Sweating – What is Sweat?

You’re running at a steady pace on the treadmill. Same speed, same effort as the person next to you. But while you’re dripping, they barely have a damp patch on their shirt. Why?

Sweating is personal. How much you sweat depends on your body, your environment, and your fitness level. Here’s what’s really happening when your skin starts to shine.

What Is Sweat?

Sweat is mostly water, with a small amount of salts and other compounds. It’s how your body cools itself down. When your temperature rises—because of heat, exercise, or even stress—your nervous system signals your sweat glands. As the sweat evaporates from your skin, it carries heat away and helps regulate your temperature.

Why Do We Sweat?

We lose water from our bodies in a few main ways:

• Urination
• Breathing
• Evaporation from the skin
• Sweating

On a regular day, we lose some water just through breathing and skin evaporation. But during exercise or in hot weather, sweating becomes the body’s main way to cool off.

Why Some People Sweat More Than Others

Sweating varies from person to person for a few key reasons:

Sweat glands: We’re born with around 2 to 4 million sweat glands. Women tend to have more than men, but men’s glands are usually more active.

Fitness level: Fitter people tend to sweat more efficiently. They often start sweating sooner during exercise because their bodies are used to regulating temperature quickly.

Exercise intensity: The harder you work, the more your body needs to cool itself.

Weather and humidity: Hot, humid environments trigger more sweat. When it’s humid, sweat doesn’t evaporate as easily, so your body works harder to cool down.

Clothing: Tight or heavy clothing traps heat, making it harder to release. Light, breathable clothing allows for better cooling.

Genetics, age, hydration, and body size also influence how much you sweat.

Elite athletes may even start sweating before their workout begins. Their bodies are so well conditioned that they prepare early for the effort ahead.

Where Are Sweat Glands Most Concentrated?

Sweat glands are found all over your body, but some areas have more than others.

• Most concentrated: palms, soles of the feet, forehead
• Least concentrated: back and lower legs

How Much Sweat Is Normal?

During moderate to intense exercise, most people lose between 0.5 to 2 litres of sweat per hour. Some people may lose up to 3 litres, especially in hot conditions.

This range is normal. What matters most is how well your body adapts and whether you’re staying hydrated.

What’s In Sweat?

Sweat is made up mostly of water, but it also contains:

• Electrolytes like sodium, chloride, potassium, calcium, and magnesium
• Small amounts of waste products like urea and ammonia

Some people naturally lose more sodium in their sweat. If you often finish workouts with salt streaks on your skin or struggle with cramps, you may be losing more than average. A sports drink with electrolytes may help.

How to Measure Your Sweat Loss

To figure out your personal sweat rate, weigh yourself before and after exercise (wearing minimal or dry clothes). For every kilogram of weight lost, you’ve lost about one litre of fluid. Just remember to factor in anything you drank during your session.

How to Rehydrate Effectively

• Drink 500–600 ml (about 20 oz) of water in the hour before exercise
• Sip 150–250 ml (about 1 cup) every 15–20 minutes while working out
• After exercise, replace 1.5 litres of fluid for every kilogram of weight lost
• Drink water regularly throughout the day, especially with meals
• Limit caffeine and alcohol, which can increase fluid loss

Sweating Is a Good Sign

If you’re dripping after a workout, that’s not a problem—it’s a sign your body is doing its job. Sweating is how we stay cool, and it means your internal cooling system is switched on and working well.

Instead of comparing your sweat levels to someone else’s, pay attention to how you feel. Stay hydrated, listen to your body, and take sweat as a sign that your system is active and responsive.