Employee was dumping 50lb bags of salt on the surface, in the A Frame. He stated he twisted wrong and pulled a muscle in his back. He was taken to the doctor on 3/26/2009. Doctor placed him on restricted duty. He had a follow-up appointment with the doctor on 4/8/09. The doctor returned him to full duty as of 4/09/09. Employee reported the injury on 3/26/2009.