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Hydrate to perform

Updated: Jul 5, 2019

For athletes in any sport, making sound nutrition choices is often a major priority. However an area that is often missed, or rather oversimplified, is that of hydration. With the onset of summer (finally!) and popularity of recreational endurance events during this season, ensuring your clients stay optimally hydrated is crucial for effective performance. Water makes up around 70% of our body mass, and is an essential nutrient, without which we simply could not survive. In fact a 12% of bodyweight water loss is usually fatal, however such drastic losses are usually addressed before reaching this stage (Popkin, D’Anci, & Rosenberg, 2010).

Dehydration and performance

Losing water during exercise is an unavoidable consequence of heat regulation through sweating and increased respiration. Despite our best attempts to address the balance through water consumption, we often begin to dehydrate. Once this happens, various physiological functions become impaired, leading to negative effects on physical performance. Early signs of dehydration include; headaches, fatigue, dry eyes, loss of appetite and dark urine with a strong odor. More severe dehydration which needs urgent medical attention can lead to; clumsiness, muscle spasms, reduced vision, difficulty swallowing and delirium

A fluid loss of only 2% of body mass has been shown to cause a significant decrease in performance, with more severe decrements as dehydration levels increase. Later research has challenged this figure and now suggests that impaired performance may be seen with losses as low as 1-1.8% (Walsh, Noakes, Hawley, & Dennis, 1994).

Many systems exist to monitor hydration levels, including weighing and urine osmolality testing, although these can be expensive and time consuming. A simple solution for recreational athletes is to monitor urine color, comparing it against the chart below to see whether they are becoming dehydrated (aim for 1-2). This easy method means clients can keep track of hydration themselves and intervene if a shift into dehydration is observed.

Is water enough?

On a day-to-day basis, consuming the recommended amounts of water alongside fluid taken on from food (approximately 1-1.5 litres comes from food) is satisfactory for the average sedentary person. However this is not sufficient for those taking part in strenuous exercise or endurance events, especially in hot conditions.

Alongside water loss, sweating during prolonged exercise leads to a loss in electrolytes and carbohydrates, both essential for bodily functions and fluid retention. For this reason, sports drinks contain both of these in various amounts.

Types of sports drink

Commercially available sports drinks vary depending on their carbohydrate content, which one you might use depends on the intensity and duration of exercise.

Hypotonic drinks contain less than 4g of carbohydrates per 100ml, however this small amount means it will hydrate you more rapidly than water, making them good for lower intensity workouts or less than 60 minutes.

Isotonic drinks contain an amount of carbohydrates and electrolytes equivalent to that in the body meaning they are suitable for replacing fluid and fuel lost during prolonged high intensity workouts/ events longer than 60 minutes.

Hypertonic drinks contain a large amount of carbohydrates, meaning they are good for fuel replacement during long duration events, however they slow down fluid replacement, so should be taken on alongside water.

Making your own Isotonic drink

Rather than buying off the shelf products, it is possible to simply make your own Isotonic drink to keep you hydrated during extended high intensity workouts.

Simply add 200ml of concentrated Orange juice to 1 litre of water with a pinch of salt (1g), refrigerate and enjoy!

In summary, staying hydrated in the heat is key and those taking part in high intensity exercise will see greater fluid replacement by consuming an isotonic drink containing carbohydrates and electrolytes over plain water.


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Popkin, B. M., D’Anci, K. E., & Rosenberg, I. H. (2010). Water, hydration, and health. Nutrition Reviews, 68, 439-458.

Walsh, R. M., Noakes, T. D., Hawley, J. A., & Dennis, S. C. (1994). Impaired high-intensity cycling performance time at low levels of dehydration. International Journal of Sports Medicine, 15, 392–398.

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