['To investigate sprint-training effects on muscle metabolism during exercise in subjects with (type 1 diabetic group) and without (control group) type 1 diabetes.', 'Eight subjects with type 1 diabetes and seven control subjects, matched for age, BMI, and maximum oxygen uptake (Vo(2peak)), undertook 7 weeks of sprint training. Pretraining, subjects cycled to exhaustion at 130% Vo(2peak). Posttraining subjects performed an identical test. Vastus lateralis biopsies at rest and immediately after exercise were assayed for metabolites, high-energy phosphates, and enzymes. Arterialized venous blood drawn at rest and after exercise was analyzed for lactate and [H(+)]. Respiratory measures were obtained on separate days during identical tests and during submaximal tests before and after training.', 'Pretraining, maximal resting activities of hexokinase, citrate synthase, and pyruvate dehydrogenase did not differ between groups. Muscle lactate accumulation with exercise was higher in type 1 diabetic than nondiabetic subjects and corresponded to indexes of glycemia (A1C, fasting plasma glucose); however, glycogenolytic and glycolytic rates were similar. Posttraining, at rest, hexokinase activity increased in type 1 diabetic subjects; in both groups, citrate synthase activity increased and pyruvate dehydrogenase activity decreased; during submaximal exercise, fat oxidation was higher; and during intense exercise, peak ventilation and carbon dioxide output, plasma lactate and [H(+)], muscle lactate, glycogenolytic and glycolytic rates, and ATP degradation were lower in both groups.'] Does sprint training increase muscle oxidative metabolism during high-intensity exercise in patients with type 1 diabetes?