The overall objective of this project is to gain further insight into the possible benefits of supplementation with glutamine (GLN), a natural dietary amino acid, enhancing insulin sensitivity in adolescents with T1D. To elucidate the impact of glutamine, the investigators will use a method called the 'euglycemic, hyperinsulinemic clamp': it consists of giving an IV drip of insulin, while the drop in blood sugar is prevented by giving variable, precisely measured amounts of glucose by vein: the amount of glucose required to prevent a drop in blood sugar reflects the body's sensitivity to insulin. The investigators will also give an IV drip of glucose and arginine (a building block of protein) 'tagged' with non-radioactive isotopes to better understand how glutamine may work. This procedure will be performed in 2 groups of 10 adolescents in the morning either after a strenuous exercise performed the previous afternoon (group 1; n=10), or after a sedentary day (group 2; n=10). Each subject will be studied twice, once after taking oral GLN, once after placebo, in separate clinical research center (CRC) admissions a few weeks apart, in random order.