Recently I encountered the following Internet commentary on this same topic,
so it is apparent that the misuse of biomechanics terminology may be
escalating, simply because some folk are relying in good faith on textbooks
or information sources that may not be accurate or complete. This is why it
is so important that teaching texts should be as accurate as possible.

<The definition of a force couple is two parallel forces of equal magnitude,
but opposite direction, applied to a structure at equal distances from the
center of the mass. Muscles behave very differently in isolation than they
do in multi joint activities. We always talk about force couples at the
shoulder joint. But they also occur elsewhere in the body. Think about what
glenohumeral motions occur in the transverse plane during the throwing
motion. Internal and external rotation, and shoulder horizontal adduction
are two of them. The question is, can we use this particular force couple to
help neutralize the traction forces at the shoulder during follow through?>

***This definition refers to a “couple”, not a “force couple”. The word
“force” is redundant, since the use of a “couple” in biomechanics is defined
on the basis of forces being involved. Including the word “force”simply
introduces ambiguity and inaccuracy. A “force-couple” is a specific
combination of a force and a couple that is used in mechanics and statics as
the equivalent of a force acting on a body. Thus, in analysing the
kinesiology of a physical system, a force may be replaced by a “force-couple”
or conversely, a “force-couple” in a system may be replaced by a force.

If one examines the action of the thoracoscapular, glenohumeral, pelvic and
other physical subsystems, it will be seen that understanding the difference b
etween a “couple” and a “force-couple” can facilitate the analysis of such
systems. Unfortunately, the use of the term “force-couple” seems to have
been seriously overused and misapplied by simplistic popularisation of
Schafer’s definition of a couple by Paul Chek and others, namely:

“FORCE COUPLES A mechanical couple represents a special case of a pair of
parallel forces of equal magnitude that act in opposite directions some
distance apart and tend to produce rotation…..”
(Schafer RC “Clinical Biomechanics – Musculoskeletal Actions and Reactions”
1987 )

Simply omit the use of the word “force” and all likelihood of confusion with
an entirely different mechanical concept will be avoided.

————————–

Further comments read as follows:

<The definition of a force couple is two parallel forces of equal magnitude,
but opposite direction, applied to a structure at equal distances from the
center of the mass. Muscles behave very differently in isolation than they
do in multi joint activities. We always talk about force couples at the
shoulder joint, but they also occur elsewhere in the body. Think about what
glenohumeral motions occur in the transverse plane during the throwing
motion. Internal and external rotation, and shoulder horizontal adduction
are two of them. The question is, can we use this particular force couple to
help neutralize the traction forces at the shoulder during follow through?

A force couple helps keep the pelvis from drifting laterally during all
phases of pitching in baseball…..>

***This commentary and my earlier remarks about “force couples” leaed us to
some interesting questions:

1. Are we justified in taking about “force couples” or “couples” at the
shoulder and other joints?

2. In each case of joint action mentioned, is it entirely correct that there
are “two parallel forces of equal magnitude, but opposite direction, applied
to a structure at equal distances from the center of the mass.” ?

3. Should we be referring to moments, couples or other more intricately
linked systems involving non-collinear forces? Can we reduce the many
muscles, multi-articular systems to collinear forces and, thence, to couples?

4. Are we justified in analysing these linked systems in terms of active
muscular action without considering the role played by collinear and
non-collinear passive connective tissues at different stages of movement?

5. Are we justified in analysing the above systems as true “couples”,
because this presumes that no translation whatsoever occurs?

6. Since several forces, moments or couples can be involved in all joint
action, should we not analyse movement in terms of “force-couples” (in their
accurate sense as special combinations of forces and couples) rather than
“couples” (of only two equal and opposite collinear forces)?

Dr Mel C Siff

< http://www.t-mag.com/html/body_122back.html >

PART 2

<<Lahad et al concluded that sufficient evidence was unavailable to recommend
the use of mechanical back supports for the prevention of back pain. In
another study conducted by the National Institute for Occupational Safety
and Health, prophylactic use of back belts for healthy workers was not
recommended because of a lack of scientific evidence promoting their
benefit. There are also many other studies indicating belt use provides no
significant improvement in performance or reduction in the user’s chance of
injury. >>

***Virtually all of the studies that Chek quotes to condemn the use of a belt
are drawn from the world of manual labour or research studies with average
volunteers in which belts are worn for prolonged periods. It is
scientifically invalid to extrapolate such findings from the setting of
CHRONIC belt usage to the setting of occasional ACUTE belt usage for very
heavy or maximal competitive lifting.

<<Davis’ Law is demonstrated and well known by physical therapists who treat
neurological injuries; stimulating the surface of the body produces
stimulation of the muscles served by the same nerve root. Therefore,
repeatedly “pushing outward” against the belt, which is encouraged by the
belt through sensory-motor stimulus, is likely to develop and perpetuate
faulty recruitment patterns. >>

***This statement that superficial methods of kineasthetic manipulation
perpetuates faulty motor patterns (see Siff & Verkhoshansky “Supertraining”
1999, Ch is entirely one of personal opinion and not supported by any
quoted research. On the contrary, PNF and neurodevelopmental methods in
physiotherapy rely heavily on manual contacts and touch to teach correct
optimal motor patterns. It is not the stimulation of the surface of the skin
which may elicit faulty patterns, but the inappropriate use of such
stimulation. This sort of remark is grossly misleading and inaccurate, as
any experienced physical therapist and neurologist will tell us.

<<If belts really did improve trunk stability, then the lifter would be able
to use them for a given period of time, remove the belt and experience
improved performance when lifting; THIS IS NOT THE CASE! …..

If indeed belts did improve proprioception, the user would be able to take
the belt off after a period of use and have improved proprioceptive sense or
“position sense” while lifting. This would constitute a learning effect; I
have never experienced this to be the case! Belt users become dependent upon
their belt, making the belt more of a crutch than a training device. >>

***Once again, the same remark may be applied to the wearing of shoes and the
new skintight swimming and cycling outfits which, besides reducing
aerodynamic drag, apparently enhance proprioceptive sensitivity and muscle
activation. Anyway, many lifters who wear belts for maximal lifts have shown
that they are quite capable of lifting the same loads without belts, but
choose to wear belts for attempting new maximal lifts because they consider
that belts may offer enhanced safety under those extreme conditions. It is
very common for athletes in the most demanding situations to use specific
protective or ‘ergogenic’ devices, so why would this be so reprehensible for
competitive lifters?

Remember that the lifting of maximal loads is not undertaken every day or
even every week, but only on occasional maximal training days or training
competitions that are weeks or months apart. As I have written many times
before, it is the manner and duration of belt wearing that may deem it
inappropriate, not simply because belts “weaken” everyone under all
circumstances.

<<The only way to restore function of the deep abdominal wall is to use
various forms of biofeedback (described below)…..

It is very valuable to use other extroceptive (sic) stimuli, such as athletic
tape to improve kinesthetic awareness. As the patient learns, the need for
tape is reduced, and eventually the tape is eliminated. String is also used
as a form of biofeedback during movement training and is particularly useful
in restoration of deep abdominal wall function during functional movement
training.>>

***Here we have a fascinating contradiction! Chek spent a great deal of
space in denouncing the value of a lightly worn belt as a mode of offering
mechanical feedback, but here he is extolling the virtues of using
inextensible tape (a la Jenny McConnell taping etc) to play the same role.

Let us repeat what he said earlier:

<<If indeed belts did improve proprioception, the user would be able to take
the belt off after a period of use and have improved proprioceptive sense or
“position sense” while lifting. This would constitute a learning effect; I
have never experienced this to be the case! Belt users become dependent upon
their belt, making the belt more of a crutch than a training device. >>

So, the use of belts ruins proprioception, but the use of taping does not!
Any jury presented with this blatantly contradictory information would
dismiss his evidence as being unreliable, because he is clearly admitting
that devices like tape (and, by implication, certain types of belt) CAN
improve kinaesthetic awareness. The device being used may be different, but
the underlying principle remains the same. CASE CLOSED!

***Finally, let us reinforce the case a little more strongly – Chek even
quotes the following reference which supports the use of belts. Is this not
another contradiction?

<< 35. Cholewicki J., Juluru K., Radebold A., Panjabi M.M., Magill S.M.
Lumbar spine stability can be augmented with an abdominal belt and/or
increased intra-abdominal pressure. Eur Spine J 1999;8(5): 388-95. >>

So, I reiterate, that, if you are going to use a belt or straps, then just do
so intelligently and selectively! Note that I am not stating that one cannot
lift successfully and safely without a belt or that one cannot develop a very
strong trunk without using a belt – I am simply stressing that sometimes it
may be appropriate or useful to astutely use a belt in a given situation.
What I oppose is any blanket or “allness” statement which creates another
item of dogma in the strength training world.

Dr Mel C Siff

< http://t-mag.com/html/body_121back.html >
< http://www.t-mag.com/html/body_122back.html >

He has not submitted Part 3 of this series, so, if he is still working on it,
it will be interesting to see if my review influences what he submits. These
two article already suggest that he has taken some of our earlier criticisms
to heart, because he is now admitting in this series that breath holding does
indeed stabilise the trunk.

HOW TO BE BACK STRONG & BELTLESS

PART 1

<<Regardless of your opinion about the origin of man, if you believe in God,
you have to wonder why he didn’t provide weight belts as standard-issue
equipment. On second thought, maybe he did, and we just don’t know how to use
them correctly.>>

*** Exactly the same remark may be applied to the wearing of shoes and it is
entirely spurious. We might even have said that we should have retained a
hairy cover all over our bodies to protect us from the sun and other extremes
of climate. Why we should have evolved to lose something that protects us
from our environment is anyone’s guess. A remark like that has been used by
Luddites, the Amish folk, the Taliban and others who reject many
technological advances on a similar basis.

<<Today, our understanding of the stabilizer system is at an all time high,
thanks to the works of people like Richardson, Jull, Hodges, Hydes, Vleeming,
Snidjers and Gracovetsky. >>

*** This is misleading, because no theory of spinal function has been
regarded as pre-eminent over any others. In fact, there is even more
disagreement over spinal function than there has ever been. The number of
theories about spinal action may be at an all-time high, but our
understanding is certainly not yet at an all-time high. It is still highly
theoretical and by no means definitive, though it is very exciting to try and
decode some of the complex biomathematical models (which Chek, unfortunately
is not trained to be able to do).

<<As you are likely aware, when lifting a heavy object or exerting yourself
to throw or move an object such as in work or sports, it is natural to hold
the breath. Holding the breath under load is associated with increased
tension in the diaphragm. …

Practical experimentation in the gym will show that the trunk is stiffer
when filling the lungs as opposed to not filling the lungs with
inhalation….>>

***These remarks are most revealing, because Chek has constantly disagreed
with me and several others (in several Internet exchanges that still exist in
the archives of several user groups) on breath holding as a perfectly natural
concomitant to spinal stabilisation. He has always been vigorously opposed to
breath holding to stabilise the spine. Instead he has placed an exaggerated
emphasis on “pulling the abs in” and trying to voluntarily activate
transversus abdominis (TVA) during all stages of squatting and lifting. It ap
pears as if our criticism of his views may have caused him to change his mind.

<<More recently, it has been shown that IAP does provide a stiffening effect
on the lumbar spine, but that IAP is most effective at stabilizing the spine
when applied in concert with co-activation of the erector spinae muscles…..

Although, as suggested by Gracovetsky, we can not rely on muscles alone
because mathematical modeling shows that Olympic athletes would not be strong
enough to lift the loads they currently are lifting during competition. We
must look to the fascial system of the body for a missing link, the hydraulic
amplifier effect…

It has also been suggested that IAP does not stabilize the spine. Standing
firmly against the notion that IAP provides any significant stabilizing
mechanism for the spine are Gracovetsky and Bogduk…..>>

***Note well that the models of Gracovetsky and others whom he mentions,
though compelling in some respects, are by no means unopposed by other
theorists and researchers, especially some of the world’s most erudite
biomechanists. What Chek has done is a commendable cut-and-paste collage job
of information from various sources, but he has failed to go beyond a
literature retrieval stage of the literature review. A true review retrieves
the necessary information, then compares and analyses it, then, if the author
has specific scientific or research skills, he offers his own views and
models. Anyone can cut and paste from books, articles and Medline, but not
anyone can intelligently analyse the material and go beyond the obvious.

<<The hydraulic amplifier effect, originally theorized by Gracovetsky to
increase the strength of the back muscles, was later proven mathematically to
increase the strength of the back muscles by 30%…. The hydraulic amplifier
mechanism is composed of the TLF (thoracolumbar fasciae) surrounding the back
muscles to create a relatively stable cylinder…. >>

***While Chek has given a reasonable summary of how some of the trunk
musculature can act like an hydraulic lift, he has not shown that he
understands the significance of the “amplifier” part of the spinal model.
This is a very significant omission, because a knowledge of the dynamic
process of mechanical amplification (including amplifier “gain” and feedback
control) is vital to an understanding of lifting, stabilising and injury.

<<What modern researchers have been able to do is more clearly define two
major stabilizer systems of the body, the inner unit and the outer unit. The
stabilizer system considered as our “God-given weight belt” is the inner
unit…..

The Inner Unit serves to stiffen the axial skeleton in preparation for work.
The Inner Unit muscles are A) Transversus Abdominis and the posterior
fibers of obliquus internus, B) Diaphragm, C) Deep Multifidus,
D) Pelvic floor musculature….

The outer unit consists of many muscles such as the obliquus externus,
obliquus internus, erector spinae, latissimus dorsi, gluteus maximus,
adductors and hamstrings working in concert with the inner unit musculature
and fascial systems. …..

A simplified version of the inner/outer unit systems, seen in Figure 9,
depicts a pirate ship’s mast as a human spinal column. While the inner unit
muscles are responsible for developing and maintaining segmental
stiffness, the bigger muscles, shown here as guide wires, are responsible for
creating movement. >>

***The accompanying figure depicted the spine as a system of guy wires
supporting the mast of a ship. Significantly, this model excludes any
transverse members on the sails or the fact that the hull, like the rest of
the human body, does not provide a stable base. This incomplete spinal model
allows us to understand in part why it is nowadays so fashionable to talk
about “core stabilisation”. The latter misleading concept is based upon a
system which excludes the role of peripheral stabilisation (of which I have
written elsewhere) and the systems nature of motor control. One of the
problems with models and analogies is that, in attempts to simplify complex
processes, they can omit details which can lead to some very defective
conclusions.

Division of the muscles of the trunk into “inner” and “outer” systems, while
often being convenient for the sake of simplifying the complexity of the
spine, sometimes proves to be a rather limiting model of trunk functioning.
Interestingly, Chek, while sketching this model in a superficially
attractive way, has not explained if this mast and guy rope depiction of the
spine or Gracovetsky’s model constitutes a frame, truss or machine (recalling
that frames are designed to support loads, whereas machines are designed to
transmit or amplify forces or couples).

Chek, in previous discussions, has always evaded my attempts to make him
understand the difference between moments, couples, force couples and related
mechanical concepts with some entirely irrelevant personal retorts. This
latest article makes it very apparent that he really should have attended to
this deficit in his knowledge base. He might then have come across
biomechanical models of the spine which rely on a systems theoretical
approach which does not regard the spine a system of guy ropes and rigid
members and which do not implicate the fasciae in the role suggested by
Gracovetsky and others.

Other models regard the spine as a cantilever system, while yet others
examine the spine as a suspension system. In these models, there is no
necessity to divide the muscles into inner and outer units, but as an entire
system which stabilises the spine in terms of the least energy principle.

By selecting only one favourite model of the spine, he has been biased to
make some misleading and unjustified conclusions and applications in the rest
of his material, especially the practical applications.

Dr Mel Siff

The next post discusses Part II of Paul Chek’s Article!