IPHREHAB : MUSCLE TONE

IPHREHAB

Muscle Tone

Muscle tone refers to the amount of tension or resistance to movement in a muscle.  

Muscle tone (a different phenomenon than muscle tension) is the continuous and passive partial contraction of the muscles. It helps maintain posture and declines during REM sleep.

Muscle tone is what enables us to keep our bodies in certain position or posture. 

Changes in muscle tone is what enables us to move.  For example, to bend your arm to brush your teeth, you must shorten (increase the tone of) the biceps muscles on the front of your arm at the same time you are lengthening (reducing the tone of) the triceps muscles on the back of your arm. 

To complete a movement smoothly, the tone in all muscle groups involved must be balanced.  The brain must send messages to each muscle group to actively change its resistance.

Purpose

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.

The presence of near-continuous innervation makes it clear that tonus describes a "default" or "steady state" condition. There is, for the most part, no actual "rest state" insofar as activation is concerned.

§In terms of skeletal muscle, both the ex tensor muscle and flexor muscle use the term tones to refer to the "at rest" or normal enervation that maintains current positions of bones.

§Cardiac muscle and smooth muscle, although not directly connected to the skeleton also have tonus in the sense that although their contractions are not matched with those of antagonist muscles, their non-contractive state is characterized by (sometimes random) enervation.

§Many people don't understand the difference between muscle tone and muscle strength.

§True muscle tone is the inherent ability of the muscle to respond to a stretch. For example, if you quickly straighten the flexed elbow of an unsuspecting child with normal tone, the biceps will quickly contract in response (automatic protection against possible injury). When the perceived danger has passed, which the brain figures out really quickly once the stimulus is removed, the muscle then relaxes, and returns to its normal resting state.

§The child with high tone or "spasticity" has over-reactive response to the same stimulus. When his arm is stretched, the biceps tightens at an even more rapid rate, and the rate of recovery is much slower, even after the stimulus is removed. Full relaxation is difficult to achieve, so the muscle stays taut for an extended period of time.

§If another stimulus is added before the muscle has a chance to recover (which happens often during normal movement in the everyday world), the muscle contracts again, becoming tighter. Because this child's muscles never truly rest unless he is asleep, the long term result is tighter, shorter muscles with reduced joint range. This is typically seen in the child with spastic CP.

§The child with low tone has muscles that are slow to initiate a muscle contraction, contract very slowly in response to a stimulus, and can not maintain a contraction for as long as his "normal "peers.

§Because these low-toned muscles do not fully contract before they again relax, they remain loose and very stretchy, never realizing their full potential of maintaining a muscle contraction over time.

§These are the "floppy" children who have difficulty maintaining any posture without external support .

§Somewhere deep in the muscle are receptors responsible for detecting changes in muscle length.

§ These receptors then tell the brain there is a stimulus, and the brain tells the muscle to contract in response.

§There are numerous feedback loops to tell the brain whether the muscle has responded appropriately, needs to contract again, relax or whatever...

§In addition, there are receptors that tell where each joint is located in relation to all the other body parts that help to determine position in space, etc.

§ A delay in perception, decoding, or transmission anywhere along the neural pathways will result in a change from an optimal response, or "normal" tone. 

§Muscle tone occurs at an involuntary level. We can effect changes in muscle responses with sensory integration treatment techniques that increase the "alert state of the muscle" by bombarding it with sensory stimuli and improve the brains ability to perceive changes in muscle length, preventing it from accommodating to stimuli.