quadratus lumbarum
A muscle that is tensed and contracted is hypertonic, while excessively loose muscles are hypotonic.
When applying acute pressure with deep strokes, a hypertonic muscle will release.
To be hypertonic means to be extremely tense. An example sentence would be: His calf muscle was hypertonic after the marathon.
Release
lateral rotation of humerus (upper arm)
Sarcomere
sarcomeres
flexion and lateral rotation of the neck
visceral smooth muscles cells function together as ONE (functional syncytium) multiunit smooth muscle act independently.
Cardiac muscle cells are mechanically, chemically, and electrically connected to one another, thus, the entire tissue resembles a single, enormous muscle cell. For this reason, cardiac muscle has been called a functional syncytium. This is also true of smooth muscle.
sarcomere
There is not a single muscle that rotates the upper arm. The name of the muscle that contributes in rotation of the upper arm is deltoid muscle.