What distinguishes spasticity from rigidity in terms of muscle response?

Spasticity is characterized by a muscle response that varies with the speed of movement, also known as velocity-dependent increase in tone. This means that when a muscle is stretched quickly, it exhibits an exaggerated response and increased tone, while slow stretches may result in less resistance. This characteristic helps differentiate spasticity from rigidity, which is marked by a constant increase in muscle tone that does not change based on the speed of movement.

The distinction is crucial in clinical settings, as it informs treatment and rehabilitation approaches. Understanding that spasticity can lead to a more pronounced response during rapid movement allows therapists to tailor interventions, focusing on managing this excessive tone during activities that involve quick movements.

Through recognizing these nuances in muscle response, practitioners can effectively assess conditions like cerebral palsy or after a stroke, where spasticity often presents. This contrasts with rigidity, where resistance remains constant regardless of how fast or slow a muscle is stretched.