on the specific musculature involved. Some say that it encompasses all the muscles between the knees and shoulders, while others feel that the core is limited to the muscles between the ribcage and pelvis. As you can see, determining the muscles of the core is a complicated process. I classify the core into inner and outer muscles. The outer core includes the larger muscles such as the rectus abdominis, internal and external obliques, erector spinae, gluteus maximus, latissimus dorsi, quadratus lumborum, and psoas (figures 5. 1 and 5.2). These muscles are primarily responsible for producing and resisting
movement. The inner core muscles, on the other hand, form a cylinder that contracts just before and during limb movement to protect the spine by providing intra-abdominal pressure. These inner core muscles consist primarily of the multifidus in the rear, the transversus abdominis in the front and on the sides, the diaphragm up top, and the pelvic floor muscles on the bottom (figures 5.3 and 5 .4) .