How To Hydrate For Running

Take on the right fluids to stay healthy and smash your race PB

Water, water everywhere
According to a study in the European Journal of Applied Physiology, the world's top marathon runners sweat at a rate which exceeds the intestinal absorption capability of the gut. In other words, they shed water faster than it's physically possible to replace it. Of course, even if you're struggling to complete 10k in two and a half hours, rather than 26 miles, staying well-watered is vitally important for both your health and performance. Use MH's definitive long-distance running hydration guide to guarantee a watertight race.


Over-consumption of water in the days and hours before an event is a common mistake which, counter-intuitively, can leave you feeling parched at the start line. This is because the body senses the huge amount of liquid you're suddenly downing and releases a diuretic hormone in an attempt to bring your fluid levels back to normal. In the short-term, this reactive offloading (your half hourly flights to the bathroom) can be over-compensatory, leaving you dehydrated at the worst possible time. "The best thing to do is sip regularly before the race," says sports nutritionist Alexandra Rees. If you start to get a 'sloshing' feeling in your stomach, you've drunk too much – but frequent small sips should help you avoid this. "Bear in mind that if you feel thirsty, you're already dehydrated," adds Rees.

The very real dangers of over-hydration have not been communicated effectively enough in the past. A recent study in the British Journal of Sports Medicine highlighted the case of a runner in the London marathon who collapsed and died, after crossing the finish line, due to exercise-associated hyponatremia (EAH) – caused by an increase in total body water leading to a low concentration of sodium in the blood. More common in cooler conditions, you'll cut your EAH risk hugely by sipping on a sports drink containing sodium and electrolytes alongside plain water – and upping your salt intake in the days before a race (heart-health permitting) can also help. At the very least, drinking excessively will severely impact your performance. "If you're carrying an extra litre of water you've not lost any power but you are, of course, 1kg heavier and therefore probably at least 10% slower," says Tim Lawson, director of Science in Sport.

While the sun has a predictable effect on the amount you sweat, the Strength and Conditioning Journal says it's running in the cold that you really need to look out for. Here, "the [body's] thermoregulatory response includes enhanced heat production by a variety of means; all resulting in increased fluid losses". So, If the race-day climate inspires jealousy of fun-runners in warm bear costumes, up your fluid intake accordingly. Be advised that the journal also notes marathon runners competing on particularly hot days can lose up to 5% of their bodyweight. A study in the Journal of Sports Sciences found dehydration resulting in a 3% body mass reduction adversely affects short duration sprinting speed – so staying better hydrated than a running partner is vital if you're to pip them at the line.
"Take full advantage of every drinks station, but don't chug back the whole bottle," advises Rees. "Take some swigs, see how it feels on your stomach, and think about how much you're sweating." As for gels, be sure you know how your body copes with them. "Most need to be taken on board with at least 500ml of water, and that's a lot of liquid to have sloshing around your stomach," adds Rees. "If you can take on a gel without any gastrointestinal distress then by all means use them, but test them first on training runs before swallowing one during the race and puking over yourself at mile 10."


Replacing lost fluid and electrolytes immediately post-run is crucial for lessening debilitating stiffness and muscle pain – and it'll also reduce the risk of your weakened body being struck down by illness. "To replace your electrolytes, combine water and fruit juice in equal measures, adding a 1/4 teaspoon of sugar," advises Rees. "To help muscle atrophy, you need protein in a huge way so you're not walking like John Wayne for the next seven days. The best ratio is three parts carbohydrates to one part protein.

Research from the University of Bangor found downing a good recovery drink (such as REGO) immediately after exercise maintains your immune function at its pre-exercise levels. Waiting an hour or downing a carbs-only beverage, on the other hand, can leave it severely compromised.

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