EE WAS OPENING THE DUMP GATES ON BOTTOM OF LOADED WASTE TRAILER. EXERTED EXCESSIVE FORCE WHEN PULLING LEVER TO OPEN THE GATE, & EE FEELS HE MIGHT HAVE PULLED OR STRAINED A MUSCLE. ***REPORT OR IGINALLY NOT COMPLETED OR FILED WITHIN THE REQUIRED TIME FRAME; BECAUSE THE EE DID NOT SEEK MEDICAL ATTENTION.**