You sweat during exercise to cool your body, and fitter people often sweat earlier and more.
Why
Sweat evaporates and cools you. Muscles produce heat, so your body sweats to keep temperature near 98.6°F.
What affects it
- Fitness: fitter people start sweating earlier and sweat more efficiently.
- Weight, genes and age.
- Heat and humidity.
- Exercise intensity.
How much
Sweat rates range from 0.5 to 2 liters per hour.
Tips
Drink water before, during and after. Replace salt in long sessions.
See a doctor
If sweating is excessive at rest (hyperhidrosis).
Thermoregulation
Sweating cools the body as sweat evaporates. During exercise, muscles produce about 20 times more heat than at rest. The body has between 2 million and 5 million sweat glands.
Typical rates
Sweat rates range from 0.5 to 2 liters per hour in endurance exercise, depending on heat, humidity, intensity and fitness. A study by Gatorade Sports Science Institute describes rates as high as 2.5 liters per hour in elite athletes in heat.
Fitness effect
Fitter people often sweat earlier and more because their bodies cool more efficiently. Trained athletes start sweating at a lower core temperature.
Individual factors
- Genetics.
- Body size and composition: larger people produce more heat.
- Age and sex: men on average sweat more than women.
- Environment: heat and humidity.
- Clothing.
- Acclimatization: after 1 to 2 weeks in the heat, sweat becomes more dilute and starts earlier.
Hydration
Replace fluids lost: a rule of thumb is to drink about 16 to 24 ounces for each pound lost. The American College of Sports Medicine advises drinking enough to limit weight loss to less than 2% of body weight.
Electrolytes
Sweat contains sodium, potassium and chloride. For workouts longer than 60 to 90 minutes, drinks with sodium can help.
Excess sweating
Hyperhidrosis affects about 3% of people and causes heavy sweating beyond what is needed. Night sweats, sudden changes or sweating with chest pain, shortness of breath or dizziness need medical attention.
Tips
- Wear moisture wicking clothes.
- Use a fan or exercise in cooler hours.
- Drink water before, during and after.
- Antiperspirant for underarms.
How much sweat is normal
Sweat rates during exercise commonly range from 0.5 to 2 liters per hour, depending on intensity, temperature, humidity, body size and fitness. Fitter people often begin sweating earlier and more at a given workload because their bodies are better at cooling. Sweat contains water and electrolytes, with average sodium of about 900 mg per liter but a range from 200 to over 2,000 mg per liter. Heavy sweaters and long events may need sodium replacement. Overly salty sweat leaves white marks on clothing.
Hydration and unusual sweating
The American College of Sports Medicine advises drinking fluids before, during and after exercise, for instance about 17 to 20 ounces about two hours before activity and enough during to avoid losing more than about 2 percent of body weight. Weigh yourself before and after to estimate losses. Hyperhidrosis, excessive sweating beyond what is needed to cool, affects about 3 to 5 percent of people, and treatments include prescription antiperspirants, iontophoresis, medicines and botulinum toxin injections. See a doctor for sweating at rest, night sweats with fever or weight loss, or sudden changes.
Based on data from the American College of Sports Medicine and the International Hyperhidrosis Society
