This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The specific aim of this project is to determine whether in children/adolescents with Type 1 Diabetes, the adaptive glucoregulatory response to exercise is attenuated, contributing to the high incidence of hypoglycemia occurring in this group of patients. In the management of patients with Type 1 diabetes mellitus (T1DM), hypoglycemia is a major clinical problem. Hypoglycemia may disrupt daily activities, cause life-threatening events, induce fetal damage, alter cognitive function in children, and exert long-term negative effects on intellectual function. Hypoglycemia often occurs in association with physical exercise, often forcing patients to renounce several beneficial effects of exercise, including improved insulin sensitivity and glycemic control, and improved control of blood pressure and prevention of cardiovascular disease, for which these patients are at elevated risk.