Dehydration degrades aerobic performance
Aerobic performance can be negatively affected by a fluid deficiency, especially in a warm environment when fluid loss is higher than 2% of body mass2 3. Drinking regularly during exercise can prevent this performance loss.
There are many reasons why athletes do not drink enough during exercise. Some athletes forget to drink because they focus too much on their training or race, others are afraid of stomach or intestinal problems. During exercise the ideal drink should be cool, have a good taste, and be readily available. Otherwise athletes won't drink enough of it to compensate for the fluid losses during exercise. When an athlete drinks water or juice with little or no salt in it, the desire to drink will stop before the athlete has drunk enough.
How much should an athlete drink?
The amount of fluid that athletes need during exercise varies from person to person and depends on the weather conditions, so it is not possible to prescribe the same drinking protocol for everyone. When it is known how much water an athlete loses during exercise an individual plan can be made to reduce the amount of dehydration or to become hydrated again after exercise.
Drinking before exercise
It is not uncommon for athletes that they start their training or competition with a water deficit4. In warmer temperatures and if the effort lasts longer than ~60 minutes, this may have a negative effect on their performance. So it is important to start a workout or competition in fluid balance. If you are dehydrated before a race or training, drinks or snacks that contain a little salt can help to retain the fluids you take and encourages you to drink enough2 3.
Drinking during exercise
Drinking during exercise is important in all sports, including sports performed in water, such as swimming and water polo, or sports that take place in a cooled environment. It is important to drink regularly small amounts to limit dehydration to 2% of your body weight. A little salt can be added to the drink if you sweat a lot, in efforts lasting more than 2 hours, and when you drink large amounts during exercise2.
Drinking after exercise
To promote recovery after training or competition the lost fluids should be replenished. Therefore you should take more water and salt than you have lost5. To return in fluid balance after exercise it is better to start drinking small amounts early during exercise then large amounts at once. Foods that contain a lot of water can also help you hydrate again. Watermelon, orange, celery or cucumber are examples of fruits and vegetables that contain a lot of water.
Water can be a good sports drink
Research has shown that athletes drink more when the drink is cooled (~15° C), has a good taste, and contains a small amount of salt. In addition, many sports drinks also contain 4-8% of carbohydrates to replenish your energy stores during exercise. Drinking a sports drink can already be beneficial during a strenuous 60 minutes effort. However, water is also a good option during exercise. You should keep in mind that water alone doesn't stimulate you to drink enough. Soda and fruit juices often contain 10% or more carbohydrates and almost no salt, this slows down the water absorption into the gut which makes them less suitable as a sports drink.
It is also possible to drink too much. This can cause intestinal or stomach discomfort, but also in extreme cases it can change your sodium balance in the blood, this situation could be life threatening.
Electrolytes in sports drinks
Nowadays, it is recommended to reduce salt intake to reduce the load on the kidneys and cardiovascular system. A lower salt intake can also reduce the risk of high blood pressure. Whether these recommendations also apply to athletes is another story. During prolonged exercise athletes lose significant amounts of salt through sweat, this loss must be replenished. For those who have a low risk of high blood pressure, salt loss during exercise should be included in the recommended daily salt intake1. Other electrolytes (vitamins and minerals) that can be found in many sports drinks have no major impact on the water balance.
1. Pescatello, L. S., Franklin, B. A., Fagard, R., Faguhar, W. B., Kelley, G. A., & Ray, C. A. (2004). American College of Sports Medicine position stand. Exercise and hypertension. Medicine and science in sports and exercise , Mar;36(3):533-53.
2. Sawka, M. N., Burke, L. M., Eichner, E. R., Maughan, R. J., Montain, S. J., & Stachenfeld, N. S. (2007). American College of Sports Medicine position stand. Exercise and fluid replacement. Medicine and science in sports and exercise , 39(2):377-90.
3. Shirreffs, S. M., & Sawka, M. N. (2011). Fluid and electrolyte needs for training, competition, and recovery. Journal of Sports Sciences , 29 Suppl 1:S3-4.
4. Shirreffs, S. M., Sawka, M. N., & Stone, M. (2006). Water and electrolyte needs for football training and match-play. Journal of sports sciences , 24(7):699-707.
5. Shirreffs, S. M., Taylor, A. J., Leiper, J. B., & Maughan, R. J. (1996). Post-exercise rehydration in man: effects of volume consumed and drink sodium content. Medicine and science in sports and exercise , Oct;28(10):1260-71.