Hydration needs are highly individualised due to variations in sweat rates between people, and even for the same person exercising in different conditions. Sweat rate is influenced by a number of factors including:
- Body size – larger body sizes tend to sweat more
- Fitness level – fitter athletes generally start to sweat earlier
- Genetics – some people naturally sweat more than others
- Temperature – hot and humid conditions increase sweat rates
- Wind – air flow over the skin improves body cooling and reduces sweat rates
- Exercise intensity – as intensity increases, so does sweat rate
Dehydration and Performance
During exercise, fluid is critical for maintaining blood volume, regulating body temperature, and for muscle contraction. Sweating is the body’s way of maintaining core temperature while exercising. Generally, the body has a good capacity to tolerate low to moderate levels of dehydration; however, as levels of dehydration rise, performance can be impaired through:
- Increased heart rate
- Increased perception of effort
- Increased fatigue
- Impaired cognitive performance (e.g. skill and coordination)
- Gastrointestinal issues, such as nausea
WHAT SHOULD I DRINK DURING EXERCISE?
With so many drink options now available, deciding which fluid best suits your needs can be tricky. When choosing the best drink for you it’s a good idea to consider:
- The duration and intensity of your session
- Whether there is a need to replace carbohydrate and electrolytes during the session
- Individual preferences (e.g. flavour preferences, gastrointestinal comfort)
Check out our resource sheet on What To Drink During Exercise with some suggestions including plain water, sports drinks, and electrolytes.
WHEN SHOULD I DRINK DURING EXERCISE?
The optimal amount and timing of drinks will depend on your individual sweat rate and exercise conditions (e.g. hot vs. cold weather, easy run vs. racing, etc.). A Sports Dietitian can work with you to develop an individual hydration plan but as a general strategy:
- Begin exercise well hydrated
- Follow a hydration plan based on your individual needs while exercising
- Rehydrate after you finish exercising as you are unlikely (and it’s not necessary) to replace 100% of fluid losses during exercise
Modified from Sports Dietitians Australia, 2016 Factsheet: Hydration: How Much Should You Drink During Exercise?