The major muscles of the neck and back include: the erector spinae, multifidus, rectus abdominus, transversus abdominus, internal obliques, external obliques, splenius, and quadratus lumborum.
The quadratus lumborum (QL) is a common muscle that is often associated with lower back pain; correct stretching of the QL can help ease this pain.
The external oblique muscles are situated on either side of the abdomen, they aid in the twisting movement of the trunk and contract strongly when doing sit-ups.
The internal obliques are opposite to the external obliques and are responsible for movement on the side that they are situated; the right internus obliques twist to the right and the left internus obliques twist to the left.
The Transversus Abdominus is often abbreviated to TVA and is a very important core muscle that is vital to maintaining good posture. Activities such as Pilates and Yoga focus on the contraction of the TVA to strengthen it.
Rectus Abdominus is the most superficial of the abdominal muscles. It is this muscle that forms the six-pack shape!
The erector spinae (sometimes known as sacrospinalis) is a group of different muscles that include iliocostalis, longissimus, and spinalis; these run up the length of the back.