Athletes know that it is important to stay well hydrated during training and competition. Sports drinks are classed as either hypotonic, isotonic or hypertonic, depending on the concentration of carbohydrate in the drink. It is important to know the difference between the three and know when each should be used. Selecting the wrong type of drink could cause poor performance.
Hypotonic drinks contain around 2% carbohydrate so they are less concentrated than blood. They are absorbed almost as quickly as plain water. They would be beneficial for training or events lasting up to 90 minutes.
Isotonic drinks have the same concentration as blood, around 4-7% carbohydrate. They also normally include electrolytes such as sodium. They are absorbed quickly but still not as quickly as plain water. They give a combination of immediate energy from glucose, slightly delayed energy from sucrose and slower releasing energy from maltodextrin, making them ideal for training and competition lasting longer than 90 minutes.
Hypertonic drinks have a concentration higher than blood due to containing larger amounts of glucose or sucrose, usually at least 10%. The absorption rate is very slow and they can cause gastric distress and dehydration, but they can be useful in maintaining blood sugar levels in long endurance events.
Exercise, especially in hot and humid conditions, can cause large water losses through sweating. For this reason, people who exercise need to ensure they are well hydrated before exercising and consume fluids containing electrolytes, such as sodium and potassium, during and after training to replace lost fluid. This will minimise the risk of a reduction in performance or any detriment to their health.
Helen writes on all aspects of running, fitness and nutrition. Visit http://www.run-resource.blogspot.com to learn more