More and more people with type 1 diabetes are active and there are now a number of individuals living with type 1 diabetes competing at the highest level in their chosen sport. There are clearly benefits of exercise, but also challenges.
How common is Type 1 Diabetes?
According to the International Diabetes Federation, approximately 463 million people are currently living with diabetes worldwide, and this number is projected to reach 578 million by 2030 (1). There are several types of diabetes with the two main classes being type 1 diabetes and type 2 diabetes. Type 2 diabetes accounts for about 90% of cases worldwide, of which 50% are treated by drugs with an associated risk for hypoglycaemia (mainly insulin). Type 1 diabetes is the most common endocrine condition in children and young adults (2), with an estimated 40 million individuals living with the condition worldwide (1).
Type 1 diabetes and exercise
Regular exercise is accepted as a cornerstone for type 1 diabetes management and maintenance of overall health. However, exercise can also represent a considerable challenge for the athlete living with type 1 diabetes as it increases the risk of potentially life-threatening hypoglycaemia or hyperglycaemia with ketoacidosis. An understanding of glucose targets for safe and effective exercise and the hormonal responses to different forms of exercise is important. A person living with type 1 diabetes has to carefully balance their insulin dose with carbohydrates they eat/drink and the amount of exercise, as well as taking other factors into consideration that can affect their blood glucose concentration.
Regular exercise is accepted as a cornerstone for type 1 diabetes management and maintenance of overall health.
Effect of exercise on blood glucose in type 1 diabetes
Exercise can potentially lower or raise blood glucose (4). During exercise, blood glucose can lower due to the muscles using glucose as energy and the body can become more sensitive to insulin. However, sometimes blood glucose concentration increases due to other factors, for example, the effect of other hormones such as adrenaline that are also released during physical activity (5).
Everyone’s diabetes is different, and individuals react differently to exercise. It is important that people with diabetes understand how their blood glucose responds to exercise so they can manage these fluctuations and prevent hypoglycaemia or hyperglycaemia. Exercise must always be prepared for in advance, and insulin or food adjustments might be needed in order to stay within the optimal blood glucose range (4).
Blood glucose trends caused by different types of exercise in individuals living with type 1 diabetes. In general, low to moderate intensity exercise (e.g. jogging or low intensity cycling) decreases blood glucose levels, high intensity exercise increases blood glucose level, and mixed activities are associated with glucose stability. However, this is not always the case. Individual responses are dependent on various additional factors, including the duration and intensity of the activity; initial blood glucose concentrations; individual fitness level; concentrations of insulin, glucagon, and other hormones in the circulation; and the nutritional status of the individual.
Competing as an athlete while living with Type 1 diabetes
Many sports teams now employ sport scientists and researchers to assist with the nutrition and training practices of their athletes, but rarely in combination with a condition such as type 1 diabetes. An example of a team that are placing a major focus on research, not only to improve athlete performance but to gain insight into endurance sport and type 1 diabetes are Team Novo Nordisk (TNN). TNN is a global all-diabetes sports team, spearheaded by the world’s first all-diabetes professional cycling team. The men’s professional cycling team races on the International Cycling Union (UCI) Professional Continental tour, competing in major professional races around the world. The team’s mission is to inspire, educate and empower people affected by diabetes, by showing what may be possible while living with diabetes.
The TNN athletes provide a completely unique situation due to the challenging medical condition that is type 1 diabetes, which has the potential to impact almost every aspect of their lives. Professional road cycling is perhaps the ultimate setting to combine sport science and endocrinology research into one of the most physically demanding sports; combining extremes of exercise duration, intensity and frequency (6). Road cycling involves high training volume, long seasons with frequent competition days (60-100 per year), with races up to 6-8 hours and stage races ranging from 5 days to 3 weeks (6). Professional riders are required to regularly compete alongside multiple uncontrollable variables such as changing weather and road conditions, variable team tactics and different altitudes. This is compounded by tight race schedules, travel distances between race days, with frequent domestic and international flights. An individual with type 1 diabetes wishing to compete in professional road cycling competitions has the monumental task of managing their blood glucose alongside challenges of the training and races.
In order to make an impact and implement change, the coaches, researchers and medical staff working with the TNN athletes need to develop their trust build a strong relationships that will allow a continuously share of knowledge and expertise.
Recent developments in diabetes technology (16) allow us to collect a lot of data from the riders non-invasively. For example, the researchers working with TNN have access to 24 hour continuous glucose monitoring data, insulin dosing using smart insulin pens or insulin pumps, and increasingly effective means to collect nutrition data both in ride and throughout the rest of the day.
Recent developments in diabetes technology allow us to collect a lot of data from the riders non-invasively.
In addition, the team have all of the performance metrics from the head units on their bikes including heart rate, power, distance covered, speed, elevation and temperature. It is hoped that this information will provide insight into how these athletes can improve their training and competition while also being transferable to other athletes, both with and without diabetes.
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Colberg SR, Sigal RJ, Yardley JE, et al. Physical Activity/Exercise and Diabetes: A Position Statement of the American Diabetes Association. Diabetes Care 2016;39(11):2065-79.
Riddell MC, Gallen IW, Smart CE, et al. Exercise management in type 1 diabetes: a consensus statement. The lancet Diabetes & endocrinology 2017;5(5):377-90.
O'Reilly M, O'Sullivan EP, Davenport C, et al. "Dead in bed": a tragic complication of type 1 diabetes mellitus. Irish journal of medical science 2010;179(4):585-7.
Lucia A, Hoyos J, Chicharro JL. Physiology of professional road cycling. Sports medicine (Auckland, NZ) 2001;31:325-337
Riddell MC, Pooni R, Fontana FY, Scott SN. Diabetes Technology and Exercise. Endocrinology and metabolism clinics of North America 2020;49:109-125
Other related reading:
McCarthy O, Eckstein ML, Scott SN, et al. Glycemic responses to strenuous training in male professional cyclists with type 1 diabetes: a prospective observational study. BMJ open diabetes research & care 2020;8(1).
Scott SN, Christiansen MP, Fontana FY, et al. Evaluation of Factors Related to Glycemic Management in Professional Cyclists With Type 1 Diabetes Over a 7-Day Stage Race. Diabetes Care 2020;43(5):1142-45.
Hegele RA, Maltman GM. Insulin's centenary: the birth of an idea. The lancet Diabetes & endocrinology 2020;
Riddell MC, Scott SN, Fournier PA, Colberg SR, Gallen IW, Moser O, Stettler C, Yardley JE, Zaharieva DP, Adolfsson P, Bracken RM. The competitive athlete with type 1 diabetes. Diabetologia 2020;
Gawrecki A, Zozulinska-Ziolkiewicz D, Matejko B, Hohendorff J, Malecki MT, Klupa T. Safe Completion of a Trail Running Ultramarathon by Four Men with Type 1 Diabetes. Diabetes technology & therapeutics 2018;20:147-152
Belli T, de Macedo DV, Scariot PPM, de Araujo GG, Dos Reis IGM, Lazarim FL, Nunes LAS, Brenzikofer R, Gobatto CA. Glycemic Control and Muscle Damage in 3 Athletes With Type 1 Diabetes During a Successful Performance in a Relay Ultramarathon: A Case Report. Wilderness & environmental medicine 2017;28:239-245
Sane T, Helve E, Pelkonen R, Koivisto VA. The adjustment of diet and insulin dose during long-term endurance exercise in type 1 (insulin-dependent) diabetic men. Diabetologia 1988;31:35-40
van Dijk JW, Eijsvogels TM, Nyakayiru J, Schreuder TH, Hopman MT, Thijssen DH, van Loon LJ. Glycemic control during consecutive days with prolonged walking exercise in individuals with type 1 diabetes mellitus. Diabetes research and clinical practice 2016;117:74-81
Lespagnol E, Bocock O, Heyman J, Gamelin FX, Berthoin S, Pereira B, Boissière J, Duclos M, Heyman E. In Amateur Athletes With Type 1 Diabetes, a 9-Day Period of Cycling at Moderate-to-Vigorous Intensity Unexpectedly Increased the Time Spent in a State of Hyperglycemia, Which Was Associated With Impairment in Heart Rate Variability. Diabetes Care 2020;
Mattsson S, Jendle J, Adolfsson P. Carbohydrate Loading Followed by High Carbohydrate Intake During Prolonged Physical Exercise and Its Impact on Glucose Control in Individuals With Diabetes Type 1-An Exploratory Study. Frontiers in endocrinology 2019;10:571
Adolfsson P, Mattsson S, Jendle J. Evaluation of glucose control when a new strategy of increased carbohydrate supply is implemented during prolonged physical exercise in type 1 diabetes. European journal of applied physiology 2015;115:2599-2607
Nine Athletes with Type 1 Diabetes [article online], 2019. Accessed 07.12.2020 2020