Wednesday, October 27, 2021
Spartan Race

Hydration advice for runners

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Sarah Martin-Crake
Sarah's a dietitian and sports nutritionist, with years of clinical experience in the NHS and her Dorset-based private practice. Sarah has a passion for running, swimming, the great outdoors and cheese.

What you drink can have a huge impact on your running. Drinking isn’t a difficult thing to do, but getting it right can be tricky, and getting it wrong can be dangerous. So, what should you drink and how much? Find out in this ultimate guide to hydration for runners.

Signs of dehydration

Fluid change in the body is a pretty constant process. We breath, we pee, we poop, we metabolise, we sweat… all of which result in fluid loss. On the other hand, we eat and drink, which results in fluid gain. There are all kinds of biochemical tests you can undertake to measure hydration status, but for the healthy individual who wants to make sure they are well hydrated, these really aren’t necessary. The easiest way to check roughly how well hydrated you are, is to look at the colour of your pee. The darker your pee, the more likely it is that you are dehydrated.

You should aim to keep your pee a nice light colour, often described in the medical world as ‘pale straw’.

Pee colour chart

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Other than pee, the most obvious sign of dehydration is thirst. The healthy body usually maintains fluid balance fairly closely. One of the key mechanisms for this is to make you feel thirsty.

Other signs to look for are a dry mouth and thick saliva. And as things progress, you might stop sweating. If you do, this isn’t a good sign. By now, you’re pretty dehydrated. You may also be suffering from a heat injury, so rehydrating and getting out of the sun are essential.

Pee in the morning is usually on the darker end of the chart, and this is usually due to the fact that most people have slept through the night without having a drink. Now, bearing in mind that most races take place in the morning, you ideally want to make an effort to be well hydrated before you get to the start line. Once running, the increase rate of sweating and all of the heavy breathing will deplete your body of fluids even further. Dehydration and good athletic performance do not go hand in hand.

What should you drink?

Plain water? Water with electrolytes? A specialist sports drink? Cocktails? Probably (definitely!) not the latter. At least not until the race is run!

If you are dehydrated – have dark urine, are thirsty, etc – then pretty much any fluid will do the job. A glass of water, some squash or fruit juice, even a cup of tea or coffee will do the job. Whilst caffeine does have a dehydrating effect, this is usually more than offset by the actual amount of fluid you consume.

Sports drinks that contain electrolytes and, sometimes, carbohydrates, will also do the job perfectly well. But if you are reasonably well hydrated already, they aren’t strictly necessary. Sports drinks do hydrate better than water (they contain electrolytes which help your body to absorb water), so if you’re a bit dry, they’re a good choice. If they contain carbs, they’ll also top up energy supplies.

As to how much to drink, your thirst is usually a good indicator. It’s impossible to state a specific volume that will bring you back to being hydrated, so drinking when you are thirsty is a good rule to go by. Drinking huge amounts isn’t necessary. Nor is it safe. There are risks associated with over-drinking. From the minor needing to pee at the most inopportune moments (pre-race toilet queues and mid-run Portaloo stops aren’t much fun), to the serious and potentially life-threatening – hyponatraemia.

Risks of over-hydrating – hyponatraemia

First, a word about peeing. When we pee, we excrete by-products of metabolism – the soluble waste our body doesn’t need. One of things we pee out is sodium, which helps our body to maintain fluid balance and blood pressure, among other things. When we lose too much sodium, these processes stop working effectively.

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When sodium levels start to drop, we tend to feel fatigued and lethargic. Clearly not conducive to a quality race or training session. As levels drop lower, hyponatraemia can develop. This can be exacerbated if you are a salty sweater. How can you tell? A salty taste to sweat, and salt deposits on the skin are tell-tale signs.

Hyponatraemia is a condition that can occur when you drink too much. If the body is overloaded with fluid, to the point where you can’t pee it out quickly enough, then fluid can build up in places it shouldn’t be. The worst case scenario is that this fluid build-up occurs in the brain, which can result in headache, confusion, loss of consciousness, and death. There are cases reported every year from sporting events of runners dying from hyponatraemia. While it’s not exactly common, it certainly is a risk and one to be avoided.

Drinking fluids that contain electrolytes helps to reduce the dilutional effect of drinking too much water. Sports drinks and anti-diarrhoeal sachets will both help to reduce the effects of sodium loss, but sports drinks are probably more appealing!

Top tips

    • Aim to be hydrated before the race starts. If it’s particularly hot, or if you sweat a lot, check the colour of your pee and perhaps increase fluid intake by a cup or two per day, for a couple of days pre-race.
    • On race day, purposefully drinking lots isn’t necessary. The fluids will slosh in your stomach as you run, and leave you hunting for a toilet.
    • In particularly hot weather, your fluid losses through sweating increase. Running in warmer temperatures therefore can require more fluid intake to off-set the losses. You don’t need to force yourself to drink, but taking a water bottle or hydration pack with you on a run will give you access to fluids you can sip at, as and when you want/need to. As well as keeping you more comfortable, drinking can help to cool you down and prevent heat injury.
    • Drink to thirst. This strategy doesn’t replace all lost fluids, but is usually enough to keep you sufficiently hydrated to complete your run without detrimental effects on your performance.
    • Beforehand, drink anything you fancy, except alcohol!
    • During a run, opt for a drink that contains electrolytes.
    • After a run a celebratory beer is just fine, but keep an eye on the colour of your pee! All other drinks will help to bring you back to an adequately hydrated state. Drinks that contain electrolytes will help your body to reabsorb water, and if they contain protein and carbs too, you can replenish energy stores and promote recovery all at the same time.

Holding cup of water

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