Start workouts well hydrated
Starting workouts fully hydrated will help you train harder and achieve more during workouts. Fluid deficits as low as 2 per cent (i.e. a deficit of 1.2 litres for a 60 kilogram person) can have negative effects on performance.
Dehydration makes exercise much harder and puts your health at risk, so it is important not to carry fluid deficits from the one exercise session to the next. Consuming 400-600 millimetres of water or sports drink at least 2-4 hours before your workout will help make up any fluid deficits from previous workouts.
The hydration zone
When it comes to hydrating during exercise, the goal is to avoid gaining weight (a sign that you’ve consumed too much fluid) and avoid losing more than 2 percent of your pre-exercise body weight (the 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 400-800 millimetres 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.
1. Weigh yourself before training – Initial Weight
2. Weigh yourself after training – Final Weight
3. Subtract Final Weight from Initial Weight
4. The difference plus the volume of fluid consumed during training equals your sweat rate for that period.
5. Divide this by the total time (hours) to determine hourly sweat rate.
What should I drink during exercise?
Water is cheap and effective for hydration in low intensity or short duration workouts (less than 1 hour). A sports drink is ideal for longer sessions and where sweat loss is high, for example when training in hot or humid conditions.
Sports drinks provide carbohydrates to top up fuel levels during exercise, and the taste encourages 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 fluids when exercising, which is crucial to meeting fluid needs.
Rehydrating after workouts
After training, replacing water plus electrolyte losses is important for optimal recovery. You continue to lose fluid through sweat and urine even after finishing your sessions, so you should aim to replace losses by 150 per cent. In practice, this means that if you are 1 kilogram lighter after your workout, you need to drink 1.5 litres over the next 2-6 hours. Remember 1 kilogram weight loss equals 1 litre of fluid deficit.
If sweat rates were high, include a source of sodium to replace lost electrolytes and help the body to rehydrate more effectively. Sports drinks, milk, soup and pretzels are all examples of sodium sources that can help with rehydration after workouts. Remember that these also provide additional energy (kilojoules) and should be considered in your total energy budget.
National Guide to Fitness & Health 2019/20. (2019). Retrieved from Pro-Visual Publishing: www.provisual.com.au