Ew! Why Do I Sweat So Much When I Work Out?

Bodybuilder wipes the sweat at fitness gym
How much you sweat when you exercise depends on a variety of factors. (Image: Adobe Stock/Drobot Dean)

There’s nothing quite like an hour-long indoor cycling class to get your legs pumping, your heart thumping and your sweat dripping — all over the floor. If you feel like you’re sweating buckets during exercise, you’re not alone.

We all sweat when we work out; that’s how the body works. But it’s the amount of sweat you produce during physical activity that sets you apart from the person on the bike next to you — even if they’re completing the same workout.

It turns out, sweat is kind of complicated. That’s why we asked the experts to give us a simple lesson about why every body sweats differently.

The Physiology of Sweat

In case you were curious (you’re reading this, so we know you’re at least a little curious), your body has two to four million sweat glands. Yep, millions.

There are two major types of sweat glands in your body — eccrine and apocrine. The eccrine glands, which cover most of your body, including your forehead, cheeks, palms and soles of your feet, are responsible for thermoregulation (how you regulate your body temperature), says Matt Bayes, M.D., sports medicine and regenerative orthopedic specialist at Bluetail Medical Group. Your apocrine glands are in regions with lots of hair follicles like the armpits and groin).

When your body temperature rises (like when you exercise), your brain reacts by releasing sweat from the eccrine glands, says Brian Schulz, M.D., orthopedic surgeon and sports medicine specialist at Cedars-Sinai Kerlan-Jobe Institute. Then the sweat, which is composed primarily of water and sodium chloride (salt) evaporates from your skin, removing excess heat and cooling the body.

What’s interesting, though, is that the exact mechanism of sweating isn’t completely understood. “We do know that a region of the brain called the hypothalamus is the body’s primary thermostat,” says Vincent Meoli, M.D., regional medical director at American Family Care. Nerve fibers travel from the hypothalamus through the spinal cord and innervate these tiny sweat glands and that the hypothalamus, in combination with skin temperatures, regulates sweating.

Portrait of young female runner
The harder you work out, the more you sweat. (Image: Uwe Krejci/The Image Bank/GettyImages)

Why Every Body Sweats Differently

The amount of sweat you produce depends on several factors, including your genetics and any underlying health conditions, your gender, the intensity of the exercise and the environment.

1. Your Fitness Level

You might be embarrassed by the amount of sweat dripping from your body after an intense workout, but what you may not realize is the more your body adapts to physical activity, the more you sweat (and this is a good thing).

When you exercise regularly, your sweat physiology actually changes, says Rob Raponi, a naturopathic physician. In other words, the more often you exercise, the more you sweat.

“This is a smart and necessary adaptation because your body begins to cool you sooner into your workout and more efficiently since it has been primed to know that you’re going to keep working out and need to stay cool,” he says.

2. Your Genetics

In addition to adaptation, your body also sweats differently because of genetics. Sometimes we’re just dealt a hand we have little influence over, says Raponi. “Some of us just sweat more and easier than others, while some seem to not sweat at all,” he says.

Whether this is an evolutionary trait developed over time or some sort of lucky (or unlucky) mixing of genes, Raponi says we really have no control over some things, and sweating is one of them.

3. The Environment

It’s no secret that hotter temperatures increase how much you sweat. That’s because your body needs a way to cool down when working out in the heat. But, Raponi says, another factor that often gets overlooked is humidity.

“On a humid day when moisture in the air is high, evaporation takes place at a much slower pace,” he says. “The air is saturated with water already and simply does not want to absorb anymore; this includes the sweat off your body.”

Because a vast majority of the cooling that occurs with sweating relies on evaporation taking place, the body must work harder to release more sweat in an attempt to bring as much heat away from its core as possible, Raponi says. That’s why you need to be extra careful when working out in the heat and humidity.

4. A Medical Condition

If you sweat too much without any other apparent cause, you could be dealing with hyperhidrosis, a condition that causes sweating in excess of what you need for thermoregulation. Dr. Meoli says it’s most commonly idiopathic (with no other underlying cause) and not considered dangerous.

However, it can cause significant social stress for people who suffer from it. Dr. Meoli says there are a variety of treatments ranging from topical antiperspirants to Botox injections to the use of microwave thermolysis (the use of microwave energy to destroy the glands). See your physician if you want more information about this condition or treatment options.

Man with water bottle at gym
Drink lots of water before, during and after your sweat sessions. (Image: Ridofranz/iStock/GettyImages)

How to Stay Hydrated

Regardless of how much you sweat, it’s important to drink plenty of fluids to replace any liquid lost through sweating. Before a workout, drink eight to 12 fluid ounces of water. Then consume another three to eight fluid ounces of water every 15 to 20 minutes during workouts shorter than 60 minutes long.

If you sweat heavily and your sweat tastes pretty salty (or you notice a lot of white residue on your clothes when your sweat dries), you may also need to ingest some salt in your post-workout snack or smoothie to make up for electrolyte losses.

Don’t go overboard with sports drinks, though, as they often contain a lot of unnecessary sugar and calories. They’re really only recommended for athletes who train longer than 60 minutes.

Sometimes it can be helpful to weigh yourself before and after a heavy or long exercise session. You should avoid losing any more than 2 percent of your pre-exercise weight to prevent dehydration.

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