15 minute core training workout you can print or share.The core muscles include  Major muscles included are the pelvic floor muscles, transverses abdominis, multifidus, internal and external oblique, rectus abdominis,erector spinae (sacrospinalis) especially the longissimus thoracis, and the diaphragm. Minor core muscles include the latissimus dorsi, gluteus maximus, and trapezius.