Sports Drinks: Hypertonic, Hypotonic or Isotonic?
We know we’re meant to consume at least 2 litres of water a day; but why is hydration so important to maximise performance?
Hydration forms a key part of a balanced diet, although its impact upon performance is often overlooked. Water is a vital component of the diet as the body is made up of around 70% water. With 85% of the brain made up of water; blood at 90% and muscles at 72%; water is essential to maintain hydration and bodily functions.
When exercising we lose fluid in the form of sweat to keep our body temperature at a desired 37oC, this is what we call thermo-regulation. Water is usually sufficient to use during exercise, however, for intense exercise or that that lasts longer than an hour you may need to use sports drinks to replenish hydration levels, carbohydrates, salts and minerals. Hypotonic drinks are great for rapid hydration as they are a thinner density than blood and are great for quick rehydration. According to Cohen, hypotonic drinks don’t usually contain electrolytes and therefore aren’t optimum for exclusive use during long bouts of exercise of over 30 minutes. Isotonic drinks, however, do contain electrolytes and carbohydrates which allow them to work well for longer periods of exercise. They can be absorbed relatively quickly as they have a similar density to blood.
Hypertonic drinks, however, are best used either after or several hours prior to exercise as they are absorbed more slowly than isotonic and hypotonic sports drinks. They have a high concentration of carbohydrates so can either be used to replenish glycogen stores after an endurance event or as part of ‘carbo-loading’ prior to sport.