Hydration: A Simple Guide to Improve Performance

Dehydration has negative consequences for performance, including poor concentration and reduced strength and endurance, and for health, including cramps, dizziness and exhaustion. Long, high-intensity exercise sessions can accelerate fluid loss through sweating, but the conditions that most increase dehydration risk are high temperature and humidity 1. An appropriate hydration strategy can therefore help prevent dehydration and maintain sports performance.

How should I hydrate before exercise?
Pre-exercise hydration recommendations are necessarily general because fluid requirements and the conditions affecting hydration status, such as the environment, vary greatly. It is therefore essential to avoid the onset of dehydration symptoms: dark urine, dry mucous membranes, eye twitching, sunken eyes, absence of tears and, of course, thirst 1,2.
Although requirements must be individualized, a general recommendation is approximately 6-8 ml/kg of body weight 2 hours before exercise. If signs of dehydration begin to appear, consume around 3-5 ml/kg of body weight 15-30 minutes before exercise.
A slightly higher sodium intake of 500-1000mg/L may stimulate thirst and increase fluid intake 3–5. Optimal electrolyte amounts can also help prevent exercise-associated hyponatremia, or low blood sodium, 3–5.
For example, these fluid and sodium targets could be reached with 0.5L of water plus 250-500mg of sodium, using an appropriately formulated electrolyte drink or a combination of water and electrolyte capsules.

How should I hydrate during exercise?
Hydration recommendations vary with weather conditions. Avoiding thirst during exercise is essential. It is also important to practice with and test different drinks during training to ensure they do not cause gastrointestinal problems 3–5.
A general target is approximately 0.4-0.8L/h of exercise, or similarly, 150-200ml (1 glass) every 15 minutes. High temperature and humidity increase fluid needs above these targets 3–5.
For exercise lasting less than 1 hour, water alone is generally sufficient. Longer sessions require drinks containing carbohydrates and electrolytes —450-700mg/L of sodium plus 80-200mgL of potassium—3–5. Carbohydrate-electrolyte drinks may improve water absorption compared with water alone, supporting hydration 6. Carbohydrate intake during exercise can also improve aerobic capacity and performance while reducing perceived exertion 7. Electrolytes such as sodium increase fluid retention and help prevent hyponatremia.
Finally, cold fluids at 15-22ºC may help limit the rise in body temperature under adverse environmental conditions 1.
Exercise requirements can be met, for example, by combining 0.5-0.6L of water, electrolyte capsules and carbohydrate sources such as gels, or by consuming 0.5-0.6L of a well-formulated carbohydrate-electrolyte drink.

How should I hydrate after exercise?
Restoring fluid balance is essential for recovery, particularly when fluid losses are high. Total volume must be individualized according to body-weight loss. Consume between 125% and 150% of the body weight lost, equivalent to 1.25-1.5L of fluid per kg of body weight lost 3–5. A general recommendation is 0.5L immediately after exercise. After this initial intake, consume one glass—200-250ml—every 15 minutes until reaching the recommended total volume.
Electrolyte replacement, including around 200-300mg of sodium, is also essential to maintain appropriate blood sodium and retain the fluid consumed 3–5.
These requirements can be met with approximately 0.5L of a carbohydrate-electrolyte drink, or by combining 0.5L of water, electrolyte capsules providing 200-300mg of sodium, and carbohydrate-rich solid foods or products.

Conclusion
A hydration strategy before, during and after exercise benefits health and performance, especially in high temperature and humidity.

AUTHOR

Lucas Jurado Fasoli – PhD in Biomedicine (UGR), dietitian-nutritionist, researcher at the Joint University Institute for Sport and Health, and assistant professor in the Department of Physiology at the University of Granada.

References
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2. Armstrong, L. E., Kavouras, S. A., Walsh, N. P. & Roberts, W. O. Diagnosing dehydration blend evidence with clinical observations. Current Opinion in Clinical Nutrition and Metabolic Care vol. 19 434–438 Preprint at https://doi.org/10.1097/MCO.0000000000000320 (2016).
3. Sawka, M. N. et al. Exercise and fluid replacement. Medicine and Science in Sports and Exercise vol. 39 377–390 Preprint at https://doi.org/10.1249/mss.0b013e31802ca597 (2007).
4. McDermott, B. P. et al. National athletic trainers’ association position statement: Fluid replacement for the physically active. Journal of Athletic Training vol. 52 877–895 Preprint at https://doi.org/10.4085/1062-6050-52.9.02 (2017).
5. Burke, L. M. & Hawley, J. A. Swifter, higher, stronger: What ’ s on the menu? Science (1979) 787, 781–787 (2018).
6. Maughan, R. J. & Murray, R. Sports drinks: basic science and practical aspects. (CRC Press, 2000).
7. Rollo, I., Gonzalez, J. T., Fuchs, C. J., van Loon, L. J. C. & Williams, C. Primary, Secondary, and Tertiary Effects of Carbohydrate Ingestion During Exercise. Sports Medicine 50, 1863–1871 (2020).

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