No, the length of the muscle fibers does not change. In isotonic movements is when the length changes.
A muscle cell is a cell which can change length
Muscle Spindle
They measure the rate of change of length of a muscle.
Stretching a muscle beyond its optimal length reduces its ability to contract. This is because the muscle can be torn or damaged.
The muscle length will not change during a contraction.
it shortens
You will use the diaphragm muscle to control the length/strength of your breath.
Isotonic contraction
isometric contractions
The muscles in organs are called smooth muscle. Smooth muscle has short length and slow movement. It is involuntary unlike skeletal muscle.
concentric