EE WAS ASSIGNED TO REMOVE & REPLACE THE DUMP DOOR ARM ON TLR0621. WEIGHT APPROX 35-40 PDS. EE HAD FINISHED THE JOB & WAS CARRYING THE DOOR ARM THAT WAS REMOVED BACK TO TLR0623 WHICH WAS ON TH E SOUTH SIDE OF THE SHOP. EE STEPPED OFF THE CEMENT APRON TO THE GROUND & FELT A HOT TINGLE IN HIS OWER BACK. EE WAS SEEN BY CHIROPRACTOR ON THEFOLLOWING DATES: 12/11, 12/18 & 12/29/00