Atrophy of muscle in a cast is primarily due to which of the following?

Atrophy of muscle in a cast is primarily due to a lack of muscle stimulation. When a muscle is immobilized, such as when it is placed in a cast, it experiences a significant reduction in physical activity. This decrease in mechanical loading and stimulation leads to disuse atrophy, which is characterized by a reduction in the size and strength of the muscle fibers.

Muscle contraction is essential for maintaining muscle mass. Regular use of the muscle helps stimulate protein synthesis and encourages the muscle cells to maintain their size and functionality. When the muscles are not used for an extended period, as in the case of immobilization, the balance shifts towards protein degradation, leading to atrophy.

Other factors, such as blood supply or metabolism, do play a role in muscle health, but the primary driver of atrophy in this scenario is the lack of neuromuscular stimulation and activity. Without the necessary stimulation from the nervous system, the muscle fibers cannot maintain their mass or perform their functions effectively.