Sweating and running For Winners

Every runner sweats, but the rate varies widely. Knowing your personal sweat rate helps you hydrate correctly and avoid both dehydration and overhydration.

Sweat rate is simple to measure. Weigh yourself (without clothes) right before a run. Run for one hour at a typical training effort, noting exactly how much fluid you drink. After the run, towel off and weigh yourself again. Each kilogram lost equals about one liter of fluid lost. Add back the amount you drank to calculate your total sweat rate per hour. Example: if you lost 0.8 kg and drank 0.5 liters, your sweat rate is 1.3 liters per hour.

Sweat rate depends on temperature, humidity, clothing, and intensity. Repeat the test in different conditions to learn your range. Some athletes lose less than 0.5 liters per hour, while others exceed 2 liters. Both ends of the spectrum are normal.

Hydration strategy should match your sweat rate. In shorter runs (under an hour), water is usually unnecessary unless conditions are extreme. For longer sessions, aim to replace 60–70% of your fluid loss. Trying to drink as much as you sweat can lead to stomach distress and, in rare cases, hyponatremia (low blood sodium). A practical target is 400–800 ml of fluid per hour, adjusted to your personal test results.

Electrolytes matter too. Sweat contains sodium, so in long runs or hot weather, add a sports drink or electrolyte tablets to prevent cramps and maintain performance.

By tracking your sweat rate and practicing hydration in training, you’ll know exactly how much to drink during races. That knowledge can be the difference between fading late and finishing strong.

Do you want me to also draft a step-by-step field guide (like a checklist runners can follow during training), or keep it in article format?