EE WAS LAYING ON HIS SIDE WHILE HOLDING A 1"" IMPACT WRENCH, TIGHTENING THE IDLER BOLTS ON A D10 DOZER. AFTERWARDS, WHEN FINISHED, HE WAS GETTING UP WHEN HE FELT PAIN IN THE LOWER BACK. HE WAS EXAMINED AND DIAGNOSED TO HAVE ACUTE SPASM OF THE LOWER LUMBAR SPINE.