Investigate the loads on the shoulders relative to a single strap satchel versus a dual strap satchel with a waist belt. Investigate the lower extremity and physiological demands of delivering mail with a cart versus a dual satchel in a return to work environment. Investigate how handling and reading mail affect the ability to recognize slip/trip/fall hazards on route as well as the severity of the type of slip. These studies utilized heart rate monitors, surface EMG, eye tracking, as well as tribology related measurements.