Exercise Intensity, Metabolic Rate and Insulin Sensitivity

The primary goal is to test the hypothesis 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. Secondary goals are 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.

A secondary study is designed to evaluate potential mechanism. Hypotheses are that changes in muscle lipid metabolism, mitochondrial function, fat and cellular insulin signals will be increased following the high intensity interval exercise. In addition, these changes will be related to changes in insulin sensitivity and increases in protein metabolism and muscle damage.

Inclusion Criteria:

• healthy premenopausal African-American or Caucasian women ages 19 - 42

Exclusion Criteria:

• subjects cannot be smoking,
• taking medications which alter energy expenditure or fuel utilization,
• be diabetic or have a body mass index (BMI) less than 18 or more than 35.
• Also subjects cannot be pregnant or have cardiopulmonary disease.