The Myotatic Reflex

The Myotatic Reflex (sometimes myotactic reflex) is probably our body's most important and unrecognised defence mechanism. When it comes to making it safely through the day, nothing comes close to the myotatic reflex.

How the Myotatic Reflex Works

Muscles constantly monitor their own length and tension, and feed back changes in length or tension to the spinal cord. Without the myotatic reflex, controlled movement would be impossible.

The myotatic reflex starts in the muscle spindle, which constantly and spontaneously produces afferent impulses to the spine (and therefore the brain) – at rates between 5 and 50 times per second.

Any change in tension or stretch in the muscle will increase this feedback to spine and produce a rapid increase in muscle tone.

The Reflex Pathway

When a muscle is stretched, the muscle spindles are activated, which sends a signal through afferent sensory neurons to the spinal cord. The spinal cord then sends a signal back to the muscle through motor neurons, which causes the muscle to contract. This reflex contraction helps to resist the stretch and maintain appropriate muscle tone and movement.

Protection and Function

The myotatic (or stretch) reflex helps to protect the muscle from being overstretched, and also helps to maintain muscle length, which is important for proper muscle function and movement. The reflex works in conjunction with the opposing muscle group, the antagonist, to create balance and stability in muscle tone and movement.

By limiting the stretch of muscles, the myotatic reflex protects ligaments and joints from overstretching which prevents sprain, strain, tearing and dislocation.

Real-World Example: Walking Down Stairs

The myotatic reflex helps us walk down stairs safely. As you step down on a stair, the quadriceps muscle, which is located in the front of the thigh, has to lengthen or "eccentrically contract" to control the descent of the body.

As the quadriceps muscle is stretched, the muscle spindles are activated, which sends a signal to the spinal cord, triggering a reflex contraction in the muscle, to help resist the stretch and maintain muscle tone. The amount of contraction will be proportional to the input so that the same result can be achieved whatever load the person is carrying.

Joint Protection and Long-Term Health

The myotatic reflex prevents damage to joints. When it is working properly, joints are protected from excessive movement or strain.

If the myotatic reflex is inhibited, the joint will be damaged – causing pain initially, and osteoarthritis in the long term.

The Goal of Afferentology

Eliminating abnormal inhibition of the myotatic reflex is the ultimate aim of afferentology.

Only when muscles have their full nerve supply are they able to provide the support and feedback the body needs for repair and healing.