During low- to medium-intensity exercise, most of the energy you use is sourced from fats. Most club cyclists will carry about 10 per cent body fat and, as 500 g of fat stores just under 4000 calories, there is little to worry about. However, when the going gets tough, it’s a different story. Muscles balance your sugar intake you can ‘cheat’ the system.

A 2:1 glucose/fructose ratio can increase the absorption rate, with many duel-fuel drinks and gels providing a 1:0.8 ratio that, they claim, enables riders to increase their sugar absorption rate to 90 g an hour or more. Once, elite riders were assumed to have the same 60–70g rate as mere mortals, but modern science continues to make advances. Around five years ago, a rate of 1g of carbohydrate per kg of bodyweight per hour (around 75 g for elite riders) was seen as viable. Chris Froome’s legendary stage 19 victory in the 2018 Giro d’Italia with a solo break over the Colle delle Finestre saw him averaging around 100 g an hour throughout the five-hour stage. Since then, some pro riders have achieved levels of 120 g an hour.

The change has come through a combination of scientific advances in gels and fuel drinks, and a focus on training the gut by gradually increasing the carb intake over the course of pre-season training. Endurance athletes are especially prone to Gastrointestinal (GI) problems and can suffer anything from constipation and bloating through to diarrhoea and vomiting. It’s not a pleasant subject for a recipe book, but, hey, if it’s going to feature anywhere it’s in a book called On the Go. Anyone who remembers Tom Dumoulin losing two minutes when stomach cramps forced him to stop and defecate by the side of the road after climbing the Stelvio on stage 16 of the 2017 Giro d’Italia, will understand how devastating and costly, not to mention embarrassing, GI issues can be.

The main problem athletes face is how long it takes for the food and drink they’ve consumed to pass from the stomach to the intestine. This is called the gastric emptying rate. Unless the stomach empties, no absorption of sugars can take place, and this rate may be affected by stress, which can be driven by adrenaline and nerves, and the body may go into fight or flight mode. It is also a natural reaction to the body undergoing high-intensity activity. In addition, during strenuous exercise, the demand for blood from the muscles and the skin takes priority, and the subsequent reduction in blood flowing to the stomach limits its ability to function fully.

Easing up on the pedals is not an option, but there are steps you can take to alleviate the issues, with ensuring you’re hydrated at all times being the most important. How well the stomach and the intestine function depends on and is eased by, the presence of liquid. Other measures you should take are ensuring you keep as cool as possible, avoiding foods with a high-calorie density (having a lot of calories in a small quantity of food) or those that are very high in fibre, and eating regular, bite-sized portions.

- Alan Murchison