How does aging affect muscle mass and function?

• A. Hypertrophy with aging
• B. Sarcopenia - loss of muscle mass and strength with aging; fewer motor units, reduced neural drive, slower contraction, and less regenerative capacity.
• C. Muscle mass remains stable but strength declines
• D. Increased motor units with age

Answer: (B)

Aging leads to sarcopenia, the progressive loss of muscle mass and strength. As people get older, motor neurons die and the number of motor units declines, so fewer motor units are available to activate muscle fibers. The remaining units may reinnervate some fibers, but overall capacity drops, and neural drive to muscles becomes less efficient. At the same time, muscle fibers—especially fast-twitch Type II fibers—tend to atrophy, and there’s a shift toward slower fiber characteristics, which speeds up contraction decline and reduces explosive power. The ability of muscles to repair and regenerate diminishes with age due to reduced satellite cell activity and hormonal or inflammatory changes, so recovery from wear or injury is slower. All of these changes together explain why aging is associated with both reduced muscle mass and weaker, slower muscle function, precisely what sarcopenia describes.