Sweating – What is Sweat?

By Kelli Calabrese MS, CSCS, ACE

You’re puffing along on the treadmill at an even pace with the guy to the right and left. You are drenched in sweat. The guy on your right has a small stain on his shirt, and the guy on the left strides with barely a bead of sweat on his brow. No two people produce the same amount of sweat, even doing the same workload?

Some people can workout on their lunch break and go right back to their desks just as fresh as before, and others would be offensive unless they hit the shower. While you may not think of it this way, sweat is good for your body. How much we sweat is determined by a number of factors.

What is sweat? Sweating is the body’s most effective way of cooling itself. During exercise or when exposed to a hot environment, heat is released by the body and body temperature rises.

The rise in body temperature causes an increase in sweating and blood flow to the skin. As a result, heat is removed by the evaporation of sweat from the skin, radiated from the body to the cooler surroundings, and is lost by convection to moving air.

What causes sweat? The human body is approximately 55-65 percent fluid. We lose water from our body in one of four ways: perspiration, urination, respiration and leaky skin.

Respiration and leaky skin produce what is known as insensible water loss, which amounts to approximately 500 milliliters per day. However, adults need to replace anywhere from 2-10 liters of water each day, depending upon genetics, fitness level, exercise intensity, environmental conditions (temperature, humidity), clothing, hydration and age. Water lost to perspiration occurs during exercise (or sometimes in response to stress) or in hot, humid conditions.

What determines how much an individual sweats? Why some people sweat more than others is determined by the number of sweat glands they possess. Humans are born with 2–4 million sweat glands. While even newborns sweat, the number of active sweat glands increases once you reach puberty.

The most concentrated area of sweat glands is on the bottom of the feet, while the least concentrated area of sweat glands is on the back. While women have more sweat glands than men, men’s sweat glands are actually more active, and hence, they tend to sweat more.

Other than genetics, fitness level appears to play the most active role in how much individuals sweat. Exercise intensity plays a role: The harder your body works, the higher the body temperature and the greater the sweat loss. However, as individuals increase their fitness levels, they become better sweaters. Fitter individuals sweat sooner and more. In addition, the body more easily adapts to exercise in warmer temperatures by sweating more.

Some studies have shown that elite athletes can raise their metabolisms and begin sweating in the time period prior to beginning exercise. Their bodies become so efficient that they begin warming up in preparation for exercise.

Other factors that influence how much an individual sweats include the environment and clothing. Higher temperatures cause individuals to sweat more quickly and to lose more fluids through sweat. In addition, if humidity levels are high, it’s more difficult for sweat to evaporate, which affects a person’s ability to cool off. Wearing fewer and looser-fitting clothes helps promote heat loss.

The amount of water lost by the body through sweat is enormous. People typically fall into three ranges: low, average or high sweat loss. Those who fall into the low sweat-loss range lose up to a quart of sweat per hour during exercise; those in the average range lose up to two quarts per hour during exercise; and those in the high range lose up to 3 quarts.

Those who fall into the high range are at greater risk of dehydration, fatigue, cramps, heat intolerance and slow recovery after exercise.

The key to replacing water lost through sweat is to know your sweat rate. Weigh yourself naked pre- and post-exercise, and then adjust for deficits. For instance, someone weighing 152 pounds prior to exercising, and 130 pounds after exercise would need to replace 2 pounds of water weight, or 32 ounces of water (152 – 150 = 2 lb. = 32 oz.).

It’s important to note that sweat is not just made up of water. It’s also composed of ammonia, calcium, chloride, copper, creatine, iodine, iron, lactic acid, magnesium, manganese, phosphorus, potassium, sodium, urea and uric acid. Sodium and chloride are the predominate nutrients in sweat, with potassium, calcium and magnesium following, and all other nutrients accounting for trace amounts.

People lose sodium through sweat in different concentrations. Some people’s sweat contains high levels of sodium, while others have low or average levels. Those who lose high levels of sweat sodium are at high risk of muscle cramps. Exercisers who cramp up usually display obvious signs: profuse sweating, being prone to dehydration or having legs and arms caked in salt after exercise. A drink high in sodium and potassium is recommended for these individuals during post-exercise.

Sweat is cool

If you are dripping in sweat after exercise, consider that your reward. The fact that you are sweating profusely could be the result of exercise success.

The following recommendations are given as the best ways to replace sweat:

  • Consume 20 ounces of water in the 60 minutes prior to exercise.
  • Drink 1 cup of fluid every 15 minutes during exercise.
  • Drink 16 ounces per pound of lost body weight after exercise.
  • In general, drink at least 20 ounces of fluid at all meals.
  • Limit caffeine and alcohol intake.


About our Expert:

Kelli Calabrese, MS, CSCS  is a 19 year fitness industry leader, author, trainer, international presenter and body transformation specialist. Kelli is on the Board of Directors for the American Association of Personal Trainers, An Expert Fellow for the National Board of Fitness Examiners, the Lead Exercise Physiologist for NESTA (National Exercise Sports Trainers Association), Publisher of Personal Fitness Professional Magazine and has attained over 20 fitness and nutrition certifications. Kelli is the co-author of Feminine, Firm and Fit and is available for fitness consulting. She can be reached at Kelli@KelliCalabrese.com.

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