Many people seek out Rolfing® for help with their posture. They've spent years trying to correct rounded or slouching habits, and their efforts to "straighten up" and "keep their shoulders back" have not translated into any long-term improvements.
What's more, certain folks who deal with regular recurring pain (like hip pain, lower back pain, neck pain or shoulder pain) generally find significant relief from improving their sitting or standing posture.
Unfortunately, postural improvements can feel out of reach for many. The efforts that go into assuming a specific position can lead to new patterns of tension and strain, leaving many folks feeling like it's impossible to find ease at rest while also feeling upright and open.
Tonic Function as a Missing Link in Posture
For manual therapists like me, the link between poor postural habits and bodily discomfort is evident. But it can be difficult to resource clients in a way that empowers them with techniques and tools that will offer improved postural patterns that are both comfortable and sustainable.
That's why I feel exceptionally fortunate to have been introduced to Hubert Godard's model of tonic function during my training at the Dr. Ida Rolf Institute.
A two week long immersion into this topic fortified my understanding of movement principles, neuromuscular coordination, and muscle tone through the lens of our body's gravity response system—a key focus of Rolfing®—and provided me with new tools to share with clients to help them feel open and at ease in their resting posture. Which is why I'm writing this blog post for you today :)
To understand the theory of tonic function first requires us to understand the distinction between two types of muscles—delineated as tonic versus phasic muscles (tonic muscles, as you might guess, are the primary subject of the theory of tonic function). So let's get to know the term tonic and what it means in our muscular system...
What are tonic muscles?
In the discipline of physiology (the branch of biology that deals with the functions of living organisms and their parts), the term "tonic" is used to describe a physiological response which is slow and may be graded. When this term is applied to the neuromuscular system, the delineation between tonic and phasic asks how different skeletal muscles help us move through space.
Tonic muscles are best understood as compared to their counterparts: phasic muscles. There are 4 ways that these muscles differ:
Tonic and phasic muscles differ in function.
Tonic and phasic muscles differ in the makeup of their muscle fibers (and fatigue resistance).
Tonic and phasic muscles are innervated differently.
Tonic and phasic muscles tend to be found in different regions of the body.
1. Tonic and phasic muscles differ in function.
Tonic muscles maintain a steady level of tension or contraction, while phasic muscles produce short bursts of dynamic activity. Put differently, tonic muscles are associated with postural control and maintenance, while phasic muscles are involved in more dynamic movements.
2. Tonic and phasic muscles differ in the makeup of their muscle fibers (and fatigue resistance).
Tonic muscles tend to have more slow-twitch muscle fibers, which are better suited for sustained activity (and are more resistant to fatigue). Phasic muscles, on the other hand, have more fast-twitch muscle fibers, which are better suited for short burst, rapid movements (and fatigue more quickly).
3. Tonic and phasic muscles are innervated differently.
Tonic muscles are innervated by a different type of motor neuron than phasic muscles. Tonic motor neurons have a slower firing rate and a lower threshold for activation, allowing them to maintain a steady level of contraction over time. Meanwhile, phasic motor neurons have a higher firing rate and provide a strong, quick pulse of activity to spring phasic muscles into contraction.
4. Tonic and phasic muscles tend to be found in different regions of the body.
Tonic muscles are typically located closer to the body's center of mass and work to maintain a stable body position, especially during tasks that require a sustained posture.
Image Source: 8 Arms Bodyworks - "Resting Posture"
**There's still no such thing as a binary** (even when it comes to tonic and phasic muscles)
It's important to remember that bodies, muscles, and neuromuscular coordination vary widely. And as much time as I've spent thus far spelling out the differences between tonic and phasic muscles, the reality is that any given muscle or muscle group can have fibers that behave tonically and fibers that behave phasically depending upon stimulus and conditioning. As with any practice of categorizing or delineating "this" from "that," it's tempting to assume there's some clear line that can be drawn between tonic and phasic muscles. But, as per usual, the facts and the science blur the nice tidy borders between these boxes. And it's always worth remembering that, in any living system, clean straight lines are typically drawn, not found.
Where do tonic muscles come from?
We humans aren't the only critters who have muscles that can be organized on this tonic vs. phasic spectrum. Research has demonstrated the importance of tonic stabilizing muscles in our fellow mammals, birds, amphibians, reptiles, even crustaceans!
That's why most of the evolutionary theories behind tonic muscles suggest that they evolved as part of a primitive postural control system (i.e. came to the fore before all of us creatures started to evolve our own unique forms of life) to help embodied creatures of all shapes and sizes maintain body stability during movement, and to resist external forces (like wind or water currents).
Our uniquely human take on tonic musculature likely happened later, and was largely informed by the time in our evolutionary history when bipedalism (walking on two legs) emerged, and the ability to maintain an upright posture became essential for survival and daily activities.
Research suggests that the development of tonic motor neurons (part of what makes tonic muscles functionally unique) begins in utero, as the developing fetus begins to move and assume different positions in the womb. After birth, infants gradually develop the ability to control their posture and movement (through a process known as postural development). Tonic motor neurons play a key role in this process, as they provide the sustained level of contraction necessary to maintain a stable posture.
Tonic Muscles and Tonic Function (Your Body's Gravity Response System)
Have you started to sense the theme here yet? Tonic muscles are evolutionarily designed to help you stay upright in gravity. They ARE your postural muscles.
But, many of us have lost touch with how to recruit tonic muscles for the job, and instead we find ourselves relying on much larger (and more fatigue-prone) phasic muscles to try and help us stay upright.
But why would our bodies rely on large, phasic muscles to stay upright if it causes discomfort?
Here's the crux of the issue: the neuromuscular coordination required to recruit tonic muscles as a part of our gravity response system operates outside of our voluntary, conscious control.
If you think about an infant learning to lift its head, use its hands and arms, and—with age—learning how to sit upright, stand, and eventually walk, you can see just how little of that neuromuscular coordination is governed by a conscious, thinking brain. These little humans are simply exploring their environment and allowing their system to respond to the stimulus of their surroundings. And one of these constant sources of stimulus is gravity.
It is this same physiological system that governs our tonic muscles (aka deep postural muscles) as adults.
But unlike infants and toddlers who orient and respond to a variety of new environmental stimulus and positions in gravity throughout a given day (or week, or month, or year), our adult lifestyles tend to direct us towards the opposite.
We adults tend to move less than our younger counterparts. And even those of us that invest in a conscious workout routine or strive to stay active in spite of the cultural trends towards a sedentary lifestyle, our movements tend to become predictable and we are less likely to seek out variation in our routine.
Even active adults aren't typically getting enough variety of stimulus and orientation with gravity to help the deep postural muscles (aka tonic) muscles come on line. Movements that are conscious and repetitive don't fill the gap.
Put bluntly: The more we age the more boring our movement tends to become.
Let's examine what that means for your gravity response system:
The more static and boring (aka non-varied) your daily movement diet, the less stimulus your gravity response system receives from your surrounding environment and your orientation in space and gravity.
The less stimulus your gravity response system receives, the quieter the connection between your brain and your deep postural (aka tonic) muscles becomes.
The quieter the connection between your brain and your deep postural (aka tonic) muscles becomes, the less your tonic muscles respond to your position in gravity.
The less your tonic muscles respond to your body's position in gravity, the more your phasic muscles must compensate.
The more your fatigue-prone phasic muscles compensate for your fatigue-resistant tonic muscles, the more likely your body is to experience discomfort and chronic tension patterns from everyday living.
So, what can we do?
If our deep postural (aka tonic) muscles and our gravity response system operate outside of conscious, voluntary control - then how can we begin to think about recruiting them to participate in the act of keeping us upright so that our sore, tired phasic muscles can take a break?
The answer may surprise you.
Research suggests that we can change the "setting" of the gravity response by changing perception, emotion, or the meaning of a given situation.
It's like a side door into the gravity response system. You can help the body perceive new stimulus by changing what you're paying attention to, by shifting your feeling state, or by using a new lens to evaluate and categorize your circumstances.
Standing Upright—this tutorial demonstrates how to work with your gravity response system to activate tonic muscles and find a sustainable standing posture. Check it out>>
I typically help clients tune into their gravity response system by shifting their perception / what they're paying attention to within their bodies.
If you've watched any of my tutorials related to supported sitting or supported standing, you know that I invite a lot of "felt sense" work (the work of feeling your body from the inside out). I ask my clients all the time to feel landmarks within their body so that they may feel where their body is in space, and to imagine making slight adjustments based on what they are feeling.
This act of feeling from the inside, of cultivating a "felt sense" of your body, falls within the framework of interoception. I'm sure I will write a blog post about this in the near future, but if it's your first time hearing about interoception, I'd definitely suggest Googling it. The more we understand about interoception the more we see its central importance to human health and wellbeing.
Definitely try this at home...
The introductory technique I teach my clients for activating their gravity response system involves 2 points of orientation: ground and sky.
Orienting to ground. Pause for a moment and see if you can feel, from the inside, the places in your body that are in contact with the ground. Maybe that's where you're actually contacting the floor. This usually means feeling into the bottoms of your feet if you're standing, maybe other surfaces of your legs if seated on the floor. If you're sitting, also feel the base of your pelvis where it's in contact with the surface you're sitting on (the surface that provides your pelvis its connection to ground). Now, this is important, can you deepen your sense of connection between those places and the ground? You don't have to physically exert yourself, just imagine you were reaching more firmly into the earth from those particular places in your body. It can be as quiet as a whisper, you could think of "releasing" more of yourself into the support of the earth. The goal is to subtly shift your perception of your connection to ground by deepening it.
Orienting to sky. Now that we've found a downward orientation, we turn our attention in the upward direction. Keep a soft awareness of the places you're in contact with the earth, now notice how the crown of your head floats skyward. Feel the space above the crown of your head and imagine softly reaching the crown of your head a bit more into that space. Notice if you feel yourself squeezing or tensing anywhere, and use your mind to soften those places. Common places to tense are the shoulders, chest, and hips. If you find yourself arching your back or bringing your shoulder blades behind you to try and get taller, allow yourself to reset. Feel back into your points of contact with the earth, then invite more ease as you reach the crown of your head skyward. On the spectrum of imagining versus physical efforting, lean more toward imagining this act.
That's it!
How are you feeling in your body? Do you feel a sense of uprightness and ease?
You may not feel them (because they fire at a low rate and are very fatigue resistant) but this technique serves to stimulate your deep tonic (aka postural) muscles and, at the same time, soften your larger phasic muscles that are likely overly-tired and deserving of a break.
This is simple stuff, but that doesn't make it easy. Many of us have pre-conceived ideas of what "good posture" looks and feels like, and it's rarely easeful.
With this technique, you're not forcing your body to look a certain way or attain any specific position. Instead, you're practicing finding a new orientation to space and gravity. Put differently - you're changing your perception and - just maybe - also changing the meaning of what it is to feel yourself rooting down and rising up from the inside out.
And that, my friend, is just one way to ignite your body's gravity response system! Hopefully, with some practice, you find this technique to be low on effort and high on ease. My clients who practice this at home attribute a huge portion of their progress with chronic pain and discomfort to this work, learning how to soften their exhausted phasic muscles and turn on their deep tonic muscles to help them find ease while being upright in gravity. It really is an absolute game changer.
This blog post is the second in a two part series focusing on how we organize our bodies in gravity. To read the first part (all about the Ground Reaction Force) - you can check it out here. If this was interesting to you and you'd like to experience its application in practice, you can book a session with me here.