Three-way, Cross-over Closed-loop Exercise Study

Blood glucose control systems that utilize both insulin and glucagon to manage blood sugar are paving the way to revolutionize the management of this disease. The benefit of improved control of blood sugar levels compared to standard insulin pump therapy has already been demonstrated. However, the risk of low blood sugar in type 1 diabetes increases considerably during exercise. The investigators research group has shown that small doses of glucagon can prevent low blood sugar when used in a blood sugar control system in patients with type 1 diabetes. However, as insulin sensitivity changes occur very rapidly during exercise, the ability to recognize the onset of physical activity in order to appropriately adjust the insulin and glucagon delivery is vital to helping prevent exercise-induced hypoglycemia. The purpose of this study is to test how well a new modified blood sugar control system controls blood sugar during exercise compared to: 1) the current system without modifications and 2) standard insulin pump therapy.