What are typical changes in muscle mass with immobility?

What are typical changes in muscle mass with immobility?

• A. Loss of muscle mass
• B. No change
• C. Increased muscle mass
• D. Increased flexibility

Answer: (A)

Immobilization leads to loss of muscle mass because the muscles aren’t being used and the body shifts toward breaking down muscle proteins. When mechanical loading on a muscle drops, signaling that drives protein synthesis (like the mTOR pathway) decreases, while pathways that degrade contractile proteins become more active. The result is a reduction in muscle fiber size and overall cross-sectional area, which translates to weaker muscles. This atrophy can begin within days of inactivity and progresses with continued immobilization. Other choices don’t fit because lack of change would ignore the disuse effects, increased muscle mass would require resistance or overload training, and increased flexibility is not a typical result of immobility and often accompanies other joint changes rather than true muscle mass gains.

Immobilization leads to loss of muscle mass because the muscles aren’t being used and the body shifts toward breaking down muscle proteins. When mechanical loading on a muscle drops, signaling that drives protein synthesis (like the mTOR pathway) decreases, while pathways that degrade contractile proteins become more active. The result is a reduction in muscle fiber size and overall cross-sectional area, which translates to weaker muscles. This atrophy can begin within days of inactivity and progresses with continued immobilization.

Other choices don’t fit because lack of change would ignore the disuse effects, increased muscle mass would require resistance or overload training, and increased flexibility is not a typical result of immobility and often accompanies other joint changes rather than true muscle mass gains.