Co-existence of Mobility and Stability

“I am stable and I am mobile.”

“My now is always moving.”

 INTRODUCTION

My long journey with the body, my movement practice, studies and experiential moments have brought me to a place that is always moving. I can sense and see the body’s process moving through many dimensions. 

I am a teacher of teachers and have shared how I synthesized the information out in the world of body knowledge. I have had incredible teachers and studied many effective body methods. It is a common thread to learn movement theories such as alignment principles, modifications for special populations, and the importance of stability and mobility.

 A Buddhist monk once said to me, always question anything I say. I have always questioned what has been said to me to fully understand the message and how I can implement it. Working with the human body, I have always taken the lessons and worked on the body. At times, it has not worked for the client or myself. Being in the now with the client gives me the answers to the lessons that I questioned. The process of evolving as I am implementing what I learned gave me the ability to help people move better. I encourage movement teachers to question the principles taught, explore what does work and be all right with changing your beliefs.

Movement theory # 2, alignment being #1, stability and mobility are factors in movement mechanics. One limb is stable as the other swings forward to take a step. We are instructed to work on our pelvic stability or lumbar stability to help eliminate back pain. It is this theory that I had to question from a personal experience not only for my own body but those of my clients. It rarely helped. What I found was the co-existence of stability and mobility helped me identify movement patterning that made a significant change not only in the function but more importantly, the feeling of resilient strength and body support.  Let me begin by giving you some information to ponder and question.

Defining Stability

It is almost impossible to define stability without mobility. Stability is the ability to control force and control movement under changing circumstances.[1] It is not holding one part of a body still while moving another. 

The human body is living in a gravitational force with forces moving through it from above and from below (ground forces). We are adapting to forces both from within our body and from outside. To remain upright, the visual, vestibular input as well as joint and connective tissues are players in regulation of the upright position. However, we are not fixed in an upright position. We move in multiple dimensions and perform a variety of movements everyday. Then we have the unexpected force that challenges our ability to remain grounded and not fall. When are we truly stable? It is when we feel balanced, adapt to forces and move with strength and ease. Instead of using the word stable, use good motor control, which gives us the sense of being stable.

Whether we are standing, sitting, or moving into and out of a posture as in Pilates, yoga or fitness, what is stable is the fact we can move off our base of support and return toward the center over that base of support.

 Moving off the base of support, is a torque at the joints and the response of the reflexes is to come back over the support to feel balanced and safe. This is an automatic response from the nervous system and the ability of the connective tissues (fascia) to transmit and disperse the force through its viscoelastic properties.

Stability and the Center of Gravity

What is and where is the center of gravity (CoG) in the human body? In the anatomical position, the CoG is found approximately at S2. The line of gravity is the direction of the force of gravity toward the center of the earth and moves through the CoG in the body. This is what you feel when standing balanced on both feet and a one-legged stance. During movement, the location of the CoG changes. There are many variables to the location of the CoG. And the base of support changes such as balancing on one shoulder or sitting on one hip. Also, the proportions of an individual’s body will also affect the location of CoG. When the line of gravity moves away from the center of the base of support, then the body reacts though the righting reflex described above to bring the body back to balance. 

With permission from Handspring Publishers

The Center of Pressure (CoP)

We are weighted bodies, mass moving through space on a surface. The contact points on the ground can be our feet, pelvis or any body part. The Center of Pressure (CoP) is a term given to the point where the pressure of the body is in contact with the ground. For an example, in gait analysis, the CoP is the points on the bottom of the foot. In gait, the CoP moves with the step beginning at the heel at the time of heel strike and moves anteriorly in a S shape throughout the step, ending near the toes at toe-off. 

The CoG and CoP play together in movement when the CoG moves so does the points of pressure on the base of support. 

The small excursion of the CoP creates a more stable posture. A shift of CoP is a postural sway, a righting reflex effect from neuromuscular control of the small contractions of muscles in your body to maintain an upright position. Ideally, the body should be able to generate quick CoP transitions that just exceed the current position of the center of gravity and accelerate it into the opposite direction in order to maintain balance. 

Body Sway & The Center of Pressure (CoP)

The shift of CoP is a postural sway, a righting reflex effect from neuromuscular control of the small contractions of muscles in your body to maintain an upright position. Ideally, the body should be able to generate quick CoP transitions that just exceed the current position of the center of gravity and accelerate it into the opposite direction in order to maintain balance. If you stand with your eyes closed, you will feel a small swaying of your body. As you are swaying, you can feel the soles of the feet pressure on the ground changing adapting to the sway.

Altered sway patterns are evident in people with disease and the ageing process.[2] Other issues include low back pain, damage to sensory tissues, decreased motor control and loss of proprioception. [3]

Mobility and Flexibility

There is a difference. Flexibility is how far a joint can move, the range of motion without restriction. It requires extensibility of the soft tissues (the myofascia) that cross the joint. Mobility is how the joint itself moves. Mobility requires strength and control within the range of motion. For example, how far someone can move his or her leg into flexion (hamstring flexibility) or how is the hip joint moving relative to the pelvis and are the hamstrings able to contract in this range. Improved mobility improves balance[4] through the adaption strategies of the nervous system. 

Training Stability and Mobility

In some approaches, stability is emphasized over mobility and in others increasing mobility (or flexibility) is preferred. Focusing on each alone does not change someone’s poor motor control, or help improve better movement patterning. The whole system of movement, the co-existence of stability and mobility, needs to be addressed matching the client’s capability. 

A proper assessment and understanding of the individual’s movement patterning is necessary to determine the best combination of stability and mobility work needed. And it may change. 

A combined approach of both mobility, stability with movement re-education helps improve balance, lessens or eliminates discomfort in the body and improves one’s physical performance. 

[1] Therapuetic Exercise: Foundations and Techniques Seventh Edition, by C. Kisner, L. Allen Colby and J. Borstad 2018 F.A. Davis Company

[2] J Hum Kinet. 2016 Sep 1; 52: 75–83. Published online 2016 Sep 10. doi: 10.1515/hukin-2015-0195

[3] J Phys Ther Sci. 2018 Aug; 30(8): 1099–1102. Published online 2018 Aug 7. doi: 10.1589/jpts.30.1099

[4] Medicine & Science in Sports and Exercise; “Quantity and Quality of Exercise for Developing and Maintaining Cardiorespiratory, Musculoskeletal and Neuromotor Fitness in Adults: Guidance for Prescribing Exercise” by C.E. Garber etal; American College of Sports Medicine 2011