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Going for gold

14th July 2021

People with type 1 diabetes have been pushing the boundaries of sporting excellence for the past 100 years. Now, thanks to technology like continuous glucose monitoring (CGM) and closed-loop, they are achieving more than ever before

Several athletes with type 1 diabetes are aiming for a medal at this summer’s Tokyo Olympics, while professional cyclists with Team Novo Nordisk continue to ride high. But how do they overcome the challenges to glycaemic control that sport and exercise pose in type 1? At this year’s Advanced Technologies and Treatment for Diabetes meeting, Dr Mike Riddell of the Muscle Health Research Centre, York University, Toronto, discussed how technology helps athletes with type 1 diabetes exercise safely and achieve sporting success.  

“Glycaemic control in sport is a major challenge, but CGM has taught us a lot and our research group is focused on how it can help support athletes. And there’ll be future advances in technology which will put more people on the podium,” he said.  

In 1926, the British physician RD Lawrence, who had type 1, discovered that aerobic exercise – tennis or rowing – made his insulin work much more effectively which, of course, can lead to hypoglycaemia. While this makes some fear exercise, and miss out on all its well-established benefits, others have taken on the challenge. Mike – who lives with type 1 himself and is a keen cyclist – cited examples including baseball player Bobby Clarke, who blazed the trail in the 1970s, long before CGM, and Olympic swimmer Gary Hall.

Technology makes it all possible

CGM, closed-loop, better insulins and glucagon have all helped make sport and exercise safer and pushed athletes to higher performance levels, by addressing the great glucose variability that exercise can bring. “We’re starting to understand the relationship between time in range and performance and we are now testing several closed-loop systems in exercise mode to see if we can protect athletes from hypo- or hyperglycaemia in sporting competition,” Mike explained. “We’re also starting to incorporate some other wearables, including heart rate and sleep monitors, to see if we can better understand the physiologic demands athletes placing on themselves. We have ambitious goals for athletes with type 1 diabetes.”     

Team Novo Nordisk cyclist Sam Scott then took to the stage to talk about the day-to-day reality of pursuing his sport. CGM and cycling monitors can be used remotely to investigate non-invasively some of the challenges during elite-level cycling and retrospectively analyse the data and highlight challenges with the team doctor. This approach was used in the team’s 2019 tour of California, where seven male athletes with type 1 diabetes raced for three to six hours per day, covering a distance of 126 to 218 km with a total elevation almost 21 km – all at a top speed 50 km/h. Then there’s the logistics. “When you come on one of these tours you realise it’s kind of like a moving circus. Finish your race, back to the van, get to the next hotel, recover and get ready for next race! It’s more difficult than waking up in your own bed and doing these races.”

Team Novo Nordisk has been very successful in competing against teams without diabetes. One rider was awarded the ‘most courageous rider’ jersey, and there were Top 20 and Top 10 results, and three breakaways, over the course of the California tour. When they looked back at the CGM data, they were really pleased to see how well riders kept within target during rides and, during the seven days, there were almost no hypos. There was just one concerning issue – overnight there was a steady increase in below-target glucose for all the cyclists. “The use of CGM has really highlighted to us that we need to work on this post-exercise period to help recovery and, for safety, to avoid these night-time hypos,” Sam said.

So, CGM has been really important in working with these athletes. There are so many advantages associated with being able to see their data in real time and make short-term decisions, and going through data afterwards to learn and adjust strategies for future races and training. For instance, it helps adjust carbohydrate intake and monitor insulin needs. Meanwhile, CGM alarms are particularly useful, especially overnight for avoiding hypos.

The one drawback is the sensor time lag, which does become apparent during exercise at such high speeds and when prompt decisions about refuelling might be needed. Mike commented that this might be solved by developing different predictive algorithms built into CGMs, for when glucose might be rising or dropping during a sporting performance.

Meanwhile, from the medical side, Dr Federico Fontana, Head of Performance at Team Novo Nordisk, has been making use of all the different data streams coming from his cyclists. “We are trying to better merge training data with glucose data into a common display,” he explained. This, hopefully, will lead to better training, glucose management and control, and the ability to spot patterns and trends. They’ll be able to check out differences between race days, recovery days or training at home, using very simple displays. “The long- term aim is to develop some personalised approaches through a dashboard that can support the athlete with their personal decision-making, with the whole team supporting them in turn.”

So, after 100 years of athletes trying to compete on insulin, there have been some impressive achievements – and more to come.  “We know that some recent developments like closed-loop systems, digital pens, CGM and intermittently scanned glucose monitors have really shed light on the accomplishments of some of these athletes and their level of glycaemic control. The technology allows them to make critical on-the-minute decisions about nutrition, hydration or insulin therapy patterns and we think that emerging systems may help to further improve Time in Range in these athletes,” Mike said. “And, finally, from Team Novo Nordisk, we think that novel ways of displaying data to the athletes and the coaches might give a better glimpse on how to optimise performance in these incredible human beings.”

Recommended reading
Much of this new knowledge has been highlighted in a recent position statement on CGM and intermittent glucose monitoring by EASD/ISPAD, and endorsed by the American Diabetes Association (published in both Diabetologia and Paediatric Diabetes). This highly recommended reading sets out detailed information on when it is safe to exercise, how different types of exercise produce different glucose responses, and sets out glucose targets based on this. Access the position statement on the EASD website.

For more on this topic, see Professor Mike Riddell’s presentation in our Insulin@100 series, ‘Exercise and insulin: a potent synergy’.

You can also hear Mike in conversation with fellow cycling enthusiast Professor Miles Fisher in their contribution to our ‘The long and short of it’ series, ‘This sporting life’.

The views expressed in this article are those of the author, Dr Eleanor D Kennedy.