Hypotonia is decreased muscle tone. Muscle tone is the amount of tension or resistance to movement in a muscle while at rest. It is different from muscle strength which is how much force a muscle can apply. For example, you may be able to do sit-ups which are a measure of abdominal muscle strength but if the belly is not firm then there is low muscle tone. Many people with hypotonia also have muscle weakness. Hypotonic infants are also called "floppy infants" because the low muscle tone and decreased strength of the neck and trunk muscles make the children floppy like a rag doll.