What are the effects of immobilization on muscle?

• A. Muscle hypertrophy and increased strength.
• B. Muscle atrophy, fatty infiltrates, severe fibrotic changes.
• C. No muscle changes occur.
• D. Decreased nerve conduction only.

Answer: (B)

Immobilization leads to disuse atrophy of skeletal muscle. When a muscle isn’t regularly loaded, anabolic signaling declines and proteolysis rises, so muscle fibers shrink and strength falls. Over time this atrophy is accompanied by changes in tissue quality, with fat cells and fibrous connective tissue gradually replacing or intermingling with muscle fibers, which further reduces muscle function. This combination—loss of muscle mass with fatty infiltration and fibrotic changes—best matches what happens with immobilization.

Hypertrophy and increased strength would require loading or resistance activity, not immobilization. No changes would be inaccurate because muscle rapidly responds to reduced use. Decreased nerve conduction is not the primary or most characteristic effect of immobilization; the neural pathways stay largely intact while the muscle tissue wasting and replacement take place.