Inability to contract a muscle when stimulated is called.

• A. Muscle fatigue
• B. Muscle sprain
• C. Muscle atrophy
• D. Muscle hypertrophy

Answer: (A)

When a muscle loses its ability to contract despite stimulation, the situation is described as fatigue. This occurs after intense or prolonged activity because the muscle’s energy reserves (like ATP and glycogen) become depleted and metabolic byproducts build up. These changes interfere with the processes required for contraction, including the release and reuptake of calcium in the muscle fibers and the function of the cross-bridges that generate force. So the muscle can still receive neural signals, but its mechanical response diminishes, leading to an inability to maintain contraction.

The other terms refer to different concepts: a sprain is a ligament injury around a joint, atrophy is a wasting or shrinking of muscle from disuse or disease, and hypertrophy is an increase in muscle size from training.