go on wikipedia and type ''muscles'' if know one knows the answer here, don'T post twice the same question...

Firstly, I assume that you are referring to the area below the neck and above the gluteal region. Also, some muscles are technically in the back but don't act on the back, notably some of the rotator cuff muscles around the scapula. So the number varies depending on how you define the back (for example, the deltoid is thought to cover the shoulder but its fibres reach onto the scapula in the back). I will include them for this answer, since technically they are in the back. You have: The superficial extrinsic back muscles of Trapezius Rhomboid major and minor Levator scapulae Latissimus dorsi The intermediate extrinsic back muscles of Serratus posterior superior Serratus posterior inferior (sometimes grouped together as serratus posterior) The superficial intrinsic back muscles of Splenius cervicis Splenius capitis The intermediate intrinsic back muscles of Iliocostalis Longissimus Spinalis These are sometimes collectively referred to as Erector Spinae The deep intrinsic back muscles get more complicated Transversospinalis is technically a group of muscles, made of the following: Semispinalis Multifidus Rotatores However, the semispinalis muscle can be further divided into three parts according to the superior parts of attachments as Semispinalis capitis Semispinalis thoracis Semispinalis cervicis The deep intrinsic layer of muscles continues with Interspinales Intertransversarii Levatores costarum, none of which are considered part of transversospinalis But some muscles are in the back but have effects elsewhere and so are considered muscles *OF* the back, even though they are muscles *IN* the back (some of them only partially). Supraspinatus Infraspinatus Teres minor Subscapularis (these are the rotator cuff muscles that are around the scapula in the back) Teres minor Deltoid Psoas major Quadratus lumborum So, since it depends on how you count them, and because these are paired (i.e. one on the left and another on the right) you could have up to 56 muscles in the back. More if I have missed any.

If you are prepared to count them, see the following website. Don't forget to double up for the other side of the body! http://www.innerbody.com/image/musbov.html