The Mobility-Stability Continuum
A New Look At Joint Health
by Mike Robertson
Mobility and stability go together like peanut butter and jelly...
spandex and cardio... Eric Cressey and Tony Gentilcore.
Over
the past few years, gentlemen much smarter than myself have been
discussing the importance of mobility and stability at length. Stuart
McGill, Mike Boyle, Gray Cook, Bill Hartman, and Eric Cobb all come to
mind. It started off quietly, but this topic has slowly grown
to the point where I felt the need to bring the pendulum back to
center. Somewhere along the way, we lost sight of the big picture. This
may sound weird coming from a purported "mobility" guy, but hear me
out. I want to clear up some misconceptions regarding
mobility training and help you to better understand how truly
inter-related mobility and stability are. Along the way, we'll find out
what other influences (outside of mobility and stability) could be
affecting your performance.
Two Sides of the Same Coin Mobility
and stability are complementary in nature. When you strive to improve
mobility at a joint, to some degree you sacrifice stability. It works
the opposite way as well; the more stable you make a joint, the more
you inherently restrict its mobility.
Before
we go any further, let's get the semantics out of the way. Here are the
Bill Hartman-approved, "simple" definitions:
Mobility — The ability to produce a desired movement.
Stability — The ability to resist an undesired movement. When
examining mobility, the key factors involved include the architecture
of the joint(s) at hand, soft-tissue length, and neural control over
the surrounding muscle groups. Stability is created via a blend
of active and passive influences. Passive constraints include the joint
capsule, ligaments, and the joint architecture itself, along with more
active constraints like motor control of surrounding musculature,
muscular strength, etc. Each joint serves a specific purpose —
to produce a given movement. Mike Boyle took the concept to another
level when he introduced his "joint-by-joint" approach to training.
Here's the Reader's Digest recap: It appears as though each joint
requires either more mobility training
or more stability training. Even
more interesting is that it appears they alternate in fashion. A joint
which needs more mobility is surrounded, above and below, by a joint
that needs more stability, and the opposite is true.
The chart below depicts each joint's primary need, according to the joint-by-joint approach (1):
Joint — Need Foot — Stability
Ankle — Mobility
Knee — Stability
Hip — Mobility
Lumbar Spine — Stability
Thoracic Spine — Mobility
Scapula — Stability
Gleno-Humeral Joint — Mobility
Elbow — Stability
This
view is beautiful in its simplicity. However, it has led to plenty of
detractors, mostly people who hold their own dogmatic views or those
who don't fully understand the concepts. Unfortunately, some
people seem to think that the joint-by-joint approach is purely black
and white. If the joint-by-joint table says the hip needs more
mobility, then dammit, you're going to give it more mobility!
If all you've got is a hammer, everything looks like a nail. The hip
generallyneeds
more mobility. However, there are certain individuals who have
excessive hip mobility and therefore require more stability. The
joint-by-joint approach gives you a base understanding of the movement
requirements at each joint, but it can't be applied injudiciously and
without first making proper assessments. The chart doesn't replace the
assessment, but it speeds things up and makes it more efficient.
It's Easy, But Not
That Easy We'll
use the knee as an example. According to the joint-by-joint approach,
the knee needs more stability. But in fact, a knee with restricted
sagittal plane mobility (flexion and extension) would be at an
increased risk of injury.
Instead
of broadly saying that we need to stabilize the knee joint, we'd be
better off by saying that we need to stabilize it in the frontal and
transverse planes, while mobilizing it in the sagittal plane. Perhaps
a better way to state this is that the joints in the "mobility" section
of the column have more freedom of movement (in multiple planes) when
compared to the "stability" joints. Instead of thinking black and
white, we need to think of things in a grayscale fashion. The Mobility-Stability Continuum The
mobility-stability continuum piggybacks upon the joint-by-joint
approach, and hopefully takes it to the next level. It's not
necessarily "new," but I hope it'll enhance your understanding of what
you already know. Hopefully we are in agreement that all joints need
some degree of mobility and
some degree of stability. The key is to understand how much mobility/stability we need at each specific joint.
| Stable | | | | Mobile |
 |
| Knee | Elbow | Scapula | Hip | Shoulder |
If
we examine the continuum above, on the left we have joints that
traditionally need more stability. On the right, we have joints that
need more mobility. If we understand the architecture of each joint,
this concept becomes even clearer. Let's look at the knee and
elbow, two joints similar in architecture and function. They should
require an equal amount of stability, right? Not quite. The
elbow is comprised of the humerus, the radius, and the ulna. So while
you can flex and extend your elbow, the inclusion of pronation and
supination via the radius tells us it needs a little bit more mobility
than the knee. The knee, even though it
canmove slightly into internal and external rotation, should only be trained to flex and extend.
Another
example is the difference between the hips and shoulder joints. They're
both similar in nature (ball and socket joints), but the femoral head
sits much higher and tighter within the joint than the humeral head
does. The hip socket is also much deeper than the glenoid,
which accounts for more differences in joint mobility. So while they're
similar in architecture, the hip will naturally be more stable than the
shoulder.
The
trickiest joint, in my estimation, is the scapulo-thoracic joint. I've
heard both sides of the equation argued. Some will say it needs more
mobility, while others will say it needs more stability. I'm not sure
that we need equal training of both, but let's just say we need to
understand the multiple functions surrounding the scapulae and train
accordingly. If you don't have adequate stability, it's only a
matter of time until you suffer from some sort of rotator cuff injury.
Recent literature states that in patients with gleno-humeral
instability, their scapula is unstable 100% of the time!(1) I
don't know about you, but I think 100% is pretty damn often. With
regard to training, we generally need more stability with regards to
scapular protraction, retraction, and depression. On the other
hand, if you don't have adequate mobility in the scapulae (especially
into upward rotation), you're again at risk for impingement injuries.
In her book,
Diagnosis and Treatment of Movement Impairment Syndromes, Shirley Sahrmann ranks scapular downward rotation syndrome as the most prevalent upper extremity issue.(2) What does this mean to you? Absolutely nothing...
if you are cool with never putting your hands over your head for the rest of your life. Bill Hartman and I wrote an entire article about this. After
all, we can get 120 degrees of shoulder abduction or flexion from our
gleno-humeral joint, but if we aren't getting that necessary 60 degrees
of upward rotation from the scapulae, it's going to lead to issues down
the line.
This would severely impact our "raise the roof" skills. The
take home message here is this: Stop thinking about things in black and
white, mobile and stable. Instead, think about how mobility and
stability work in unison. You can't have one without the other. The key
is understanding the architecture of the joints themselves, the
soft-tissues surrounding them, and how they're used in motion
throughout the day.
Accueil 
