Employee was pulling new 350 MCM cables from the power car to the new camp. He stood up from a crouching position and felt a belt of pain go across his lower back, above his tail bone. He went to the PA's at 11pm who gave him med's for the pain and sent him to the medical clinic at 930am on 5/11/05. He was given a 7 day light duty release, ""no lifting or pulling"".