 MATERIALS AND METHODS IRB approval and informed consent was obtained from all subjects. Forty healthy subjects N 40 between the ages of 50 to 80 participated in the study. Half of the subjects N 20 were non-obese with a Body Mass Index BMI 30. The other half of the subjects N 20 were obese with a BMI 30. Exclusion criterion included a prior history of deep vein thrombosis or pulmonary embolism, or any trauma or surgery involving any part of the lower extremities. 