Psoas is the deepest core muscle situated one on each side of the body. These muscles called psoas  major are the ones that attaches upper body to lower body. These muscles connects spine to legs. Psoas (psoai-plu) muscle are important in all terms – energetically, physically, and emotionally. Any stress that we experience can cause pain in posas muscle and hurts back. Yogis often detoxify these muscles to keep system calm.