Significance: This study addresses questions of clinical and scientific importance. It will help clarify the benefits and risks of aerobic and resistance exercise training in people with type 1 diabetes. Depending on the strength of any differences found, the study will either stand alone or provide pilot data that will set the stage for a larger definitive study. Even if results are substantially different from our expectations, this study will provide valuable new information on the effects of different exercise modalities on metabolic control, body composition, cardiovascular risk factors, and quality of life in this high-risk population.