Kas tonusu refers to the level of tension or firmness in the muscles at rest. It is an important aspect of muscle function, as it helps maintain posture and supports movement. A healthy muscle tone allows for smooth and coordinated actions, while abnormal tone can lead to issues such as stiffness or weakness. Factors influencing kas tonusu include physical activity, neurological health, and overall fitness. Conditions like cerebral palsy or multiple sclerosis can affect muscle tone, leading to either increased tension (hypertonia) or decreased tension (hypotonia). Understanding muscle tone is crucial for rehabilitation and physical therapy.