In this exercise we are finding movement in the pelvis and activating the hamstrings without a lot of deep glute squeezing or clenching. We use a block between the knees to help keep from that clenching sensation. So we are moving from a posterior tip to an anterior tip without getting a lot of upper spine movement AND while keeping the hamstrings activated while pulling the feet up the wall. If you don't get this one, ask me. I am happy to walk you through it.