Water Loss During Exercise

Runner in the park

How much water you lose during exercise depends on a few factors, including the conditions in which you’re running, genetics and what shape you’re in. It’s not necessarily an indication of your fitness level, however, because the amount of sweating you experience during exercise can vary greatly from others. As you get into better shape, however, your body becomes more effective at handling the stress put on it and typically the amount of water loss is decreased.


It’s common to lose a significant amount of water during exercise. As you exercise, the breakdown of fuel to create energy for your tissues causes your core temperature to rise. Your body responds to this elevation by working to release heat, which it does through water, eventually releasing out your sweat glands so that it can be evaporated off your skin and cool your body.


Adequate hydration is necessary for maximal athletic and physical activity performance, but it’s also important in keeping your core temperature at a safe level. Dehydration makes your body susceptible to heat-induced conditions, which can lead to fatigue, disorientation, confusion, seizures and even death.


The hotter the temperature when you’re exercising, the more you’re likely to sweat, as your core temperature will heat up more quickly and to a higher degree. The humidity will even more significantly affect your sweating levels, because more fluid in the air makes it more difficult for your sweat to evaporate and allow your body to cool. Your body will continue to release fluid through your sweat glands without much of it evaporating.

Your Fitness Level

As you personally increase your fitness level, it’s likely to experience even more significant sweating. With consistent exercise, your body adapts and is better equipped to handle the stress of exercise, so it’s typical that you will sweat more and sooner into the workout session than you would when you weren’t in shape.

Hydrating Before and During Exercise

Hydrate before, during and after your exercise sessions. Dr. Victor A. Convertino of the American College of Sports Medicine recommends that you drink about 17 oz. of fluid two hours before you exercise so you will be hydrated and your body has enough time to excrete any extra before your session. During exercise, drink early and at regular intervals, taking small sips and consuming as much as you comfortably can.

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