Hypotonia is a disorder that causes low muscle tone (the amount of tension or resistance to movement in a muscle), often involving reduced muscle strength. Hypotonia is not a specific medical disorder, but a potential manifestation of many different diseases and disorders that affect motor nerve control by the brain or muscle strength. Recognizing hypotonia, even in early infancy, is usually relatively straightforward, but diagnosing the underlying cause can be difficult and often unsuccessful. The long-term effects of hypotonia on a child's development and later life depend primarily on the severity of the muscle weakness and the nature of the cause. Some disorders have a specific treatment but the principal treatment for most hypotonia of idiopathic or neurologic cause is physical therapy and/or occupational therapy to help the person compensate for the neuromuscular disability.
An infant placed face down in a pool of water will begin to paddle and kick in a swimming motion. The reflex disappears between 4–6 months. Its survival function is to help the child stay alive if it is drowning so a caregiver has more time to save it. Although the infant will begin to paddle and kick, placing them in water is very risky. They swallow a large amount of water at the same time. It is advisable to postpone swimming lessons in infants until they are at least three years old.
A plantar reflex is a normal reflex that involves plantar flexion of the foot (toes move away from the shin, and curl down. An abnormal plantar reflex (aka Babinski Sign) occurs when upper motor neuron control over the flexion reflex circuit is interrupted. This results in a dorsiflexion of the foot (foot angles towards the shin, big toe curls up). This also occurs in babies under ~1 year, due to low myelination of the descending corticospinal tracts. As these tracts develop to adult form, the flexion-reflex circuit is inhibited by the descending corticospinal inputs, and the normal plantar reflex develops..