Some Olympic athletes are using a new tool they hope will boost their medal chances this summer: continuous glucose monitors.
The market for continuous glucose monitors (CGMs) is already worth billions of dollars per year. Manufacturers are eyeing further growth in the sport and wellness sector, where top athletes could be trend-setters.
Some top athletes and their support staff use CGMs to assess calorie intake and workout intensity. The benefit during races lasting less than about 3 hours is seen as limited.
Retired Australian swimmer and Olympic gold medalist Chelsea Hodges said CGMs helped her remedy bouts of extreme exhaustion during longer training sessions. Minute-by-minute monitoring showed she was prone to sagging blood glucose levels.
Dutch marathoner Abdi Nageeye won silver at the Tokyo Olympics. Seeking an "effortless run", Nageeye is using CGMs to improve sleeping and eating patterns so that he expends a minimum of energy during training.
Swedish steeplechaser Emil Blomberg, another Tokyo Olympian seeking to qualify for Paris, said he used CGMs to prevent overtraining. The devices also helped him work out that he needs to eat more during longer training sessions.
Cycling's world governing body UCI in 2021 banned the non-medical use of CGMs during races "to ensure the respect of individual qualities, the spirit of competition, and fairness" but other major sports have not followed suit.
Sports nutrition researchers say benefits have so far been anecdotal, with no clear evidence CGMs give a competitive edge.
Understanding how glucose tracking can inform an athlete's calorie intake and training schedule is still in its infancy.
Using up more energy in training than calories available from food, for example, can over time compromise bone strength, the immune system and fertility. However, it has not yet been fully established how CGMs can help avoid that.
Among some surprise research findings, elite marathoners have remarkably high blood glucose levels during races, likely boosted by stress hormones. Many endurance athletes have extremely low glucose levels during pre-dawn sleep but it's not clear whether that is detrimental.
Researchers report most of their CGM advisory work for athletes without diabetes is for now based on anecdotal observations rather than validated findings.
