In previous studies of the round shoulder posture, it is reported
that one of the causes of scapular change is shorthening of the pectoralis minor, which is attached to ribs 3, 4, and 5, which
results in a forward bending shoulder joint (forward shoulder
position)19), which is the cause of changes in position20).
During the resting period, shortening of the lengthening of
the pectoralis minor resulted in a minor increase in muscle
activity tension during elevation, and limited upward
rotation, posterior tipping, and external rotation of the normal
scapula21). Many methods for measurement of the length of
the pectoralis minor have been suggested13). Borstad and
his co-researchers used a tape measure to measure from the
sternal notch to the coracoids15).