EMPLOYEE WAS DRIVING A DUMP TRUCK WORKING UNDER CRUSHER HAULING 1"" STONE. THE TRUCK INVOLVED HAS A DUMP BODY WITH A TAILGATE WHICH IS RELEASED BY A PULL HANDLE LOCATED ON THE FRONT OF THE BODY BY THE DRIVER'S DOOR. SHE OPENED THE DOOR, REACHED OUT WITH LEFT HAND TO PULL HANDLE TO RELEASE GATE TO DUMP LOAD, STRAINING HER LEFT SIDE AND BACK.