 The major muscles of the core reside in the area of the belly and the mid and lower back (not the shoulders), and peripherally include the hips, the shoulders and the neck.Major muscles included are the pelvic floor muscles, transversus abdominis, multifidus, internal and external obliques, rectus abdominis, erector spinae (sacrospinalis) especially the longissimus thoracis, and the diaphragm.The lumbar muscles, quadratus Lumborum (deep portion), deep rotators, as well as cervical muscles, rectus capitus anterior and lateralis, longus coli may also be considered members of the core group.