Formidable fuelling
How to gauge your electrolyte intake and train your gut for big summer rides
Session 01 Calculate your sweat rate
Expert Chris Harris, Precision Hydration sports scientist
Why do it? Estimating sweat rate can be useful when working out how much and what type of fluid (water or electrolytes) you need to drink in training and in races
Kit needed An accurate set of weighing scales and a dry towel
Before the workout Go to the toilet, then weigh yourself (ideally in the nude) - remember if you are planning to drink, hold your bottles and include them in your “before” weight.
During the workout Usually people try to simulate ‘race pace’, so they can calculate how much fluid they need for races. Be sure to log the temperature, humidity and intensity of the workout, so you can log how your sweat rate changes across different conditions. Indoor sessions are much easier to control, so we’d recommend doing this kind of test on the turbo or on a treadmill.
After the workout Towel yourself as dry as you can, then weigh yourself (again, ideally in the nude as your clothing can retain a lot of sweat). This is your “after” weight. Remember to hold your water bottles (even if they’re empty) to account for how much you drank.
Estimating sweat rate Simply subtract “after” weight “before” weight. For example: following a 1hr workout, if “before” weight was 71kg, and “after” weight was 70kg, this equals a 1kg loss. 1kg is equal to 1L, therefore for this workout, your sweat rate would be 1L per hour. This will give you a guide to how much fluid you should aim to replace during exercise. Replacing 100% of your fluid losses isn’t necessary, and can actually be detrimental to performance, but under hydrating can be just as detrimental, so it’s important to strike the correct balance.