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Hydration and exercise.

“Check the colour of your wee”.


Unfortunately yes. That is the clear instruction BUPA have given me to determine whether or not I am sufficiently hydrated. So, despite having about 4.8 gazillion other things I’d rather do with my time, I must now dash to the little girls room and assess against a colour chart the exact shade of my…wee (I trawled the Dictionary of Synonyms, but frankly no better options, so we’ll just have to stick with ‘wee’ for now).

I won’t go into any detail about my personal findings, simply not necessary.

But I will tell you what to look out for in yours:

If you’re doing just fine and are already sitting at the top of the chart with perfect coloured wee, then great, clever old you. If you’re sitting somewhere nearer the bottom of this elegant little droplet diagram, then you gotta get guzzling. Let me tell you why…

Water is essential for life. The body is nearly two thirds water. So

whether you’re a serious athlete or a weekend warrior, it’s important to make sure you get the right amount of water (ideally filtered) before, during, and after exercise.

Without exercise, we should be drinking 25 – 28ml of water per KG of body weight.


A lady weighing 9 stone should be drinking on average 1.4 litres of water (9 stone = 57 kg, so 25ml x 57kg).

A man weighing 12 stone should be drinking on average 2.1 litres of water / day (12 stone = approx. 76kg, so 28ml x 76kg).

In addition to that, the advice is that you need between 400 – 800ml water per hour of exercise (volume/intensity depending).

Water regulates your body temperature, lubricates your joints, fuels your muscles and heals them. It also helps transport nutrients to give you energy and keep you healthy. If you’re not properly hydrated, your body can’t perform at its highest level. Slight dehydration, even as little as 2% (which is often not even enough to make you feel thirsty) can affect physical performance by 20%.

If you’re dehydrated before you even start exercising:

  • your core temperature will rise faster

  • your heart will have to work harder than usual

  • your running pace and reaction times will probably be slower

  • you may not be able to cover as much distance

  • energy / strength / power can diminish

By now you’ve probably got the gist: to perform well, you’ve got to drink.

Before exercise:

It can take time for fluids to be absorbed into your body, so drink steadily during the day and aim to drink around 500ml of fluid at least four hours before you exercise. In the 10 to 15 minutes before you exercise, top your fluid levels by drinking about half of this again.


Drinking little and often rather than a lot, less often, will give you the best chance of ‘smashing your goals’ (Will’s lingo, not mine). How much you imbibe (my lingo, not Will’s) will depend on how much you’re sweating and how long you’re exercising for. Just remember, your muscle cells are almost three-quarters water so if you're short on fluids, you really will feel the strain.


You can just listen to your body and drink for as long as you’re thirsty. But if that’s too laid back an approach (for the more serious athletes amongst you) then try this method to determine exactly how much to drink to compensate for fluids lost during exercise:

Is water good enough, or do I need a sports drink?

If you’re exercising for less than an hour, water is probably all you need to keep hydrated. So if it’s ‘office basketball’ in your lunch hour (throwing balls of paper from your swivel chair into the bin) then maybe, just maybe, you won’t need an energy drink to replenish you.

If you’re exercising for longer than an hour, sports drinks or even just squash can help you keep going for longer. As well as replacing lost fluid, they contain carbohydrates (sugar) and electrolytes. Electrolytes are the substances (sodium, potassium, magnesium and chloride) that salts break down into when they dissolve in fluid.

NB Drink them after you start exercising rather than before because it’s only when you start sweating that you lose electrolytes and need energy.

Types of sports drink:

There are three main types of sports drinks: hypotonic, isotonic and hypertonic.

  1. Hypotonic drinks are low in carbohydrates (less than 4g per 100ml) and are designed to replace the fluids you lose during exercise.

  2. Isotonic drinks contain a moderate amount of carbohydrate (4 to 8g per 100ml). As well as helping to replace fluid, they will also go some way towards topping up your body’s carbohydrate stores. These can sometimes get low if you exercise for more than an hour.

  3. Hypertonic fluids have a high concentration of carbohydrate (8g or more per 100ml). Your body absorbs them more slowly than plain water but it will give you a boost with refuelling.

Here’s a guide if you want to try making your own versions:

Can you drink too much?

Drinking too much can potentially be harmful as it can cause a rare condition called hyponatraemia. This is when you drink more fluid than you lose. The excess water dilutes the salts in your body and your cells swell up, which can cause a number of problems. You would really have to drink a lot for it to develop, but I have to mention it…

I don’t however want to end on a low, so just remember this “life saving” top tip:

When the going gets tough and the tough just can’t keep going, there’s no need to lose face…just pull out the “ I need a quick water break” line…it works every time. Or so I’m told…


British Nutrition Foundation


Ben Coomber


I am not a dietician or a nutritionist, and make no claims to the contrary. What is written on this site should not be taken as fact or advice. It is merely an opinion blog.

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