We are comparing two pneumatic compression devices, VenaFlow (stationary) and MCS (portable) in both the supine an standing position. We will start supine and will take 3 baseline measurements of venous velocity and then apply a device and take 3 measurements of the increase in peak venous velocity. We will repeat this with the second device. We will then have the subject stand and repeat the above with each device. We will randomize the order of the devices in the supine and standing position. This study will involve 10 healthy subjects of various ages and 10 total hip replacements (THR) patients.