Hypertonia and hypotonia are terms used to describe abnormalities in muscle tone. Tone is the level or amount of resistance within a muscle when a limb is moved while an individual is at rest. Normally, muscles do not fully relax but have some degree of continuous contraction necessary to control and sustain postures against gravity. Frequently, individuals diagnosed with intellectual and developmental disabilities have co-occurring issues that result in abnormal muscle tone that can affect their ability to move efficiently. Muscle tone can be too high, which is characteristic of hypertonia, or too low, which is a characteristic of hypotonia. These abnormalities may be present at birth, early in a child’s development, or emerge at certain points during childhood. Developmentally, hypertonia and hypotonia may remain ...