Know Your Sweat Rate

One of the most important components of racing and training is staying properly hydrated. In fact, being just 2% dehydrated can lead to impaired performance. Understanding the amount that you sweat and the volume of fluids need to be consumed during training and racing can lead to drastic improvements in running performance. Knowing your sweat rate is the first step towards improved performance on race day.

What is Sweat Rate?

Sweat rate refers to the amount of sweat that is lost during an hour of vigorous exercise. It is dependent on the level of fitness, weather conditions, and exercise effort. As athletes become more fit, their bodies work more efficiently, meaning that they produce more sweat.

Why is Sweat Rate Important?

Knowing your sweat rate is important for two reasons: one, to know how much water or sports drink to consume after exercise, and two, to know how much water or sports drink to consume during long races. By taking in the proper amount of fluids the effects of dehydration, such as impaired performance and muscle cramps, can be mitigated. In addition, optimal hydration primes muscles for improved post-race or post-workout recovery.

Calculating Sweat Rate

To determine sweat rate you should first weigh yourself immediately before a run wearing as few articles of clothing as possible. Next, weigh yourself immediately following your run, being sure to remove any sweat-soaked clothing. Subtract your post-run weight from your pre-run weight. Now, multiply that number by 16 in order to convert lbs to ounces. Next, correct for any gels or drinks that were consumed during the run. For instance, if you drank 8 ounces of water, add that value to the difference between your pre- and post-run value. Next, divide the total number of ounces lost by the number of minutes that you ran. Finally, multiply that value by 60 in order to know your sweat rate in units of ounces per hour.

How to Use Sweat Rate

Now that you know your sweat rate, you can use this information to fuel your long runs and races. For instance, if you find that you sweat 30 ounces per hour, you should aim to take in 20 – 25 ounces per hour during your next half or full marathon in order to maintain optimal hydration. Be sure to calculate sweat rate throughout your training, and also try to mimic race day weather conditions as closely as possible.