Fluid intake is often overlooked as a nutrition strategy for optimum performance. Yet your physical endurance, co-ordination and concentration can depend on it. It is very important, therefore to maintain a positive fluid balance whilst exercising. Thirst is a sign that you may be dehydrated, so you need to plan to drink before you feel thirsty. Fluids like sports drinks can also provide carbohydrate as an energy source for working muscles and electrolytes (e.g. sodium that is lost in sweat).
The athlete's fluid needs
Everyday, we should drink about 2 litres of fluid to make up for water lost from the body, (i.e. to restore water balance in the body). This volume, however, does not include losses linked to perspiration during exercise. Sweating allows our bodies to lose the heat generated by physical exertion. Sweating rates increase as the work becomes harder or the environment becomes hotter. Even mild dehydration will negatively affect your performance, so get into the habit of drinking regularly.
You can easily estimate your fluid requirements by weighing yourself before and after activity. Each kilogram of weight loss is equal to about 1 litre of lost fluid. Aim to replace 1 ½ times your weight loss at the end of your exercise session. It’s important to plan ahead for fluid replacement. Where possible, begin drinking early during exercise. Depending on the type and intensity of exercise you are doing, you can train yourself to drink about 150-350mL of fluid every 15-20 minutes.
What to drink
Thirst for success!
No matter what your sport – running, cycling, swimming, tennis, walking or golf – fluids are essential. Follow these tips to stay well hydrated during exercise:
- Start your exercise session well hydrated and be aware of your increased fluid needs in hot weather. Drink 400 – 600mL about 2 hours before exercise to top up fluid levels
- Take advantage of all breaks during your sport. Make drinks available for all these occasions and try to keep them cool (10-15°C) (e.g. pre-freeze drinks so that they will still be cool once they have melted)
- Choose fluids that will help you meet all your nutrition goals. A sports drink provides extra carbohydrate (4-8% as glucose or a glucose-fructose mixture) for energy and added sodium (salt) to stimulate your thirst and help replace what’s lost in sweat (important for prolonged endurance events like Ironman triathlon). Both carbohydrate and sodium enhance the taste of sports drinks and therefore encourage you to drink more
- Don’t rely on visible sweat as a guide to your fluid needs. Some athletes can’t see their sweat losses (e.g. swimmers who are already wet, or cyclists whose skin is quickly dried as they speed through the air)
- Aim to drink early in your exercise session and then at regular intervals. Most people can learn to drink about 600 – 1000mL per hour. For example, try drinking 150-350mL every 15-20 minutes
- After exercise, rehydrate quickly as part of your immediate recovery plan. Weigh yourself to help determine how much fluid you have lost. Over the next couple of hours, plan to drink 50% more fluid than you lost (e.g. 1.5 litres if you lost 1kg). Choose a recovery plan based first on fluids and high carbohydrate foods. Drinking a sports drink containing sodium can help with replacing fluid losses
Sport and alcohol
Alcohol is not good for fluid replacement – in fact, it acts as a diuretic and may contribute to dehydration by increasing urine losses. Alcohol is not advisable just prior to or during exercise. After exercise, alcohol intake can compromise your recovery by promoting dehydration. If you are injured during exercise, alcohol can increase swelling and impair muscle tissue repair.