This project proposes to develop a user-friendly personal monitor of physical activity which would provide feedback to the individual relevant for the natural activity levels supporting weight control or cardiac fitness. Weight control is a major health problem in the United States. Studies indicate that after weight loss a most important behavior change to support continued weight control is increasing physical activity; moreover, increasing exercise through natural, 'life- style' activities appears preferred for lasting changes. Similarily, higher levels of naturally occurring locomotive activity appear to produce significant cardiovascular benefits. The studies and clinical work on altering levels of naturally occurring activity suffer from lack of both reliable, easily ised direct measurement of activity and forms of information feedback helpful for shaping behavior change. This project proposes to substantially correct these problems. Phase I would: 1) modify existing software and hardware for the activity monitor now marketed by IMS, 2) assess appropriateness of movement threshold for the age and activities of interest, 3) determine approximate activity criteria for exercise levels and 4) establish feasibility- possible acceptance and use of activity monitoring with feedback for these purposes in the field. Phase II: would refine the hardware and software and conduct validation studies.