Skeletal muscles are made up of hundreds of elongated cells known as muscle fibers. These fibers are composed of actin and myosin, proteins with contraction capacity and which form thin and thick filaments, respectively.
When a muscle contracts and shortens, one of its extremities usually remains fixed, while the other (more mobile) end is pulled towards it, resulting in movement.
The insertion is the distal end of the muscle that moves during contraction, ie it is the end attached to the bone that moves (moving point).
