“Our riders are a special group because they are used to consuming large amounts of carbohydrates during training. We suspect that some of them may therefore be able to go beyond 120 grams per hour. What we are already seeing in our results is that there are individual differences,”
said Kobe Vermeire, a postdoctoral researcher at UGent and a coach with Lotto-Intermarché.
A three-hour test using carbon isotopes
The research involves a cycling test lasting approximately three hours, during which a rider consumes a carbohydrate-rich drink providing around 140 grams per hour. Researchers add special isotopes to the drink, using variants of carbon atoms as markers to track what happens to the ingested carbohydrates inside the body.
During exercise, some of the consumed carbohydrates are used to provide energy. By collecting the rider's exhaled air and measuring the amount of isotopes it contains, researchers can estimate how much of the ingested fuel has actually been oxidized - the process through which the body uses it for energy.
“During exercise, the rider uses the carbohydrates, and the isotopes enter the body as well. We then collect the rider's exhaled air, which contains these isotopes,” Vermeire explained.
“Based on their quantity and the rate at which they are exhaled, we can calculate how much of the ingested carbohydrates the rider effectively uses,” added Jan Boone, a professor of exercise physiology and sports nutrition.
Potential gains in the closing stages of races
The practical implications could be significant if the research enables riders to maintain a higher rate of carbohydrate use over prolonged periods. During a long race, the body relies heavily on carbohydrate availability to sustain high-intensity efforts. As its readily available stores decline, the contribution from fat metabolism increases, which can make it harder to maintain the same level of performance.
“If we can increase the amount of carbohydrates a rider can absorb and use, they may be able to maintain their performance level for longer, including during the final hour of a race,” Boone said. “In stage races, this could also have an impact on recovery ahead of the following day.”
That possibility is particularly relevant in Grand Tours, where riders must repeatedly produce high levels of effort over several consecutive days. Better fueling during one stage could help preserve performance late in the race, while an improved nutritional strategy might also support preparation for the following day's efforts.
However, the research does not mean every rider should immediately increase their intake beyond 120 grams per hour. “It is important to measure individually how much each rider can handle. If someone consumes more carbohydrates than they can effectively process, this can cause gastrointestinal discomfort. That is why we want to tailor the nutrition strategy to each rider's individual capacity,” Vermeire concluded.