How To Drink Water During Sports
An advice for hydration to improve health and performance
Exercise is accompanied by an elevation of metabolic rate that will cause body temperature to rise if heat loss mechanism are not invoked. Hydration is known to regulate body temperature, primarily due to sweat loss. What are the effects of hydration for sports performance and how do you stay hydrated during exercise?
Dehydration causes an increase in body temperature [7]. Blood will flow to the skin as a cooling mechanism to keep the body’s core temperature stable. Because of this, less blood is available for the muscles and thus the heart will need to work harder to provide the muscles with enough oxygen and nutrients, which are needed in muscles during sports performance. How does dehydration affect endurance, sprint and cognitive performance?
Endurance performance
Endurance performance seems to suffer when dehydration of more than 2% of body mass occurs. Various studies have shown an significant higher heart rate (HR) and rate of perceived exertion (RPE) of dehydrated athletes in comparison with hydrated athletes after performing the same endurance exercise [2, 4, 6]. Also cycling time trial distance was 13% lower [6]. In cold air environments, dehydration levels can be higher before these effects occur [1]. In warm environments, dehydration will have a bigger impact on these effects.
Sprint performance
Mean values of various studies show that dehydration of more than 2% body mass causes a decrease in strength (2%), power (3%) and high-intensity endurance training (10%) [5]. The underlying processes of this decrease are not yet known.
Cognitive performance
Dehydration also has negative effect on cognitive function and mood [8, 10]. The effect size depends on the cognitive task performed.
Practical advice
Dehydration can happen in various ways. Next to drinking too little water, taking a bath the night before or ingesting alcohol, caffeine or salt have influence on your hydration status. How do you know your hydration status and how can you be sure you’re hydrated before exercising?
Pre exercise
Knowing your hydration status prior to exercise is important. A single measure of body mass can give no indication of hydration status, but measuring every morning will provide information on hydration status: morning body mass will fluctuate by less than 1% in well hydrated individuals who are in energy balance [9]. The color of urine is also a good indicator: more yellow urine indicates dehydration.
During exercise
The amount of water to drink during exercise depends on environmental factors and is different per individual. Getting into the habit of weighting before and after training is important to estimate sweat loss. Weight loss after exercise should not exceed 1–2% of body mass. If more than this has been lost, then you should drink more next time. If body mass loss was less than this, water intake was probably greater than necessary. With experience, you will become better at estimating the amount of water intake needed during a particular training or match. With this method, it is also possible to program your drinking beforehand. However, conditions could be different than expected and overhydrating could be possible. Drinking too much causes an unnecessary increase in weight and causes gastrointestinal symptoms. When setting up a drinking plan, a professional dietician should guide you.
Another method is called Ad Libitum drinking: drinking only when you feel thirsty during the exercise. One study showed that athletes will drink half the water with this method in comparison with a drinking plan [3]. Even though no significant negative effects were found, a drinking plan set up by a professional dietician is a more secure method.
Post exercise
After exercise, next to eating a nutrient and mineral rich meal rich, drinking 1.5x times more than your sweatloss 2 to 6 hours after exercise is important for recovery [11]. Drinking more than is lost is important, because the body will excrete part of the ingested water.
To calculate your sweat loss, the following example should be followed:
Weight before: 60kg.
Weight after: 59kg.
Weight loss: 1kg.
Water ingestion during race: 1L.
Sweat loss: weight loss + water ingestion = 2kg.
Amount of water to drink 2 to 6 hours after exercise: 2*1.5 = 3L.
In short
- Being hydrated is an important factor for optimal endurance, sprint and cognitive performance.
- Knowing your hydration status prior to exercise and being able to estimate water loss during exercise is essential to calculate water intake.
- Measuring weight every morning is the easiest way to calculate hydration status: a fluctuation of more than 1% indicates dehydration in persons who are in energy balance.
- Measuring weight pre- and post-exercise is the easiest way to calculate sweat loss. For recovery, water ingestion 2 to 6 hours after exercise should be 1.5 times the amount of sweat loss.
- Drinking too much also has negative effects.
References
1. Cheuvront, S.N., et al., Hypohydration impairs endurance exercise performance in temperate but not cold air. J Appl Physiol (1985), 2005. 99(5): p. 1972–6.
2. Cheuvront, S.N. and R.W. Kenefick, Dehydration: physiology, assessment, and performance effects. Compr Physiol, 2014. 4(1): p. 257–85.
3. Goulet, E.D.B. and M.D. Hoffman, Impact of Ad Libitum Versus Programmed Drinking on Endurance Performance: A Systematic Review with Meta-Analysis. Sports Med, 2019. 49(2): p. 221–232.
4. Green, J.M., et al., Effects of 2% Dehydration on Lactate Concentration During Constant-Load Cycling. J Strength Cond Res, 2018. 32(7): p. 2066–2071.
5. Judelson, D.A., et al., Hydration and muscular performance: does fluid balance affect strength, power and high-intensity endurance? Sports Med, 2007. 37(10): p. 907–21.
6. Logan-Sprenger, H.M., et al., The effect of dehydration on muscle metabolism and time trial performance during prolonged cycling in males. Physiol Rep, 2015. 3(8).
7. Maughan, R.J. and S.M. Shirreffs, Dehydration and rehydration in competative sport. Scand J Med Sci Sports, 2010. 20 Suppl 3: p. 40–7.
8. Petri, N.M., N. Dropulic, and G. Kardum, Effects of voluntary fluid intake deprivation on mental and psychomotor performance. Croat Med J, 2006. 47(6): p. 855–61.
9. Sawka, M.N., et al., American College of Sports Medicine position stand. Exercise and fluid replacement. Med Sci Sports Exerc, 2007. 39(2): p. 377–90.
10. Shirreffs, S.M., et al., The effects of fluid restriction on hydration status and subjective feelings in man. Br J Nutr, 2004. 91(6): p. 951–8.
11. Shirreffs, S.M., et al., Post-exercise rehydration in man: effects of volume consumed and drink sodium content. Med Sci Sports Exerc, 1996. 28(10): p. 1260–71.
