Hydration during Workouts

Nutrition goals during your workout should be to replace the fluid lost through sweat and make sure you have enough fuel (carbohydrate) to last the distance and work at your hardest.

When Do I Need Fuel?

Whether you require carbohydrate or not during exercise depends on the length and intensity of exercise. Generally, if your workout involves less than an hour of activity, you will not need to top up fuel levels. If your workout last longer than an hour, or if you were unable to consume carbohydrate leading up to the workout, you may benefit from consuming carbohydrate during the workout session. A sports drink or sports gel is the easiest way to consume carbohydrate during exercise.

The Hydration Zone

When it comes to hydrating during exercise, the goal is to avoid gaining weight (a sign that you have consumed too much fluid) and avoid losing more than 2% of your pre-exercise body weight (the level of fluid loss beyond which athletic performance is undermined). This is the hydration zone, where individuals perform at their best and avoid the adverse health effects of dehydration and over-hydration.

What is a Sweat Rate?

It is essential to understand that the way to stay in the hydration zone is to consume fluids at a rate that keeps pace with your sweat rate. While this generally requires about 400-600 millilitres every hour of exercise (preferably in smaller amounts taken frequently), fluid needs vary based on factors such as body size, exercise intensity, and workout conditions. That means that everyone will have their individual sweat rate, so it is best that you calculate your sweat rates for the various conditions in which you train.

Basic Sweat Rate Testing

You can quickly estimate your fluid requirements by weighing yourself before and after exercise sessions. Each kilogram (kg) of weight loss is equivalent to approximately one litre (L) of fluid.

  • Weight yourself before training – initial weight.
  • Weigh yourself after training – final weight.
  • Subtract final weight from initial weight.
  • The difference plus the volume of fluid consumed during training equals to your sweat rate for that period.
  • Divide this by the total time (hours, hr) to determine hourly sweat rate.

Sweat Rate (L/hr) = [Initial Weight (kg) – Final Weight (kg)] + Fluid (L)/Time (hrs)

What Should I Drink During Exercise?

Water is cheap and effective for hydration in low intensity or short duration workouts (i.e. less than one hour). A sports drink may be more effective for longer sessions and where sweat loss is high, for example when training in hot or humid conditions, although you can still hydrate with water. Sports drinks provide carbohydrates to top up fuel levels during exercise, and the taste may encourage people to drink more. Sports drinks also contain electrolytes such as sodium and potassium which help you retain more fluid and replace the electrolytes lost in sweat. The sodium also helps maintain the drive to continue drinking fluid when exercising, which is crucial to meeting fluid needs.

The above content is intended for informational and educational purposes only, and in no way is any of the content to be construed as medical or dietary advice or instruction. For personalised medical or diet advice, please consult with your medical/health or dietary/nutritional professional.


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