Training your gut

The theory is simple: It takes more calories to make it to the end of a marathon than your muscles are capable storing, so you need to take in some fuel during the race. Sports nutritionists suggest aiming for about 60 g of carbohydrate per hour of exercise, and as much as 90 g per hour for runs lasting longer than three hours. That’s easier said than done, though, as the porta-potties lining marathon courses attest. Gastrointestinal discomfort is one of the most common complaints reported by marathon and ultramarathon runners.

So how do you learn to scarf down gels and sports drinks while you run without upsetting your stomach? Practice, practice, practice, according to coaches and marathon veterans. That’s the idea that an Australian study published in the Scandinavian Journal of Science and Medicine in Sports recently put to the test.

First, they asked 18 trained runners to try a three-hour run while ingesting 90 g of carbohydrate per hour in gel form. Every single one of them reported GI symptoms, and two-thirds of them reported “severe” symptoms. Then half the runners did ten days of one-hour runs while ingesting 90 g of carbohydrate, while the others received placebo gels. When they repeated the three-hour run, the gut-training group had a 44-per cent reduction in gut discomfort, less carbohydrate malabsorption – and, crucially, a five per cent improvement in running performance. The placebo group, in contrast, was no better off than in their initial test.

The gut training protocol didn’t cure everyone’s problems. And, realistically, getting a full 90 g of carbohydrate per hour is probably more than most runners really need. But 60 g remains a good goal – and that’s still about twice as much as most marathoners manage to ingest in races. So if you want to make sure you’re ready to handle race-day nutrition, make sure to incorporate some dress rehearsals in training.