November 4


How to Calculate Your Sweat Rate | Water & Hydration

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Knowing how to calculate your sweat rate means you can be much more specific with your own training nutrition.

Almost 75% of the body is water, keeping it topped up is crucial.


You've probably heard that for everyday health you should drink 2 litres of water daily.

While this is a good starting point, it doesn’t take into account our individuality. Likewise, it certainly doesn’t account for our requirements while training and exercising.

With my coaching clients, I always provide tailored hydration prescriptions with their custom meal plan.

Hydration tip

Take a litre bottle of water with you to work, uni or college. Keep it on you desk and be sure to sip from it throughout your day. This way you'll always be topping up. Get into the habit of regular drink breaks to keep your fluid levels on point.

Getting more precise about workout hydration and rehydration

When it comes to timing working out, you need to consume more water than you lose.

This is the only way to maintain and even improve your hydration levels.

Don't think that this only applies in hot weather. You still sweat in when it’s cold, although not as much.

Generally, it's recommended that for training days you drink 1 litre of water for every 1000 calories expended.

Although a good starting point, this doesn’t account for your prior levels of hydration or post-workout needs. Nor does it take into account your personal sweat rate.

Different people produce different volumes of sweat during the same workout. Therefore, it's impossible to know how much you need to rehydrate if you don't know your sweat rate.

How to calculate your personal sweat rate - a more precise way to measure your hydration needs

If you weigh yourself pre and post-workout, you'll get a good idea of how much fluid you lose through sweating.

In doing so, you'll calculate your personal sweat rate. Consequently, you'll be able to implement the necessary combative hydration strategy.

To calculate your sweat rate:

Record the temperature. Weather conditions play a big part in how much we sweat. It'll be handy for subseuqent sessions to adjust your hydration strategies depending on the conditions.

Weigh yourself before your workout in minimal clothing - wearing just underwear if appropriate.

Take a note of the clothing you will be wearing and its 'breathability'.

Note the duration and intensity of your workout. If you have a heart rate monitor, record the data. Otherwise, just general comments are fine.

Weigh yourself after the workout, again in minimal clothing. Sweat-soaked clothing will obviously skew the accuracy of your measurements, so remove as much as possible. You might not want to do this in a busy gym.

Calculate how much fluid you have lost by subtracting your pre-workout weight from your post-workout weight. Convert this figure into litres (1kg = 1 litre)

Work out your sweat rate by dividing the volume of sweat produced by the duration of your workout. You're looking for a figure in litres per hour.

You should then aim to drink this amount, plus a bit more, during similar workouts

Once you have determined your sweat rate you will be able to hydrate according to your rate of dehydration.

Doing this will enable you to exercise optimally.

I'll write another article on the types of sports drinks available. But in general, water will be sufficient for workouts lasting up to an hour.

If you'd like to know more about hydrating for performance and how sports drinks might help, drop me a comment below.

About the author

Paul Stokes

Paul Stokes BSc (Hons) is a Certified Personal Trainer, Accredited Sports Nutritionist, qualified Exercise to Music Instructor, Precision Nutrition coach, Massage Therapist and teaches 8 of the Les Mills Group Exercise programs.

He currently works in the Oil & Gas industry as a Wellness Coach, imparting his vast knowledge and experience to improve the quality of life of several hundred offshore workers.

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