Hydration

Hydration is the process of maintaining an adequate amount of body water to support physiological functions. It involves consuming fluids to replace water lost through sweating, breathing and elimination so that the body’s water content remains within a healthy range.

Importance of proper fluid balance

Approximately 45–75% of a person’s body weight is water, and this fluid acts as a transport medium, lubricant, and temperature regulator. During daily life and exercise, water is continuously lost through breathing, urine, stool and sweat. Physical activity increases these losses; during a hard training session an athlete can lose 0.5–2.0 litres of sweat per hour and, in extreme conditions, even more. Sweat also carries sodium and other electrolytes, so prolonged sweating can disturb both fluid and mineral balance. A deficit greater than about 2% of body weight is considered dehydration and is associated with reduced endurance, increased core temperature and impaired cognition. To maintain euhydration, athletes should match fluid intake with sweat losses. Drinking about 500 ml of fluid two to three hours before exercise, followed by about 200 ml every 15–20 minutes during activity, helps prepare the body for exercise and supports performance. After exercise, drinking enough to replace the weight lost – generally around 500 ml within two hours – promotes recovery.

Practical hydration guidance

For short sessions lasting less than an hour, plain water is usually sufficient. When exercise continues beyond an hour or includes intense intervals, a beverage containing electrolytes and moderate carbohydrate helps replace both fluid and sodium while providing energy. Recognising the signs of dehydration, such as thirst, a dry mouth or dark urine, can prompt timely drinking. Athletes should consider environmental conditions, clothing and individual sweat rate when planning fluid intake. Weighing before and after training provides a simple way to estimate sweat loss: each kilogram of body mass lost reflects roughly one litre of fluid.

Maintaining fluid balance is fundamental to sports performance and health. By monitoring sweat loss and replacing both water and electrolytes, athletes can support endurance, regulate body temperature and reduce the risk of cramps or heat-related illness. A thoughtful hydration strategy is therefore a basic part of any training plan.

Related Terms: Euhydration, Dehydration, Hypohydration, Rehydration, Sweat rate