Generally, the more a person sweats, the more they will need to drink. Average sweat rates are estimated to be between 0.5–2.0L/hour during exercise.
Dehydration can cause tiredness and affect performance by reducing strength and aerobic capacity (especially when exercising for longer periods). So, especially when exercising at higher levels or in warmer conditions, it is important to try and stay hydrated before, during and after exercise to prevent dehydration. In most cases, unless training at a high intensity for over an hour, water is the best choice as it hydrates without providing excess calories or the sugars and acids found in some soft drinks that can damage teeth.
For those who are recreationally active to a high level, or for athletes, managing hydration around training or competition is more important. The higher intensity and longer duration of activity means that sweat rates tend to be higher. Again, the advice for this group would be to ensure they drink fluids before, during and after exercise. Rehydration would usually involve trying to drink around 1.25-1.5L of water for every kg of body weight lost during exercise through sweat. However for longer, more intense exercise (longer than 60 minutes), there may be extra benefit in consuming drinks containing some carbohydrates, and other electrolytes including sodium, during exercise, as this is when carbohydrate stores may substantially decrease, and sodium losses can be higher (such as marathon/long distance running, football games or competitive swimming).
Below are some examples of other drinks, other than water that may be used by athletes, both recreational and elite.
- Sports drinks: sports drinks contain carbohydrates in the form of glucose, as well as electrolytes such as sodium. Sodium will replace any that has been lost from sweating and enhance rehydration, and glucose will replenish carbohydrate stores. Sports drinks have been shown to help endurance performance and recovery for active individuals performing endurance exercise over a longer duration (60 minutes or more) (e.g. participating in a marathon). However, it is important to remember that sports drinks are like other soft drinks that contain sugars. This means that they can be high in calories and contribute to tooth decay, so they are only suitable if taking part in high-level endurance sports or if sweat loss is high.
Sports drinks can be expensive compared to other drinks; however it is easy to make them yourself! To make your own isotonic sports drink, mix 200ml fruit squash (containing sugar rather than sweeteners), 800ml water and a pinch of salt.
- Milk: Skimmed or semi-skimmed milk has been used in some studies as a post-exercise recovery drink. It contains minerals that can replace those lost via sweating, as well as providing nutrients involved in muscle function and bone health (potassium and calcium). It also naturally contains high quality protein and some carbohydrate in the form of lactose and is relatively cheap to buy.
Energy drinks: are not designed to replace the electrolytes lost in sweat and may contain other ingredients with stimulant properties, such as caffeine. As some are high in sugars, they can increase the risk of tooth decay and contain energy, which may cause weight gain if consumed in excess.