Injured was hanging ventilation tubing 8R section, 40' outby #10 break in #1 entry. He went outby the LOB to get a piece of tubing 20""x10' he bent over twisted left handed and jerk. Felt something pop and felt pain in lower back. He reported numbness in his back 20 min. later. He went to the hospital where he was treated for back pain. Therapy and medication.