Dehydration and its Impact on Performance

It's widely accepted that dehydration affects performance. Exercise at any intensity will feel harder (increased RPE) and your time to fatigue will increase considerably. Yet, did you know that just 2% dehydration (equal to body mass) can affect performance (1)? Findings show that aerobic endurance is impaired by dehydration due to increased body temperature and raised heart rate (2). What is more, there is some suggestion that it could increase the use of carbohydrates for fuel (2), which will hence see energy stores depleted at a faster rate. This isn't just the case for endurance exercise either, dehydration can limit strength, power and high-intensity endurance (30secs-2mins) too (3). Hence, no matter what exercise you enjoy, staying hydrated is incredible important to maintain high levels of performance.

It's always important to ensure that we are properly hydrated prior to exercise to reduce our risk of dehydration during exercise. Bear in mind that during exercise thirst isn't always a good indicator of hydration status; we are often dehydrated before we feel thirsty, so be sure to rehydrate whenever you have the opportunity to do so.

What are the best fluids to drink?

Water is always the most suitable drink to go to, particularly for lower intensity and short duration exercise. However, for high intensity and endurance sports there is a significant benefit for performance if we add carbohydrates and electrolytes to water e.g. sports drinks. Carbohydrates added to water not only improve the taste so as to increase consumption but they provide a muscle energy source (4) to replenish glycogen stores during exercise. Electrolytes, such as sodium, are lost during high intensity exercise and so must be replenished during and after. The consumption of sodium in fluid improves fluid intake as it

stimulates the thirst and promotes both carbohydrate and water uptake in the intestines (4). Hence, consuming electrolytes post high intensity and endurance exercise will benefit recovery and post-exercise rehydration.

Tips for staying hydrated everyday

- Always have a water bottle with you.

- Add sugar free squash if you need to improve the taste.

- Don't drink for thirst, just drink as often as possible.

- Fruit consumption can be helpful for maintaining hydration levels.

(1) Murray, B., 2007. Hydration and physical performance. Journal of the American College of Nutrition, 26(sup5), pp.542S-548S.

(2) Barr, S.I., 1999. Effects of dehydration on exercise performance. Canadian Journal of Applied Physiology, 24(2), pp.164-172.

(3) Judelson, D.A., Maresh, C.M., Anderson, J.M., Armstrong, L.E., Casa, D.J., Kraemer, W.J. and Volek, J.S., 2007. Hydration and muscular performance. Sports medicine, 37(10), pp.907-921.

(4) Sports Dieticians, 2009. Fluids in Sport [online]. Sports Dieticians Australia. Available at: [Accessed 16th June 2021].

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