Hydration and Performance

15th September 2015

By Anita Bean BSc RNutr – Human Race Hydration Expert

During exercise, staying hydrated is crucial for achieving peak performance. It may surprise you to know that about 75 per cent of the energy you put into exercise is converted into heat, and is then lost. This extra heat has to be dissipated to keep your core body temperature within safe limits – around 37 to 38°C. Your body keeps cool by sweating, which makes the replacement of fluids crucial. If you don’t replace at least some of your sweat losses you will quickly become dehydrated, which can affect not only your comfort levels but also your performance. Common symptoms of dehydration include lack of energy, nausea, early fatigue and inability to concentrate If allowed to progress, dehydration can have more serious health consequences.

Before exercise

Your main priority is to ensure you start a workout or race hydrated. This way you’ll have the best chance of putting in your best performance.

Aim to drink 5 -7 ml of fluid per kilogram of body weight about 4 hours before exercise – equivalent to 300 – 420ml for a 60kg person, or 350 – 490 ml for a 70kg person (1). That way you’ll have enough time for your body to excrete what you don’t need before you begin exercising.

You can monitor your hydration status by checking the colour of your urine. A pale straw colour indicates good hydration. If it’s darker then that’s a sign that you need to drink more fluid before you start exercising.

During exercise

There are no hard and fast rules about how much to drink but for most workouts and climates, 400 – 800 ml per hour will prevent dehydration as well as overhydration. You should listen to your body and drink when you are thirsty (2).

Aim to consume fluids at rate that keeps pace with your sweat rate. You’ll sweat more in hot and humid condition and when working out harder/ faster. It’s better to drink little and often say 100 – 150 ml every 15 minutes, as this will result in greater retention and less urination.

If you’re exercising for less than an hour, plain water is all you need to keep hydrated. If you’re exercising for longer than an hour, drinks containing up to 6g carbohydrate per 100ml can help keep you going for longer as the carbohydrate provides extra fuel for your muscles and speeds up water absorption. Vita Coco coconut water, squash or sports drinks are suitable. Extra sodium in the form of sports drinks is not necessary for exercise lasting less than 2 hours as it does not speed fluid delivery during exercise (1, 3, 6).

After exercise

The sooner you start to replace the fluid the sooner you will recover. So make drinking your priority immediately after exercise.

The exact amount you need to drink depends on how dehydrated you are after exercising. Weigh yourself before and after exercise. For each 0.5 kg (1 lb approx) of body weight lost, drink 600 – 750 ml of fluid (4, 5) but not all in one go.

Drink little and often, say, 100 – 150 ml every 10 or 15 minutes over the next hour or so until your urine is very pale yellow.

Both water and sodium need to be replaced to restore normal fluid balance after exercise. This can be achieved either by consuming a sports drink (which contains sodium) or any other drink (e.g. water, Vita Coco) plus accompanying food (that naturally contains sodium) if there is no urgency for recovery (6).

Vita Coco coconut water promotes rehydration as well as refuelling as it provides carbohydrate as well as fluid. The problem with water is that it increases urine output and reduces thirst and so may stop you drinking before you are rehydrated. Vita Coco Coconut water not only rehydrates the body effectively but research has demonstrated that it rehydrates just as well as a sports drink following endurance exercise (7, 8, 9)

(1) Sawka M.N. et al (2007), ‘American College of Sports Medicine Position stand. Exercise and fluid replacement’. Med Sci Sports Exerc, vol 39 pp 377 – 390.

(2) Noakes, T.D. (2010) ‘Is drinking to thirst optimum?’ Ann Nutr Metab. Vol 57 Suppl 2:9-17

(3) Jeukendrup AE et al (2009) Effect of beverage glucose and sodium content on fluid delivery. Nutr Metab (Lond). 2009 Feb 20;6:9.

(4) International Association of Athletic Federations (IAAF) (2007), Nutrition for athletics: The 2007 IAAF Consensus Statement.

(5) Shirreffs S.M. et al. (2004), ‘Fluid and electrolyte needs for preparation and recovery from training and competition.’ J Sports Sci. vol. 22 (1), pp. 57–63.

(6) Shirreffs, S.M. & Sawka, M.N (2011), ‘Fluid and electrolyte needs for training, competition, and recovery.’ J Sports Sci., vol. 29 suppl1, S39 – 46.

(7) Ismail I, Singh R, Sirisinghe RG. Rehydration with sodium-enriched coconut water after exercise-induced dehydration. Southeast Asian J Trop Med Public Health. 2007. 38(4):769-85.

(8) Saat M, Singh R, Sirisinghe R, Nawawi M. Rehydration after Exercise with Fresh Young Coconut Water, Carbohydrate-Electrolyte Beverage and Plain Water. Journal of Physiological Anthropology and Applied Human Science 2002; 21(2):93-104.

(9) Kalman D, Feldman S, Krieger DR, Bloomer RJ. Comparison of coconut water and a carbohydrate-electrolyte sport drink on measures of hydration and physical performance in exercise-trained men. J Int Soc Sport Nutr. 2012. 9:1.