I know you’ve been taught to stretch your horse, to have them do ‘tummy tucks’ and ‘pelvic tucks’ by your vet or bodyworker… But did you know those are just involuntary reflexes, and that the Stretch Reflexes are probably getting in the way of those being beneficial?

A reflex is a simple circuit in the nervous system, defined as a motor impulse that is reflected back to the muscle. (Criswell 1989).

Mammals have three types of muscles - smooth, cardiac and skeletal. The stretch reflexes discussed here only affect skeletal muscles - the muscles attached to bones and responsible for producing the forces that that move the body around and provide the dynamic elements of stability in biotensegrity.

There are all sorts of involuntary reflexes that can influence skeletal muscle tone and create restrictions or limitation on range-of-motion when they become habitual, like the startle reflex, withdrawal reflex, the symmetric and asymmetric tonic neck reflexes and crossed-extensor reflexes, the stretch/myotatic reflexes, and others. When the muscle contractions involved in these reflexes become chronic, meaning the agonist muscle stays shortened and their antagonistic muscles are automatically inhibited and held in a chronically lengthened state, the result is a horse whose default posture has become abnormal or deviant (aka crooked, asymmetrical, upside-down, shut-down, etc.) and whose forcibly lengthened muscles (sometimes referred to as “locked long”) are in a state of Stretch Weakness.

GOOD NEWS: These acquired postural abnormalities, and any other areas of chronic tension, can be reversed with the right somatic exercises that help the horse change their motor-output.

In this post, let’s talk about the myotatic reflexes and how and why to avoid them while doing Equine Hanna Somatics® (EHS).

Skeletal Muscles

There are two types of skeletal muscles, flexors and extensors - and they all have just one function: to contract.

Skeletal muscles have two types of muscle fibers: extrafusal and intrafusal.

"The extrafusal muscle fibers contract, providing the force exerted by the muscle. Small and arranged in parallel with the extrafusal muscle fibers are the intrafusal muscle fibers. Functioning as stretch receptors, they detect muscle length. An afferent nerve ending is connected to the capsule of the intrafusal muscle fiber. The intrafusal muscle fibers are found within the muscle spindles. The muscle spindles are mechanoreceptors: they respond to forces applied to the ends of the intrafusal muscle fiber." (Criswell p130).

Muscle spindles are the most important proprioceptors in the body.(Kroger & Watkins 2021)

Understanding the stretch reflexes can help you interpret horse behavior and the tension patterns you may observe in the horses body and way of going, and how to influence them.

In Equine Hanna Somatics we have one very specific goal: to help the horses nervous system reset the resting muscle tone of their skeletal muscles. Another way to say this is to help a body and brain let go of chronic or habitual tension. The result is that we can rapidly alleviate the pain or soreness associated with chronically tense muscles, and also improve range-of-motion and flexibility by allowing the skeletal muscles to easily achieve their full length, as needed. This is a game-changer for equestrians and equine bodyworkers!

What happens when you stretch?

When a skeletal muscle is stretched, the involuntary myotatic reflexes (aka ‘the stretch reflexes’) are triggered. These reflexes are involuntary, meaning they happen automatically and unconsciously.

What is the Muscle Stretch Reflex or Myotatic Reflex

There are two stretch reflex systems, monosynaptic and polysynaptic. The monosynaptic stretch reflex is as simple as the ‘knee jerk’ reflex aka patellar reflex. When muscle tissue is quickly stretched, like when your doctor taps on the tendon just below your kneecap with that little rubber hammer, there is an immediate contraction of the muscle that gets stretched – this is what makes your foot do a little kick. It begins with the sensory endings of the intrafusal muscle fiber, which synapses on the extrafusal muscle fibers in the same muscle. This reflexive firing of the muscle is involuntary, meaning it is out of your conscious control.

The polysynaptic stretch reflexes are more complex, involving a number of axonal branches of each neuron, creating a divergence of information. These complex stretch reflexes include the Golgi tendon organs, whose job is to decrease the strength of a detected muscle contraction, and the the coordination of agonist-antagonist muscle pairs. When an agonist muscle is excited by the monosynaptic stretch reflexes or motor impulses to create movement , the antagonist muscle is simultaneously inhibited via reciprocal inhibition.

Once the receptors in the muscle spindles sense the stretch, they send a quick signal from the sensory neuron straight back to the motor neuron that controls the muscle fibers and causes them to contract AGAIN – without ever consulting the brain. This is known as a ‘local reflex arc’ because it’s all happening at the spinal cord and peripheral nervous system level.

Now, here’s the real kicker –

The Problem with Stretching

The purpose of the myotonic stretch reflex is to maintain the current length of a muscle by bringing it back to it’s pre-stretch length.

In fact, the stretch reflex not only works to bring the muscle back to the same length it was before you stretched it, but it can even re-contract the muscle to be even shorter! Yikes!

This can be great for maintaining an upright posture and for preventing muscles from being over-stretched and damaged. But it’s not so great if you are stretching with the intent of making a muscle longer – and isn’t that why most of us were taught to stretch??? Well, dang. This means that while we are stretching to get more flexible, we are also working against the wisdom of the nervous system by triggering the stretch reflex. This is not just my opinion, this is 100% physiology.

It also means that when we stretch ourselves (or our horses) by accident, by moving too quickly or too far in one direction with a limb to catch our balance or when we are being pulled on, or by triggering involuntary reflexes (even a sneeze!) we are triggering the stretch reflexes.

This is why we tell you NOT to Stretch while doing Somatic Exercises, and why NOT to pull on your horse when doing Equine Hanna Somatics.

And, this is why doing reflexive tummy tucks for a horse with tight back muscles or a compressed thoracic sling, or pelvic tucks for a horse with a roached back or tight iliopsoas complex is not an effective way to help those muscles normalize their tone and improve their function or comfort… and can even make things worse.

How does Hanna Somatics work?

Rather than doing anything directly to the muscle tissue or fascia, like stretching or massaging it, when we do Somatic Exercises we invite the individual to change the motor-output from their brain to the affected area of their body. Another way to say this is that Somatic Exercises can influence the way the brain and muscles communicate in a way that most other types of exercise or ‘bodywork’ just can’t do consistently.

To get the brain to stop telling the muscles to be habitually shortened (aka tense or tight) and to re-establish a normal neutral resting length of both the extrafusal and intrafusal muscle fibers, we use a series of somatic exercises based on a natural reflex called pandiculation.

What is Pandiculation?

To put it simply, pandiculation is a polysynaptic reflex that involves the contraction and slow de-contraction of a muscle or a whole group of muscles. The purpose of pandiculation is to ‘wake-up’ or prepare the body for movement, by resetting muscles to their optimum resting length. Pandiculation happens spontaneously for all vertebrates, usually shortly after waking, or after sitting still for long periods. You have probably seen your cat or dog pandiculate after a nap! It looks like a big luxurious stretch, often accompanied by a yawn.

Doing voluntary pandiculation exercises is what sets Hanna Somatics and Somatic Yoga apart from all other modalities or methods. Voluntary Pandiculation, used strategically to target the most contracted and dysfunctional muscles first, is also the technique that creates such an incredibly high rate of success and the long-term lasting changes that are everyday occurrences with a Hanna Somatic Education® (or Equine Hanna Somatics) practices.

What is the difference between Pandiculation & Stretching?

Even though some of the somatic exercises can look similar to what some bodyworkers and trainers do as 'stretches' - and in fact some bodyworkers have taken to applying some of our EHS exercises TO horses as 'bodywork' - to trigger the effect of pandiculation, the horse must do a very specific type of movement that involves a concentric contraction of a muscle (or group of muscles) and then a very slow eccentric contraction of the same muscles - using motor output from their own brain to control their muscles and detect whether they are stretching or not. It's NOT Equine Hanna Somatics or effective Somatic Exercises if the practitioner is doing the exercises TO the horse, even if the horse is allowing the work and giving good feedback or enjoying it.

While doing Hanna Somatics, we actively avoid stretching, because triggering the stretch reflex (aka myotatic reflex) interferes with our goal of changing the allowing the muscles to lengthen passively, and to return to a neutral resting tonus. When we trigger the stretch reflex, we are also interfering with Pandiculation. And pandiculation is the reflex that can safely lengthen our muscles by changing the motor output from the brain and causing a reset of the resting muscle tone – the goal of Hanna Somatics, Equine Hanna Somatics and Canine Hanna Somatics.

Most Hanna Somatic Educators would never say that “stretching is bad” or that you should never do it… In fact, a little mechanical stretching can be helpful in loosening up stuck fascia and improving our body awareness by sending extra sensory feedback to the brain. BUT we do often find ourselves needing to educate our clients and interested folks about the stretch reflex, and why we actively avoid it during Somatic Exercises, in order to achieve the lasting effect of naturally supple and lengthened muscles.

RESOURCES

Kröger, S., & Watkins, B. (2021). Muscle spindle function in healthy and diseased muscle. Skeletal muscle, 11(1), 3. https://doi.org/10.1186/s13395-020-00258-x

Criswell, E. (1989) How Yoga Works: An Introduction to Somatic Yoga. Freeperson Press.