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My hydration:  race fuelling strategy for a Half-Marathon by Peter Thomson

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Hydration is an important component of performance in running and I, like most runners, have been encouraged to hydrate well and to maintain hydration through regular fluid intake and particularly by actively rehydrating after a run or race.

It is estimated that in average British running conditions (cool and grey) that the average runner loses about 1 litre of fluid per hour. This is known to vary widely between individuals. So essentially during a Half Marathon I could expect to lose about 1.5 to 2.0 litres. However more recently there have been increasing concerns about the risks of over-hydration leading to cerebral oedema (brain swelling) and fatalities. The advice now is to drink when you feel thirsty and don’t expect to be fully hydrated when you finish the race. It probably won’t have affected your performance significantly so says Prof Goulet, a renowned Canadian Exercise Physiologist in a recent 2013 review article (British Journal of Sports Medicine 2013; 47:679-686)

What was my preparation and strategy when training for a Half Marathon?

During training I probably never ran a full 21km and therefore only drank whilst running toward the end of my preparation to ensure that I could swallow fluids comfortably whilst on the run – not easy to coordinate breathing and swallowing. I always have a cup of tea before a training run. Although I am not aware of any clear scientific proof of the benefits of tea drinking in runners, it has been practised by East African athletes for many years and I find it refreshes and energises me first thing in the morning.

On Race Day I first remind myself that a Half Marathon is only two 10km races back to back so hydration is not critical unless the conditions are extremely hot and dry.
I have a particular pre-race morning regime of a morning cup of tea, followed at breakfast

(Race Start minus 2 hours) by 4 slices of toast with margarine and jam or honey, washed down with a couple of mugs of strong black filter coffee. Theoretically coffee is supposed to have a diuretic effect (pushing water out of your kidneys and dehydrating you) however remember a Half Marathon is only two 10km runs not an ultra-endurance race hwere hydration may be more critical. The advantage of black coffee is that it activates your free fatty acids firing them up. They form part of the glucose /fatty acid fuel mix which your body will use after only a few minutes of running.

Endless drinking before the race only results in the discomfort of a full bladder and an urge to relieve oneself – often behind a tree as once in the race pens there is limited access to “porta-loos”. My advice is forget it.  If my urine was a pale straw colour before I left home for the race, there was no need to continue hydrating up to the start of the race. Running without fluid sloshing around in your stomach, makes for a more comfortable experience with less risk of abdominal cramps and nausea during the race.

During the race I avoided drinking until about half- way when I would down about 250mls of water. By mile 9 I’ll take a couple of gels containing a mixture of fructose and glucose, with added sodium, and wash them down with 250mls of water from the water station. Jentjens et al showed that a glucose/fructose combined fuel give a higher energy yield than glucose alone, sparing the body’s own store of glycogen, although this is really only valuable when exercising for more than 2.5hrs. Two more gels around mile 11 with water (they also contained a small amount of caffeine which gives me an boost) and then to the finish, tired yes but not exhausted from lack of fuel or nauseous from drinking too much fluid. Good result.

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