Sweating: good for you and good for your performance

pre-Christmas 2015 run in the dreary dead of winter
(note trees) -- except it was 71 deg F/ 22 deg C!

I was not expecting to go running on Christmas Eve 2015 in shorts and a tank top and return as sweaty as if it were a warm summer's day.

But it was nearly that, at 71 degrees F (22 degrees C), record-breaking for Washington, DC (average December 24th temperature is 30 degrees cooler!). Crazy.

Not only that, my little GPS watch showed that my pace was far faster than I'd expected (5:20/km or 8:35/mi in what was supposed to be an easy run), supporting the idea that sweating helps improve athletic performance, on top of keeping you cool in hot weather.

Historically not a major concern in winter, sweating is generally good for us as we exercise.

Sweating is our body's means of staying cool. Eccrine sweat glands, found all over our body, produce clear, odorless fluid that is basically water + salts. As the water evaporates off our skin, we feel cooler (and saltier).



We humans can sweat up to 2-4 liters (quarts) per hour, or 10-14 liters per day. On a hot day, or when our muscles heat up during a workout, we produce more sweat to maintain a healthy and effective body temperature of between 98 and 103 degrees F (36.7 - 39.4 degrees C).

Sweat evaporates and cools our body more efficiently when the air is dry -- if we are in uber-humid Bangkok and the air is already nearly saturated with water vapor, sweat won't evaporate and we don't cool down nearly as much. When exercising in hot, humid weather, we must generally temper our expectations and work on effort, rather than speed.

Rafael Nadal showing how fit he is, staying cool in the heat of the match.

Yet who sweats the most (in general)?  People that are overweight and people that are very fit. The first group must move a large amount of weight inside thicker insulation, and the second are primed and practiced to begin the cooling process quickly, so they start sweating earlier and easier. That would definitely be me.

The darker side of sweating

That odoriferous sweat you smell when you are stressed or nervous comes from the apocrine sweat glands, found in the armpits, but also in small areas at your eyelids, ear, breasts, and genitals. Yes, they also start working when you are sexually excited. They must be pretty special!

The more oily fluid they produce doesn't smell until bacteria find and start to degrade it. Fun fact: the oily (soon-to-be smelly) secretions are used by other mammals to mark territories, attract a mate, and warn off potential competitors or predators - these are the glands that skunks use to spray your dog.

Lady in "Airplane": Nervous?   Ted Striker: Yes.
Lady: First time?   Ted Striker: No, I've been nervous lots of times.

Animals with few sweat glands, such as dogs, accomplish similar temperature regulation results by panting, which evaporates water from the moist lining of their mouth and throat.

I like the concept of this -- just make sure you're hydrated!

Some animals, like the koala and some primates, press their skin against trees when branches are cooler than surrounding air. Others, such as the elephant, avoid overheating by dissipating body heat through their large, thin ears.

Sweating, then, is a Big Deal, as it allows people (and some other animals) to stay cooler while still functioning (i.e. hunting), one of our species' few competitive advantages in our prehistory years.

The heat still slows us down, so sweating performs the same thermoregulation function for athletes today, though anyone sweating heavily will have to replenish fluids before long!