Could you tell me what are core muscles and how do you exercise them?

Muscles of abdomen &: Abdominal muscles and those of the lower back. Strengthening these will protect your back, keep your middle from protruding, and are an essential part of exercise. There are too many forms to enumerate. But the simplest exercise is bent knee situps, where you can cross over to alternate knees to get you obliques!

See below: 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. Minor core muscles include the latissimus dorsi, gluteus maximus, and trapezius. A great introductory core program can be found at www.therehabzone.com