Britannica
Sources used in this answer
How does prolonged inactivity lead to muscle atrophy?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
muscle
The structure of striated, or skeletal, muscle. Striated muscle tissue, such as the tissue of the human biceps muscle, consists of long fine fibers, each of which is in effect a bundle of finer myofibrils. Within each myofibril are filaments of the proteins myosin and actin; these filaments slide past one another as the muscle contracts and expands. On each myofibril, regularly occurring dark bands, called Z lines, can be seen where actin and myosin filaments overlap. The region between two Z lines is called a sarcomere; sarcomeres can be considered the primary structural and functional unit of muscle tissue.
Prolonged inactivity leads to muscular atrophy primarily because the maintenance of muscle mass and function depends on regular use. When skeletal muscles are immobilized—such as when a limb is placed in a cast—they undergo rapid wasting characterized by the shrinkage of individual muscle fibers.12
While the exact biological mechanisms are not fully understood, inactivity is associated with several physiological changes:
- Reduced Metabolic Capacity: Inactive muscles exhibit a consistent reduction in oxidative capacity.1
- Nutritional and Vascular Deficits: Diminished activity leads to decreased blood supply and impaired nutrition within the tissue.2
- Structural Changes: Over time, muscle fibers may undergo fragmentation and disappearance, often being replaced by fat cells and connective tissue.2
Importantly, these changes are generally reversible through targeted muscle-strengthening exercises. While disuse atrophy is typically less severe than atrophy caused by nerve damage, it remains a significant consequence of prolonged immobilization.12