 Subjects will come to the Mayo Clinic 4 times. On Study Day 1 Subjects will be screened with a medical history physical and a 75 g oral glucose tolerance test to determine if they are eligible for the study. On Study Day 2, subjects will report to the clinic after an overnight fast, undergo a euglycemic clamp using deuterated glucose to determine insulin sensitivity, and in addition have a muscle biopsy basal biopsy for comparison. On Study Day 3, subjects will report to the clinic after an overnight fast, and undergo a Volume Oxygen Maximum VO_2 max determination. On Study Day 4, subjects will report to the clinic after an overnight fast to perform an exercise bout with muscle biopsy 30 minutes after the end of exercise. This will be followed by an overnight fast, and an additional muscle biopsy at 24 hours post exercise. 