What does "muscle tone" mean?
When I worked as a paediatric occupational therapist, I was often asked this question by parents. Here is a simplified overview of what the term "muscle tone" means, with a brief description of both high muscle tone and low muscle tone.
Unlike the pic of this boy showing off his muscles, muscle tone does not refer to the strength of a muscle!
Muscle tone is the state of muscle tension inside a muscle or muscle group when it is at rest.
Normal muscle tone means that there is the right amount of “tension” inside the muscle at rest, and that the muscle is inherently able to contract on command. Put simply, you can “tell” your muscle to stop and start and it does what you want, when you want!
An example would be: You are sitting in your chair, arms resting on your lap (your arm muscles are “at rest”). You decide to have a sip of your coffee, which is on the table next to you. With your normal muscle tone, you reach out with your arm, your hand makes connection with your cup of coffee, and you bring it back to your mouth. No spills, no fuss!
High muscle tone means there is too much tension in the muscle at rest. In other words, the muscle is tight and tense even though it is not doing anything. A child with spastic cerebral palsy has high muscle tone, which causes his arms and legs to be tightly contorted. When his arms and legs are not regularly stretched and moved through physical therapy, then “contractures” may occur, which mean less and less range of movement is possible.
In the coffee example I gave above, the person with high muscle tone would have to concentrate very hard and expend a lot of effort overcoming the tension in his biceps in order to stretch out his arm. He may well end up moving his whole body towards the coffee, as the tension in the arm muscles is too high to be overcome with ease.
Low muscle tone means there is not enough tension in the muscle when it is at rest. The muscle may have a slightly mushy feel to it, and there is a lack of graded control of the muscle when it is being used (graded control means that just the right amount of movement and effort is used as appropriate to the task at hand).
To use the coffee example again, when you decide you want to have a sip of coffee, there is not enough tension in your muscles at rest. So you use a bit extra momentum, maybe by flinging your arm out! You bump the cup a bit, get your fingers around the handle and then drag it back, but the cup is heavy, and you use too much oomph at first (to overcome the lack of “tension” in your muscles) with the result that the coffee sloshes out!
A child with low muscle tone may well battle to sit upright at a desk for any period of time, and may slouch over like the child in this picture.
It is important to remember that muscle tone is on a continuum – you can have normal muscle tone that is a bit on the low side or a bit on the high side.
Your muscle tone affects your postural control and your postural stability. Postural control and postural stability give you the “background” control of your body that is necessary for helping you to stay upright and to stabilise you during movement.
In children, postural stability needs to develop in 3 main areas: Head/neck muscles, shoulder girdle muscles and core muscles (trunk muscles). A lack of stability in these areas will have an impact on both their
fine motor skills
gross motor skills.
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