Enrolled subjects will arrive at 3pm the day before measurement day at the CRC. Measurement of Muscle Mass and Volume with DEXA (Night before). Muscle mass will be determined using a DEXA scan (GE Lunar iDXA). The patient will be placed supine on the table and a whole body DEXA performed. The procedure takes ~15 minutes and radiation exposure is comparable to the dose received in a 2-hour airplane flight (~0.04 mrem). The same CRC operator will perform all DEXA analyses. The body will be divided in subregions: Truncal area, android, gynoid, right and left arm, and right and left leg. The investigators will be able to measure lean and fat mass individually for each subregion. The investigators will also analyze specific regions of interest for lean body mass, including the thigh and calf. The coefficient of variation for repeated measures of lean tissue is <1%.