INJURED EE WAS LIFTING A ROCK DUSTER FROM THE BACK OF A ROOF BOLTER. INJURED HAD LIFTED THE ROCK DUSTER WITH A COME-A-LONG. INJURED PUSHED THE ROCK DUST AROUND. WHEN HE DID THIS HE FELT A PAIN IN HIS LOWER BACK. (INJURED DID NOT REQUEST MEDICAL TREATMENT UNTIL 5/19/03).