Ask the coach: Being sick during a marathon

During my last marathon, I threw up at 23 miles and could not finish at my target marathon pace. Have I just not trained my stomach enough to handle the high quantity of gels? Or is this just a sign the target pace was just too much for my body? Is being sick during a marathon normal?

Glenn

Running coach answer: Being sick during a marathon

Being sick during a marathon always seems like a messy topic, but it is surprisingly common, with an estimated 60% of runners suffering a gastrointestinal problem, either the trots or being sick, during a training run or, more commonly, in a marathon.

So frequently, runners say I got a stitch in my race, but I had the same breakfast, food, drink, and gels, as I have practised with in training,

It has never happened to me in a race, although I do have to dive into the bushes every now and then in training. There are many high-profile cases of leading runners in major marathons having to break off for a break. This year I watched the London Marathon at the 6-mile drink station near Greenwich, where about 10 port-a-loos were positioned so that runners could get to them. At times all the cubicles were occupied – as a spectator I politely waited for the runner queue to quieten down before going myself (too much coffee while spectating in my case)!

From my brief research, it seems that digestion problems during exercise are most frequent in runners. This may be because of the effect of repeated foot strikes on the ground and the resultant shock wave, which moves the stomach contents around.

So what is going on?

What you eat before the race can make a difference. The high fibre content of your diet in the days leading to the race may cause visits to the loo – avoid heavy meals before a run.

One of the things that happens when you start to run is that the blood supply from some of your organs is diverted to your working muscles, reducing digestive activity and leaving stomach contents sitting around while you are running. Eat a light carbo-rich meal two to three hours before exercise so that the stomach empties before you start to run.

Running an endurance event can cause heavy sweating and fluid loss. Dehydration can cause muscle cramps, vomiting, and diarrhoea, which in turn cause further dehydration. Take care of hydration levels before exercise, particularly in the intense environment of a race.

For any race over 90 mins, it is recommended that runners keep their glycogen levels up with 30 to 60g of carbs per hour. We tend to take gels as a convenient way of getting this energy in – they can be sickly and cause a tummy upset in some runners. It is possible that you are perfectly fine at a training pace and only experience feeling sick towards the end of a marathon. It is hard to replicate the stress your body feels during a marathon but by practising a pre-long run diet protocol and using the gels that you will use in the race during your long training runs, you can go some way to preparing the body.

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