What is Muscle Tone?

When we talk about posture through the Equine Hanna Somatics lens, we are ultimately talking about muscle tone.

Muscle tone is the ongoing level of tension present within a muscle, even when the body is at rest.

Passive muscle tone refers to the passive viscoelastic properties of the tissue itself. Muscle tissue has both elastic qualities that allow them to return to shape, and viscous qualities that resist deformation and slowly dissipate force.

But muscle tone is not just passive tissue tension.

It is also actively regulated by the nervous system through tonic muscle contraction.

There are several layers to this active tone.

Resting muscle tone is the baseline level of tension that prevents the body from becoming completely slack.

Postural muscle tone organizes the body in relationship to gravity and helps coordinate how different body parts orient to one another.

Tonic contraction refers to the sustained low-level activity within postural muscles that create stability and support.

These are primarily slow-twitch muscles designed for endurance and efficiency. They work continuously in the background with very little conscious awareness.

Together, these layers create what we could think of as the horse’s habitual resting muscle tone: the steady level of tension and organization the nervous system defaults to automatically.

When that resting tone is neutral, the horse can organize effortlessly and move without unnecessary interference to range of motion, but when chronic increases in tone develop either above or below the vertebral column, posture begins to shift.

Over time, those patterns can become habituated.

In EHS, we often describe these as Green Light or Red Light postural patterns or even a combination of the two.

A horse with increased extensor tone above the vertebral column may organize into a Green Light posture characterized by a contracted back, elevated head and neck carriage, and camped-out limbs.

A horse with increased flexor tone below the vertebral column may organize into a Red Light posture characterized by shortened abdominals, a tucked pelvis, and camped-under limbs.

The important thing to understand is that these patterns are not simply “bad habits” or isolated training issues.

They reflect the nervous system’s current default organization and because that organization exists in the background automatically, the horse often no longer realizes they are holding those patterns.

That habitual resting tone then influences everything layered on top of it: posture, coordination, balance, movement quality, and available range of motion.

This is why, in EHS, the goal is to help the nervous system regain access to movement options that have gradually become obscured beneath layers of chronic contraction and habituated muscle tone.