Muscle tone

Muscle tone or residual muscle tension refers to the continuous and passive partial contraction of the muscles or their resistance to passive stretch during a resting state. In other words, when we are in a relaxed state our muscles maintain a bit of contraction in them which gives them a “springy” feel.

 

Unconscious nerve impulses maintain the muscles in a partially contracted state. If a sudden pull or stretch occurs, the body responds by automatically increasing the muscle’s tension, a reflex which helps guard against danger as well as helping to maintain balance. Such near-continuous innervation is a default condition for muscles. Both the extensor and flexor muscles are involved in the maintenance of a constant tone while at rest. This helps maintain an upright posture.

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Hypotonia or low muscle tone are shown as muscle flaccidity; where the limbs appear floppy, stretch reflex responses are decreased, and the limb’s resistance to passive movement is compromised.

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Hypertonia or high muscle tone can present as either spasticity or rigidity. These cause resistance to movement in a variety of ways.