Study on elite athletes with Type 1 diabetes provides new insight on importance of monitoring glucose levels during exercise and overnight


Results show 24-hour monitoring of glucose levels during and after exercise is key for safety

TORONTO, Monday, March 16, 2020 – Tracking glucose levels over 24 hours can help athletes with Type 1 diabetes monitor glycemic control and better manage hypoglycemia overnight, new research from York University has found.

Professor Michael Riddell in York University’s Faculty of Health and Sam Scott, a postdoctoral researcher in Riddell’s lab when the study was done, and now working at the University of Bern in Switzerland, along with other colleagues in the U.S. and Europe, investigated the glycemic control and performance metrics of professional cyclists over a seven-day Union Cycliste Internationale World Tour stage race (the Tour of California).

The researchers say the results provide a unique insight into current practices of elite athletes living with Type 1 diabetes and new evidence of the habitual eating and insulin dosing patterns of professional athletes during multi-stage endurance events.

Athletes with Type 1 diabetes have considerable challenges when managing their blood glucose, particularly around training and competition. In this study, published today in Diabetes Care, six male professional cyclists with Type 1 diabetes were observed during the Tour of California. During the race the athletes cycled between three and seven hours and covered 128 to 219 km on each of the seven days of the competition. They used sensor technology to monitor their glucose levels and keep it under control during the race. Over the entire race, the riders used smart insulin pens to automatically record insulin dosing and timing.

“These cyclists are riding five hours a day for seven days in a row. You could not do this 20 years ago,” says Riddell. “For athletes who compete in elite level sports on the world stage, managing their diabetes is critical to their performance. We’ve never known the severity of low blood sugar in elite athletes until now, but now they can identify this problem and they can fix it. For people living with diabetes, knowing your glucose levels in real time during and after any exercise event is extremely helpful and increases safety.”

The riders, from Team Novo Nordisk (TNN), where Scott is also now Head of Research, spent a high proportion of time in target glycemic range (3.9-10.0 mmol/L) during cycling, with little time in hypoglycemia (<3.9 mmol/L) over the seven days. In-ride carbohydrate intake (76 ± 23 g∙h-1) in these professional cyclists were in line with contemporary nutrition guidelines for athletes without diabetes. Average performance and diabetes-related metrics were compared with statistical analyses between racing days. In-ride nutrition consisted primarily of energy gels, high-carbohydrate energy bars, rice cakes, and bananas. Fluids consisted of water, a low- carbohydrate sports drink containing electrolytes, or cola.

During exercise, muscles can take up glucose without the need of the hormone insulin, therefore, these athletes need to adjust their insulin accordingly during training and races. Furthermore, as with all the other athletes that they are competing against, their peers without Type 1 diabetes, they need to be taking in enough fuel to meet their energy demands. Despite their high rates of performance, riders experienced a greater amount of time in hypoglycemia during the overnight recovery periods over the course of the tour, according to the study’s results.

Scott says these observations highlight the many glycemic challenges faced by professional athletes with Type 1 diabetes over a World Tour stage race.

“It’s important for us to note that although the riders performed well and generally had excellent in-ride glycemia, there was a tendency to struggle with nighttime hypoglycemia,” says Scott. “The risk of nocturnal hypoglycemia is something we are aiming to help with in the future.”

The results provide insight for those with Type 1 diabetes who do exercise and shows why they need to be aware of their blood sugar overnight, adds Riddell.

The researchers say the data will inform future research on strategies for people living with Type 1 diabetes to better manage their glucose during exercise. In addition, the comprehensive range of technologies used in this study, such as continuous glucose monitoring and connected insulin pens during a dynamic and challenging event, demonstrate what is possible and this will help researchers better understand factors that can influence glycemia around exercise.

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Media Contact: Vanessa Thompson, York University Media Relations, 647-654-9452,