PERSON WORKED ALL DAY ON 34 BUTT BELT DRIVE ALIGNING POWER PACK. EE DID NOT REPORT ANY TYPE OF INJURY THAT DAY. THE PAIN BECAME ACUTE ON SATURDAY EVENING & SUNDAY. ON MORNING OF 8/16/04, EE CALLED IN TO WORK & REPORTED INJURY TO SUPERVISOR. EE WENT TO THE DR. ON 8/16/04.