Fluid can be excreted from the body in a number of ways:
- Sweat: When we sweat, the sweat evaporates, and carries the heat energy away from the body during exercise/in warm environments. This goes out into the air helping to maintain the body temperature at a safe level. i.e. sweating cools us down. As athletes, we can sweat out litres of water during training sessions and matches, and the amount will depend on various factors, including your physical attributes, activity intensity, length of the activity, and environmental heat and humidity.
- Urination: When we urinate our body is getting rid of waste products, controlling blood volume and controlling amount of electrolytes in the body. These are all well regulated, and don’t need a huge amount of conscious effort as it happens naturally. The amount of fluid that you lose through urination is largely dependant on the amount you drink. As well as being affected by other aspects like electrolyte levels and how much you are sweating.
- Other: Fluids are also lost through breathing (the air we breathe out is high in water vapour), and excretion.
Impact of Under-Hydration
- Heart Rate Studies have shown that athletes that do not consume water during a training session will have a significantly higher heart rate in comparison to athletes who have consumed water throughout the session, telling us that the same exercise session was more strenuous when under-hydrated.
- Temperature Regulation Sweat helps regulate body temperature by dissipating heat from the body i.e. it cools us down. When we’re dehydrated, we sweat less, and therefore the body will either increase in temperature to the point of causing harm, or you will be forced to reduce intensity due to the discomfort of overheating. Either way it will result in a negative impact on athletic performance.
- Electrolyte Levels Electrolytes are involved in carrying electrical impulses around the body, and are involved in the nervous system and contracting muscles, both of which are extremely important for athletes. They are also involved maintaining hydration levels in and out of the body’s cells. The main electrolytes include sodium, potassium, chloride, bicarbonate, calcium, phosphate, magnesium and others, all with their own functions. We lose some of these through sweat, and if we don’t replace them and they get too low, we can see issues with muscle cramping, fatigue, and ultimately a downturn in athletic performance.
General Daily intake
The amount you should drink will depend on a lot of factors, but generally about 1L per 25kg bodyweight (3L for a 75kg athlete) will be a good starting point, along with seasoning your food and eating plenty of fruits and vegetables, in order to ensure adequate electrolyte intake. Urine colour should also be monitored, ensuring regular, clear urinations throughout the day.
During matches and training sessions, aim for 1-2 mouthfuls every 10-15 minutes. This drink should be made up of water, with some electrolytes, and perhaps some carbohydrates (no more than 7% concentration) which can help with the gut’s absorption of the fluid, as well as allowing you to gain the performance benefits associated with carbohydrate supplementation.
After tough training sessions and matches, it’s important to start the rehydration process soon, which should involve sipping on either water, milk or an electrolyte drink.