I recently had a parent ask me, “What is low tone?” in response to a note she received from her child’s school occupational therapist. As an occupational therapist, I often talk about low muscle tone and this question was a reminder to me that parents do not always understand what these terms mean.
All of the muscles in our bodies have a resting muscle tone. Muscle tone is the “alert state” of muscles that allows them to respond to an outside force; such as a quick stretch or change of direction in the muscle. Muscle tone is involuntary and directly related to a child’s nervous system, in which the brain perceives the positions of the muscles. With normal muscle tone, the body can adjust to immediate postural or arm/leg movements and maintain its upright position against gravity. Normal muscle tone is high enough to support the body against gravity, yet low enough to allow movement. Muscle tone also allows a child’s muscles to quickly relax once the perceived change is gone.
A child with low muscle tone has muscles that are slow to initiate a contraction against an outside force and also cannot sustain a muscle contraction as long. In other words, the muscles “relax” quicker despite the outside force still being present. Muscle strength is different from tone, in that strength increases with voluntary repetitions of movement. Muscle tone improves with a more comprehensive treatment approach that is directed towards the “alert state” of the muscles themselves. The treatment approach focuses on the underlying sensory processing deficits which may be present.
These underlying sensory processing deficits are not alerting the brain of changes in body position. The areas of sensory processing which may be impacted are:
- Vestibular processing; which refers to a child’s response to movement. The vestibular system plays a powerful role in arousal, muscle tone, spatial orientation, balance, eye movements, and attention.
- Proprioceptive processing; which refers to the ability of the body to know where it is in relationship to itself and the environment. It occurs at the level of the joints and muscles. Receptors in the joints and muscles provide feedback to the brain and the sensory motor system that allow the body to move more effectively.
- Tactile processing; which refers to the way in which a child responds to touch, either seeking touch or avoiding it.
A child with low muscle tone may have mild and benign developmental delays. These children may also be at risk for developing poor balance and coordination, orthopedic abnormalities, learning disabilities, and language delays.
An infant with low muscle tone may have poor head control and resist propping on their tummies when awake. Babies will often seem to “slip out of your hands” and have trouble “stiffening” their bodies when you carry them. When lying on their backs, babies with low muscle tone will often rest with their arms and legs extended outward and sometimes resist bearing weight on their feet when held upright on your legs. Younger children with low muscle tone may tend to lean excessively forward when they are sitting up.
Older toddlers and children will tend to “W-sit” to reduce the challenge to their postural muscles. Children with low muscle tone may have difficulty learning to roll, sit, crawl and walk independently. These children often tire easily, complain about lack of energy, have difficulty sitting up while completing table top activities such as drawing, coloring or writing, and have a hard time sitting still or sitting on the floor. Low muscle tone is sometimes confusing to understand because a child may actually appear athletic. I’ve seen plenty of clients who could throw a ball accurately but their core strength was so weak that they could not do a single sit up or lift their chests and thighs up off the floor when lying on their bellies.
Muscle tone improves with a comprehensive treatment approach to improve postural control and address issues within the nervous system that help the brain perceive where the body is in space. Physical and occupational therapy often focuses on improving the delayed postural responses and protective reactions that are typical in children with low muscle tone. Occupational therapy will also focus on improving sensory processing in order to improve body awareness, balance and motor planning. Because low muscle tone is also associated with laxity or looseness in a child’s ligaments, physical therapy also aims to improve overall muscle strength to increase the support around the joints in the arms and legs.
If you have any further questions about low muscle tone, please join us for our workshop on October 27, 2011 at 7:30pm. Do not hesitate to contact us at (215) 545-0320 or firstname.lastname@example.org for a consultation or therapy screening to determine whether your child will benefit from therapy.