Inclusion Criteria:1. Male 2 .18 - 55 years of age 3. Body mass index (BMI) lower or equal to 30 kg/m2 4. Absence of severe systemic disease that results in functional limitations (i.e. poorly controlled hypertension, angina pectoris, prior myocardial infarction, pulmonary disease that limits activity) 5.Subjects must be able to comprehend spoken and written English