The Science of Sweat

The Science of Sweat

Always wondered what the science was behind sweat? Well you're not the only ones. Gymbox VPT Jayne Lo explains what gets us in a sweat.

Have you ever wondered why sometimes you push yourself so hard in the free weights room training upper body but barely break a sweat, then on leg day, you’re so sweaty you get asked if you’d just gotten out of the shower after merely a few sets of squats?

There are a few assumptions that are commonly misunderstood in society:

1) I sweat a lot therefore it was a hard workout.

2) I sweat more than you therefore I have more body fat than you.

3) I sweat a lot therefore I am unfit.

Now, to disprove these misunderstandings, we need to learn the basic science behind sweating.

Don't sweat it

When we exercise or are active, our body temperature rises. The hypothalamus in the brain notices a temperature beyond normal threshold, hence a process called negative feedback is activated, whereby a change causes the body to respond by doing what it can do reverse that change, because the body is no longer at its optimal state of function. So as body temperature increases, blood vessels dilate to release excess heat by exerting sweat. Once body temperature returns to normal, the brain deactivates these processes.

When the hypothalamus sends signals to sweat glands, sweat is produced. The body has two types of sweat glands:

1) Eccrine sweat glands – which produce most of our sweat and are stimulated when body temperature rises.

2) Apocrine sweat glands – which produce sweat due to emotional response (such as nerves, excitement, anxiety or fluctuating hormones), hence why our palms get sweaty before public speaking or performing in front of an audience.

Staying cool

So how does sweating actually cool us down? Water released from our pores evaporates, which cools our skin and removes excess heat. To convert water molecules from liquid to vapour, heat energy increases the speed of water molecules so they can be released as gas. Because these water molecules are in constant motion, the energy from the movement of water molecules (kinetic energy) also increases. The hotter water becomes a gas (heat released from body), leaving behind cooler water in liquid form (sweat). This is why although your skin remains warm when you exercise, your sweat droplets remain cool. Not all of the body’s heat energy is lost through sweat however, some is directly radiated from the skin to the air, and some is lost through respiration.

We're gonna make you sweat

We all have an average of two to four million sweat glands. But how much we sweat is determined by many factors including gender, genetics, environmental conditions, age, or fitness levels. Two of the main contributors to how much sweat is produced are an individual’s fitness level and body weight. If an individual weighs more, sweat is likely to increase because the body must exert more energy to function and there is more body mass to cool down.

Contrastingly, a fitter individual will start sweating earlier and more easily because their bodies are more efficient at regulating their body temperature. If the body is able to sweat and cool itself down earlier, it is more likely to be able to work out harder for longer, hence achieve optimum potential.

Common misunderstandings

What you need to realise is that sweating is not an accurate measure of weight loss. Yes you 'lose weight' when you sweat, but that’s because your body has released and lost water, hence you weigh less. This doesn't mean you have immediately dropped 1lb of body fat. If anything, one thing you do need to remember is that sweating can cause dehydration, which in turn leads to poorer performance during your training sessions. A reduced ability to push yourself as hard in your workout could hinder your ability to see results in the long term if you continuously dehydrate yourself during exercise. So don’t assume that as long as you sweat a lot in your session, you’ve achieved a good workout.

A common trend amongst weightlifters is that they tend to sweat more when training their lower body. Theories have found that during exercise, the body needs to pump more blood to the muscles working, which also stimulates the eccrine and apocrine glands along with increased body temperature. Now we obviously carry bigger muscles in our lower bodies, which is why lower body weight days tend to be the sweatier ones.

Sodium: the misunderstood electrolyte

"Sodium is a misunderstood electrolyte, not helped by the medical world’s focus on it being 'bad'" argues Canadian sports medicine expert, Dr. Stoddard. "To anyone sweating, it’s something needing replenishing like anything else being lost from the body.” Stoddard agrees that as part of our daily diet, it needs to be reduced to a certain extent. But when we sweat, and live an active lifestyle where sweating is part of a daily occurrence, it is an important element to be replaced and should be treated no different to any other nutrient the body needs for optimal health.

So arguably, sodium (along with potassium and chloride) is the most important electrolyte in sweat. If you come across any symptoms experienced while exercising such as headaches, cramping, energy depletion, nausea, could be linked to mineral depletion. So aside from the obvious of drinking lots of water (2 to 3 litres a day, and an extra litre on training days), put salt in your cooking, but of course, don’t over do it and eat lots of store-bought already-salted food.

What else can you do?

It is vital that when exercising, you:

A) Wear sweat-wicking clothes so heat is not trapped to your body.

B) Keep head clear of hair as that would help your body dry faster.

C) Remove any make-up prior to working out, as make-up and lotions block sweat glands, which can cause irritation and heat rash.

D) Remove excess hair from armpits to reduce body odor when sweating, as hair traps bacteria and sweat.

Along with water, we release salt and wastes like urea when sweating. While it may seem efficient to rid of these materials through sweating, it actually reduces the efficiency of evaporative cooling. Therefore it is important that you wear outfits that does not trap sweat to your skin when exercising.

E) Stay hydrated throughout the day. If you go into your workout dehydrated, you won’t be able to sweat as efficiently and hence reduces your ability to perform as your body struggles to cool itself down.

F) Finally, clean up after any sweat you may leave behind on machines.

Doing the above would not only help your body cool itself down more efficiently, but will also make you a more pleasant gym user.

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