From reading Mantak Chia, he seems to place a great deal of importance on the tightness and strength of the anus as a pump to raise sexual energy up the spine at the point of orgasm. Also, he says this is a potential leakage point in the body for energy to escape. I am wondering if anal play, which causes the anus to relax and stretch will actually have negative effects on sexual practice. From what I have heard the penis should not be inserted to long. You should use good lubricate.