Movement and Posture

Posture is a bit of a polarizing topic. On one side of the spectrum is the argument that posture doesn’t correlate to pain and therefore doesn’t matter; on the other are the posture police, the ones for whom posture cure everything from neck pain to the common cold and should be thought about at all times. 

If we look at static posture, the link between posture and pain is weak, at best. A review of the literature by Eyal Lederman concluded the long held belief that “correcting” posture will decrease pain is flawed, given the fact research does not show a causative link between posture and pain (1). The literature also does not show sitting by itself is a risk factor for developing low back pain (repeated exposure to whole body vibration for professions such as helicopter pilots is another story) (2). 

“Okay,” you might be thinking, “but what about alignment for moving? That has to matter a little bit, right?”

It turns out, the posture control researchers (apparently, that’s a thing) believe posture and movement aren’t two separate things. They consider movement “a series of postures,” (Holmes, 1922)(3). Our posture and, by extension, our movement are dependent on our ability to balance. Balance is the result of the muscle-stretch reflex. This reflex receives information from these neural inputs: vestibular, proprioceptive, teleceptive (vision), and exteroceptive (touch). 

The goal of balance is to maintain the body’s center of mass. The center of mass (COM) is located at approximately the 5th lumbar vertebrae. During quiet standing maintaining COM should feel effortless  (3). Even though there doesn’t appear to be much movement when a person is standing, there is always a little bit of movement, called “spontaneous sway.” When you close your eyes, the sway will increase unless you counteract it by increasing muscular contraction.

The COM is different in these two pictures because the fifth lumbar vertebrae is literally in a different place in these two positions. 

This should make sense. One of the ways the body senses balance is with the eyes; take that away, and you need to compensate with one of the other senses (in this case, proprioceptive) to maintain the same stability. 

A brief note on proprioception:
Remember, proprioception is our ability to sense our body and movement; proprioceptors are sensory receptors located in muscle spindles that send information regarding joint angle, muscle tension, and muscle length to the nervous system (4).

If you have a client with limited hip mobility and you ask him to touch his toes by flexing the hip, when he folds forward, you will likely see movement in either the thoracic or the lumbar spine. Why? Because the person is trying really hard to move from his hips; when he runs out of hip mobility, to successfully accomplish the task, he will move from somewhere else. 

What happens if you work with the client for a while on improving hip flexion? Maybe he does breathing work to influence pelvis position, performs isolation exercises to improve proprioception and mobility, and integrates motor control and strength in the position. 

Six weeks later, there should be a change in how the person accomplishes the task. His degrees of freedom during hip hinging will increase. This change in hip joint awareness will likely find its way into other exercises.

On the other end of the spectrum is the person with a lot of joint mobility, which doesn’t always translate into proprioception (5). In fact, people with benign joint hyper mobility syndrome consistently demonstrate a harder time knowing where their lower limbs are located in space.

Why does this matter? For starters, you might want to choose different exercise variations for the hypermobile person than for the stiff person illustrated earlier. With the example above, once you point out to that person he flexes his spine when he gets to end-range, he will likely be able to feel himself doing it. This makes it easier to not do it. With the individual with BJHS, he probably won’t feel himself flexing the spine. In order to get him to not flex his spine, first he has to be able to feel where his spine is located in space. Next, he needs to feel what it’s like to have the hip move by itself, followed by feeling the hip and spine move together. Finally, he should be able to keep the spine quite and move the hip. This (usually) takes tactile feedback of some sort, or visual feedback, and often requires a bit of creativity on the trainer’s part.

Posture and movement:
Okay, so proprioception influences how we move. Back to this posture business. What about dynamic posture?

Remember up above where I said the body’s center of mass is located at the level of L5? And that the goal of balance is to maintain the body’s center of mass? As soon as we move, our center of mass is displaced. How we are able to maintain balance is going to depend on several factors. Let’s consider what happens if a person begins running.

When a foot hits the ground while running, there are ground reaction forces (GRF) that occur, placing load on the joints. When a person runs so that there is a lot of vertical movement of the center of mass (imagine the L5 vertebrae hopping up and down), there tends to be more GRFs (6). 

It should make sense how lots of up and down movement wouldn’t be very efficient and would lead to extra force. (This isn’t to say there aren’t elite runners that don’t move up and down. There probably are, since there are exceptions to every rule). For most of us, however, running with more horizontal displacement COM (moving forward, rather than up) would probably lead to a more pleasant running experience.

Limb posture at initial contact during running also affects the amount of GRF. This could more simply be thought of as how you are maintaining your balance while moving forward.

The person that runs like Phoebe from “Friends” is less efficient that the person that runs like Ryan Hall. (We aren’t making any claims regarding injury. We are simply looking at economy).

Less efficient; flip side, probably burning more calories than a HIIT workout

Efficient; has to run many, many miles to burn the same amount of calories as Phoebe.

Running is one example, but if you look at most movements, you should be able to identify the COM and determine if the balance strategy adopted by the individual is economical or not. 

Perturbations:
When there is a perturbation (disturbance to posture), the central nervous system responds in a way that maintains balance. This is accomplished by the visual, vestibular, and somatosensory systems working together to provide the appropriate response (3).

Interestingly (at least to me), when perturbations are high, the postural muscle system keeps the COM fairly still (imagine someone trying to push you over); when perturbations are present at a low frequency, the COM becomes more fluid and “goes with the flow” (imagine rocking in a rocking chair) (7).

If you need someone to learn how to be more rigid, choosing exercises where the perturbation is enough to elicit a response. For instance, having someone plank with his forearms on a stability ball and pushing on the ball at different places will cause the central nervous system to respond by increasing muscle activity to keep the COM fairly still. Another example would be learning how to slackline (I am working on this right now. Finding the right amount of stiffness without over-bracing is an entirely different challenge than other things I’ve tried). 

Conversely, if you are working on teaching someone how to be more fluid and responsive, gentle rocking movements tend to work well. I frequently use the barrel rolling exercise seen here; the center of mass gently moves. If you do hands on work, you could even passive move the person, asking him to follow, rather than fight, your guided movement. 

Coaching and cueing:
Perturbations regularly come from the environment; one of our goals as movement professionals is to give people tools to manage their environment in a more effective way and remain uprightIf we only cue people on what muscles are firing (internal cues), we are doing a disservice. It takes away from the ability to respond to challenges. 

“Stable yet flexible movement patterns do not develop by learning techniques precisely, but through self-organization from complexity,” (8). Does technique matter? Yes, in the same way that posture matters (increases efficiency, gives more options to the individual), but if we teach people to perform every single plank in exactly the same way through internal cueing, we are taking away the system’s ability to self-organize. 
 
I used to be an over teacher. I wanted everyone to do exercises and yoga postures “right.” I was afraid of people hurting themselves if they did it wrong, and was convinced getting everyone to feel specific muscles was going to prevent injuries from happening. It wasn’t until I let that go and really began allowing people to use the environment through external cueing that I realized how fully capable the human system is.

I frequently work with clients who are convinced their transverse abdominis isn’t firing, or their gluteus medius is weak, or their serratus doesn’t function. And while maybe that’s true, maybe that’s not, (I don’t do EMG testing, so I don’t know), what I do know is which muscles are firing matters far less than how the system is self-organizing to maintain balance during movement. This isn’t to say I never use internal cueing; for clients that don’t fully understand how their joints move, I find asking them to feel the muscles moving the joint is extremely helpful. Like all things, finding balance in our cues and choosing the right cues for the right clients is critical for success.

Posture and touch:
Exteroception is one of the ways the central nervous system determines how to balance. Light touch provides enough somatosensory feedback to improve stability in individuals with poor balance (9). Touch gives the brain reference points for its location in space and can be utilized to improve posture and balance.

One of the tricky aspects of improving a person’s self awareness during movement is teaching people how to feel areas that, when asked, they don’t have any sense of at all.

Take, for example, the ischial tuberosities, or “sitting bones.” During sitting, feeling the sits bones against the chairs gives an individual a sense of where he’s balanced. 

It’s not uncommon for new clients to tell me, “I can feel my left one but not my right,” when asked if they can feel their sitting bones against a chair. An easy way to alter this is to provide more feedback by rolling a very small towel and asking the person to place it under the right sitting bone. This increases the amount of pressure, and gives a little bit louder signal to the brain. When the towel is removed (usually) the sitting bones will feel even or the right will fee a little bit heavier. The person suddenly has a tactile reference point.

Conclusion:
Posture is dependent on a variety of factors. While it doesn’t correlate to pain, the ability of the central nervous system to self organize and maintain balance is critical for a sense of ease with movement. A few of the ways posture can be altered include:
Increasing degrees of freedom at a joint
Increasing rigidity and decreasing COM movement
Increasing fluidity and allowing the COM to move
Identifying COM and determining if the movement strategy supports trajectory of COM
Allowing the individual to interact with the environment and self organize
Improving tactile awareness and giving the individual reference points

There are other factors, including visual and vestibular, which I didn’t discuss but are important inputs for balance and stability. Posture is complex and, like most things, there really isn’t an ideal that is perfect for everyone; however, as movement coaches, using the tools we have available to allow a person to move the COM in a way that maintains balance usually leads to an effective, enjoyable movement experience. 

Yours in health and wellness,
Jenn
 

References:
Lederman, E., (2010). The fall of the postural-structural-biomechanical model in manual and physical therapies: exemplified by lower back pain. CPDO Online Journal, 1-14. http://www.cpdo.net/Lederman_The_fall_of_the_postural-structural-biomechanical_model.pdf
Lis, A.M., Black, K.M., Korn, H., & Nordin, M., (2007). Association between sitting and occupational LBP. European Spine Journal, 16(2), 283-298.
Gollihofer, A., Taube, W., and Nielsen, J.B., (2012). Routeledge Handbook of Motor Control and Motor Learning.
Goble, D.J., Coxon, J.P., Van Impe, A., Geurts, M., Doumas, M., Wenderoth, N., & Swinnen, S.P., (2011). Brain activity during ankle proprioceptive stimulation predicts balance performance in young and older adults. Journal of Neuroscience, 9(31), 16344-16352.
Smith, T.O., Jerman, E., Easton, V., Armon, K., Poland, F., & MacGregor A.J., (2013). Do people with benign joint hyper mobility syndrome (BJHS) have reduced joint proprioception? A systematic review and meta-analysis. Rheumatology International, 33(11), 2709-2716.
Wille, C., Lenhart, R., Wang, S., Thelen, D., & Heiderscheit, B., (2014). Ability of sagittal kinematic variables to estimate ground reaction forces and joint kinetics in running. Journal of Orthopedic Sports Physical Therapy, 44(10), 825-830.
Schmid, M., Bottaro., A., Sozzi, S., & Schieppati, M., (2011). Adaptation to continuous perturbation of balance: regressive reduction of postural muscle activity with invariant or increasing oscillations of the center of mass depending on perturbation frequency and vision conditions. Human Movement Science, 30(2), 262-278.
Bosch, F., (2015). Strength Training and Coordination: An Integrative Approach. 2010 Publishers: Netherlands. 
Baldan, A.M., Alouche, S.R., Araujo, I.M., & Freitas, S.M., (2014). Effect of light touch on postal sway in individuals with balance problems: a systematic review. Gait Posture, 40(1), 1-10.