Which condition involves both contraction and relaxation of muscles?

Clonus is a neurological condition characterized by involuntary, rhythmic muscle contractions and relaxations. It typically occurs when there is a dysfunction in the normal motor control pathways in the central nervous system. When a muscle is stretched, instead of simply relaxing, it responds with a rapid series of contractions that can be observed especially in the ankles, wrists, or other joints. This repetitive contraction and subsequent relaxation can be triggered by stimulus, such as passive movement of a limb. Clonus is often associated with conditions that damage the upper motor neurons, which control voluntary movement, leading to a lack of inhibition and resulting in this pattern of muscle activity.

The other options do not represent a condition that involves both contraction and relaxation of muscles. Antalgic gait refers to a limping posture adopted to avoid pain, dysphasia is a language disorder affecting the ability to communicate, and EOM palsy involves limited eye movements, typically due to nerve damage, without the characteristic rhythmic contractions seen in clonus.