed to know how effective it can be as a training method. Moral of the story: Try it out, but bring a sweatband and drink plenty of water beforehand. The key to staying hydrated: Drink frequently and early, before you have a chance to feel thirsty during exercise. The American Council on Exercise recommends consuming fluids at regular intervals throughout the day, and sipping 17-20 ounces of water at least two hours before any hot class.

As far as gear goes, wear lightweight, breathable clothing so the body can properly cool down, and hit the scale before and after a workout. A weight loss of two percent of your total body weight or greater can be a sign of dehydration (that’s three pounds for a 150-pound person). And if you tend to get dizzy in the hot stuff (baby, this evening), or dehydrated quickly, check with your doc before trying that first hot sesh.

Which hot workouts have you tried? Tell us in the comments below.

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