What part of the muscle is involved in the tendon that stays fixed during contraction?

The part of the muscle involved in the tendon that stays fixed during contraction is the origin. The origin of a muscle is the attachment point that remains relatively stationary when the muscle contracts. This is critical for understanding muscle movement, as muscles generate force by contracting and pulling on their respective tendons, which in turn affect the bones they are connected to.

During contraction, the muscle fibers shorten, but the origin does not move, allowing for a stable point against which the other end of the muscle, typically adherent to the insertion, can pull. This stability provided by the origin is essential for effective movement and force generation in activities such as lifting or running.

The insertion, in contrast, is the end of the muscle that moves during contraction, while muscle fibers refer to the cells that contract. The joint capsule is related to the structure encompassing joints and does not play a direct role in the origin or insertion points of muscles. Understanding the role of the origin helps illuminate how muscles function in a coordinated manner during physical activities.