 The Primary Objective of this study is to develop and validate the algorithm needed to detect upright posture with a waist 3-axis accelerometer. A Secondary Objective is to determine the performance reliability of posture detection of the thigh and waist accelerometers when exposed to activities of daily living standing, walking, climbing stairs. We will test the primary and secondary objectives in normal subjects using a single study design. Studies for both objectives will be conducted simultaneously on each subject on a single study day. Normal subjects will wear a device with the waist accelerometer incorporated within the controller box. 