There are times (think: indoor Spin classes, indoor training sessions, or really hot really long rides) where we just pour sweat. We can ride every day and feel fairly fit, yet in certain circumstances, we’re drenched.
People have been correlating sweat and calorie burn for decades, but can you actually tell how good of a workout you got based on sweat alone?
We spoke to Bryan Saltzman, M.D., a Charlotte, North Carolina-based sports medicine physician, and Natasha Trentacosta, M.D., a Los Angeles-based sports medicine specialist, to find out if sweating actually burns calories, why some people seem to perspire way more than others, and what your sweat stains (or lack thereof) say about your workout.
Sweating a lot during exercise automatically means you got a good workout in (i.e. burned a lot of fat and/or calories). Sweat is basically a universal sign for exertion, so it’s easy to assume that more of it equals a more intense workout.
Here’s a real quick recap of sweat’s actual purpose: Those little droplets are your body’s way of regulating your body temperature when things heat up, which happens when you put your muscles to work during exercise.
“Our sweat glands produce a water-rich secretion onto our skin’s surface,” says Saltzman. When the sweat evaporates off your skin, the result is a natural cooling effect, which in turn helps to keep your core temperature from getting too high, he explains.
It’s true, though, that some people seem to be a lot sweatier than others. “Not all people sweat the same doing the same activity,” says Trentacosta. Yes, your fitness level plays a role—the better shape you’re in, the more efficient your body becomes at regulating temperature, says Saltzman. But there are other factors at play. Men generally perspire more than women, and heavier people tend to sweat more than those who weigh less.
Still, it’s possible for two people of the same sex, size, and fitness level to sweat differently. Genetics play a part in sweating, so the sweatier person might have more sweat glands than their drier counterpart.
“Furthermore, the physiologic response of individuals’ thermoregulatory autonomic nervous systems are just inherently different and react differently to temperature and exercise,” Saltzman says. In other words, the way your body handles changes in temp might just be different from someone else’s.
External factors play an important role, too. The weather conditions such as heat and humidity often make the biggest impact on your sweat rate. Consuming alcohol or caffeine before a workout can make you sweat more, Trentacosta notes. Then there are your clothes: Heavier garments or those made from synthetic materials (like polyester) trap more heat and result in more perspiration than…