EE WAS A MEMBER OF MAINTENANCE CREW, PERFORMING PREVENTIVE MAINTENANCE ON A PRODUCTION HAUL TRUCK. THE EE'S JOB WAS TO REMOVE MUD FROM THE UNDERSIDE OF TRUCK, WITH HIGH PRESSURE WATER HOSE. EE WAS CARRYING OUT HIS NORMAL DUTIES; WHEN HE EXITED, FROM UNDER TRUCK, HE NOTICED HIS LOWER BACK WAS IN PAIN. HE HAD TWISTED HIS LOWER BACK.