MINER WAS PREPARING TO SERVICE HIS UNDERCUTTER. HE REMOVED HIMSELF FROM HIS CAB AND WALKED ABOUT 5 STEPS BEHIND HIS CUTTER. HE STEPPED ON A ROCK, THIS CAUSED HIM TO LOSE HIS BALANCE. HE TRIED TO CATCH HIMSELF WITH HIS LEFT ARM. THE WEIGHT OF HIS BODY CAUSED A STRAIN ON HIS LEFT SHOULDER.