The "ups" and "downs" of a bike race in people with type 1 diabetes: dramatic differences in strategies and blood glucose responses in the Paris-to-Ancaster Spring Classic

Can J Diabetes. 2015 Apr;39(2):105-10. doi: 10.1016/j.jcjd.2014.09.003. Epub 2014 Dec 6.


Objective: Recommendations for insulin adjustments and carbohydrate intake exist for individuals with type 1 diabetes who are undertaking moderate exercise. Very few guidelines exist for athletes with type 1 diabetes who are competing in events of higher intensity or longer duration. This observational study reports the strategies adopted by 6 habitually active men with type 1 diabetes (glycated hemoglobin = 8.3%±2.0%) undertaking a relatively intense endurance cycling event.

Methods: Participants wore continuous glucose monitoring (CGM) sensors for 24 hours before competition, while racing and overnight postrace. They were asked to eat their regular meals and snacks and make their usual insulin adjustments before, during and after competition. All food intake and insulin adjustments were recorded in detail.

Results: Participants used a variety of adjustments for exercise. Of 6 participants, 4 decreased their insulin dosages and all participants consumed carbohydrates during the race (mean = 87±57 g). In spite of these strategies, 3 of the 6 participants experienced mild to moderate hypoglycemia (not requiring assistance) during the event. Hyperglycemia was seen in all participants 3 hours postexercise. There were no incidents of nocturnal hypoglycemia.

Conclusions: Individuals with type 1 diabetes can compete in intensive long-distance athletic events using a variety of nutrition- and insulin-adjustment strategies. In addition to finely tuned insulin adjustments and increased carbohydrate intake, vigilance will always be required to maintain some semblance of glycemic control during events of extended duration.

Keywords: ajustement de l'insuline; blood glucose control; diabetes; diabète; hypoglycemia; hypoglycémie; insulin adjustment; régulation de la glycémie.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Bicycling / physiology*
  • Blood Glucose / analysis
  • Blood Glucose / physiology*
  • Diabetes Mellitus, Type 1 / blood
  • Diabetes Mellitus, Type 1 / epidemiology*
  • Diabetes Mellitus, Type 1 / metabolism*
  • Diabetes Mellitus, Type 1 / physiopathology
  • Humans
  • Hypoglycemia / blood
  • Hypoglycemia / diagnosis
  • Hypoglycemia / drug therapy
  • Insulin / administration & dosage
  • Insulin / therapeutic use
  • Male
  • Middle Aged
  • Monitoring, Ambulatory
  • Ontario
  • Young Adult


  • Blood Glucose
  • Insulin