The Non-Biopsy group will complete a VO2 maximum test, are provided food 2 days prior to assessments, exercise in the metabolic chamber, have a Resting Energy Expenditure test, complete a DEXA and have blood drawn. This group will stay overnight in the metabolic chamber and have the clamp procedure. Exercise training is exactly the same for both groups.

Those who select the Non-Biopsy group, in lieu of the biopsy test, will complete an Activities of Daily Living (ADL) test that involves sub-maximal VO2 assessment. The participants will also be asked to where an accelerometer home for 4 consecutive days after the ADL test.

The Biopsy group will also complete a VO2 maximum test, are provided food 2 days prior to assessments, exercise in the metabolic chamber, have a Resting Energy Expenditure test, complete a DEXA and have blood drawn. As with the Non-Biopsy group, this group will stay overnight in the metabolic chamber and have the clamp procedure. Exercise training is exactly the same for both groups. One week following the overnight metabolic chamber visit, participants in this group will undergo a muscle biopsy. This group will not complete the Activities of Daily Living (ADL) test nor will they be asked to wear an accelerometer.

Exercise training will consist of bicycle ergometer riding starting at 67% of heart rate max for 20 minutes. Exercise Intensity will be progressively increased every week until 80% of heart rate max for 40 minute sessions is reached.

To test the hypothesis that high interval exercise increases energy expenditure and Insulin sensitivity more than 2 days of rest or moderate intensity exercise cumulatively over 23 hours during and following the exercise

To evaluate exercise difficulty during moderate intensity exercise and high interval exercise as well as difficulty of activities of daily living and free living physical activity following rest, moderate intensity exercise and high interval exercise