Sweat rate

Sweat rate refers to the volume of sweat produced per unit of time, usually measured in litres per hour. It indicates how quickly the body loses water through sweating during activity or heat exposure.

Factors affecting sweat rate

Typical sweat rates during exercise range from about 0.5 to 2 litres per hour, though some individuals may lose more than 3 litres per hour under extreme heat or high‑intensity conditions. Sweat rate is influenced by ambient temperature, humidity, exercise intensity, clothing and protective gear, aerobic fitness, body size, genetics and heat acclimation. Hot, humid weather and vigorous activity increase sweat losses, whereas cool or low‑intensity conditions lead to lower rates. Heat acclimation training can raise sweat rate while lowering the sodium concentration in sweat, improving cooling efficiency. Initial hydration status and body mass also play roles, with larger athletes often sweating more than smaller individuals.

Measuring and applying sweat rate

To estimate personal sweat rate, athletes can weigh themselves before and after exercise, accounting for any fluids consumed and urine produced. A loss of 1 kg indicates roughly 1 litre of sweat. Tracking this over several sessions helps determine an average. For example, a runner who loses 0.8 kg during a one‑hour training session and drinks 0.3 litres has a sweat rate of about 1.1 litres per hour. By knowing this value, athletes can plan fluid intake during and after exercise to prevent dehydration while avoiding overdrinking.

Sweat rate is an individual characteristic that varies widely with conditions. Understanding how much sweat you lose enables you to develop a hydration strategy that maintains performance and reduces the risk of hypohydration.

Related Terms: Hydration, Prehydration, Rehydration, Sweat sodium concentration, Hypohydration