Mel Siff Blog

The following letter was sent to one of the professional physical therapy
groups. Since it focused on the rather trendy cuurent fad of “core
stabilisation”, I thought that this discussion would also be of value here.
Far too many self-proclaimed authorities on back pain, trunk stabilisation
and core stabilisation are proliferating some rather dubious beliefs about
these topics and it about time that some far more cautious science were
applied to them.

Here is the original letter:

<< I’ve just been awarded a research bursary and am planning to investigate
the possible link between hamstring strength and core trunk stability. I’m
planning to measure concentric/eccentric hams strength intially, send
subjects off to do hams strength work, transversus abdominus strength work
and placebo exercises. I’ve been able to get lots of literature re hams
strength, transversus abdominus (mainly Hodges, Jull and Richardson) and hams
injury prevention. What I haven’t been able to get is much information on
hamstring/muscular trunk control interaction. Anybody out there able to point
me in the right direction? >>

Here is my response:

***Just a small point about which I have written before – how does one assess
“core stability” statically or dynamically under conditions in which
peripheral stabilisation does not play a significant role in the overall
stabilisation process or confound the results? For instance, if one wishes
to assess “core stability” in a standing position, then how do we rule out
the major role played by the lower extremity musculature in the process?

Moreover, stability is not necessarily a result of adequate strength, but the
amount of “strength”, force or torque exerted at crucial stages of joint
action throughout any given movement. If someone produces inappropriate
patterns or timings of motion, then, no matter how strong a given muscle may
be, then stability will be severely compromised. This point often seems to
be forgotten in many studies of relationship between injuries and muscle
strength. Though the intrinsic strength of a muscle may be adequate in the
execution of a given task, it may not be utilised efficiently in that or
other tasks.

Moreover, if strength is adjudged to be adequate as estimated by static or
isokinetic tests in a given action, this does not imply that strength under
other conditions will be adequate. We simply cannot ignore the vital fact
that strength is not only the result of muscle action, but of neuromuscular
facilitation in response to specific stimulation in a given motor task. It
is not valid to extrapolate findings from isolated joint testing to a process
as multifactorial as dynamic stabilisation.

In this regard, articles such as the following can be very revealing:

Zajac FE & Gordon MF(1989) Determining muscle’s force and action in
multi-articular movement Exerc Sport Sci Revs 17: 187-230

Andrews JG (1985) A general method for determining the functional role of a
muscle J Biomech Eng 107: 348-353

Andrews JG (1982) On the relationship between resultant joint torques and
muscular activity Med Sci Sports Exerc 14: 361-7

What does all of this imply for the researcher? Well, it means that the
research protocol, and possibly the title of the project, needs to be devised
very carefully to take these problems into account. One has to be especially
careful as to how one defines and measures “stability”, especially the
“stability” of a portion of a dynamically linked system. So far, I am not
very convinced that many researchers are adequately addressing this problem -
maybe you could take a significant step forward to rise above the
perpetuation of some dubious traditional and relatively unchallenged
hypotheses. Best wishes in your task!

Mel Siff
Denver, USA

Here we are witnessing a discussion bwteen Mel Siff and another distinguished member on the Supertraining Forums

Member<< I might take issue with some of this and ask for greater clarification.
While it is true that for general purposes a muscle is “measured relative to
its resting, unactivated length”, the relationship between lengthening and
shortening is relative to the extremes of the specific action being examined
and would seem to have nothing to do with “resting, unactivated length”….

While it is true, that the “attempt” to contract against opposing force
provides tension to the muscle in all three muscle action/contractions, true
contraction “only” occurs when the filaments actually “slide”, providing
a “shortening”. So even though we might be able to loosely term the act of
tensioning, “contracting”, we would be acknowledging that the “attempt to
contract” is “understood”. >>

Mel Siff:

***I was clarifying the definitions and analysis of muscle action according
to what is accepted in standard high level texts and was not trying to create
a new body of knowledge, because literature that I came across did not
reflect an adequate degree of accuracy on the topic. You have offered
comments which apply to muscles in different states of excitation, including
altered cognitive states, which intentionally have been excluded from the
accepted definitions because they are acknowledged not to be true resting
states. It would also help if you provided some references to support any
opinions, so that we don’t simply end up having a jolly good rumble in the
playground of speculation.

Member:

<<It is also true that due to the elastic nature of the “muscle complex” that
it is possible to have a small amount of “shortening” during an isometric or
eccentric action, this action is limited to the elastic properties and “is
not” representitive of the total action in these cases.>>

Mel Siff:

***This is not exactly correct, since the sliding filament model of muscle
and photomicrographs of muscle action show clearly that the actin-myosin
units shorten and thereby tension the other non-contractile elements in the
muscle complex. Also, there are elastic and viscoelastic components in the
muscle complex, so that the issue is not one of simple elastic extension.

Member:

<<I think we more accurately would say during a “forced lengthening” eccentric
action, the muscle “attempts” to contract. >>

Mel Siff:

***No, whether the action is “forced” by a heavy load or allowed to happen
voluntarily when a person lowers a light load, the muscle will contract. It
does not “attempt” to contract – it contracts. Muscle contraction is not a
matter of ‘half-hearted’, semi-committed action, but the result of all or
nothing excitation of muscle fibres. If there are any “attempts” to initiate
a motor action, then this process happens at a neural level, not at a
muscular level.

Member:

<<I am pressed to see that a true contraction (shortening) can happen under
these conditions. Even though, as I have stated, a muscle has a degree of
elasticity that may allow a small amount of actual contracting (within the
limits of structural integrity), I think somehow we are confusing the
“attempt to contract” with the actual “act of contracting”. The resistive
action in the muscle to a “forced lengthening” is not called an eccentric
contraction. It is called an eccentric action (or attempt to contract
against an active/superior force)>>

Member:

*** How can elasticity allow for contraction? Elasticity is always
associated with lengthening in extensible tissues such as the muscles and
elastic bands. This elasticity and possibly some ’sliding’ within the muscle
complex contribute to the electromechanical delay associated with the
activation of a muscle from its relaxed to its contracting state.

You will notice that I referred to eccentric “action” throughout my post, so
that this comment has no bearing on what I wrote. I take great care not to
confuse action with contraction, as do any biomechanists working in the same
field. As noted above, the concept of “attempting” to contract is not a
local muscular process or even one of spinal motor reflex action.

In one of my recent posts I even mentioned that the resting length in some
cases (as in individuals suffering measurement of muscle length is a relative
one. I simply emphasized that there happens to be a well-accepted definition
of resting (unexcited) muscle length in every individual.

Member:

<<Biomechanically, the two actions (concentric-eccentric) are distinct and
different. You might simply say that one acts as a brake and the other acts
as a motor.>>

Mel Siff:

***Interestingly, though research has shown that isometric action is
controlled by different brain mechanisms from dynamic action, no such
difference has been found between concentric and eccentric muscle action (we
discuss this point in Ch 1 of “Supertraining”). During all forms of JOINT
action, the underlying process of muscle CONTRACTION is the same, though
there are differences in the utilisation of deformable passive tissues and
the various reflexes.

I can anticipate your possibly detouring into some lengthy semantic arguments
about what we are discussing, and that will simply induce me to summarise
even more information on this topic from some very competent authorities.
So, to fill the gaps in your interpretation of muscle structure and function,
first please read the summaries of current muscle research such as that in
“Supertraining” (1999, pages 38-39) and go to the references cited. Other
relevant texts are:

Fung Y Biomechanics: Mechanical Properties of Living Tissue 1981
Frankel V & Nordin M Basic Biomechanics of the Skeletal System 1980

Scientific American has also featured more recent work on this topic, plus a
Medline search will also yield a huge amount of useful information.

Mel Siff
Denver, USA

.Dr Mel Siff and a Supertraining Yahoogroup member going back and forth

<If you hit bounce off the box correctly you will not experience any problems
with the lower back. The bounce needs to be make on the hamstrings and not
directly with your butt. If you perform it correctly you will the hamstrings
and to some extent the gluts will absorb the impact.

If you perform it incorrectly, you will experience some pressure in the
spine. Sitting back on the box places a lot of pressure on the lower back.
If you perform the bounce correctly, this is no more loading on the
spine…maybe even less that sitting back on the box. >

*** It certainly is useful advice to make most of the contact with the back
of the thighs rather than ever sitting with any significant pressure on the
glutes. However, cases have occurred where poorly understood and
technically hazardous bouncing off a box has caused fractures of area such as
the lumbosacral region of the lower spine, while back pain is also not
uncommon among those who use a definite bounce — and that is the problem
with novice users of the box squat. One cannot emphasize Kenny’s advice
strongly enough that the exercise be done with a correct, very light touching
bounce which does not longitudinally impose impact along the spinal column or
cause the spine to lose its lumbar concavity

Remember that the act of sitting down tends to elicit a relaxation of the
lumbar spine and posterior tilting of the pelvis, which leads to flattening
of the lumbar concavity. If you sit down on a box, you have to make very
definite actions to prevent these spinal relaxing processes from happening,
as is constantly stressed by the Westsiders.

<Bouncing off the box provides a greater stretch reflex. Minimize the risk
by performing it correctly and you’ll illicit a greater training effect in
the stretch reflex.

*** Bouncing off the prestretched muscle complex stimulates the myotatic
stretch reflex more strongly if you do not sit on a box at all. Any
superficial contact with the skin that you sit on will tend to diminish the
intensity of this reflex, plus any delay incurred while you are sitting (even
for less than a second) will diminish it further. Advocates of the box
squat do not even advocate “bouncing” off the box, especially under heavy
loading with a weight or a weight and bands combination.

If you wish to retain enough of the stretch reflex in the muscles of the
“posterior chain”, you should not use the box to offer anything more than a
slight brief touch to the backs of the thighs to enhance proprioceptive
awareness of the position at which you wish to commence your upward drive.
You can gain a good awareness of the prestretch in that position by using a
“Romanian” deadlift — i.e., by lowering and raising the bar from upper thigh
to below the knees by pushing your rear end backwards. Bent-knee good
mornings with glutes thrust back (rather than relying solely on hip flexion
or simple “leaning forwards”) will also enhance one’s awareness of that same
prestretch process.

<You should ease into ballistic box squatting. Once you learn to do it
you’ll illicit a greater training effect in the stretch reflex.>

*** See above – ballistic box squatting will not elicit a greater “training
effect in the stretch reflex”. If you are using box squats to enhance
performance in the squat, the reason is not mainly because you are trying to
“train” the stretch reflex, especially since the competition squat has to be
done without a box and methods of acquiring specific neural programmes tend
to be rather specific to the way in which they were learned. Anyway, I am
sure that this is what Kenny is advising – namely not using the box to sit
upon, but to serve as just a gentle warning system to offer tactile contact
so that you know exactly when to begin your upward drive in the squat. In
this way, you will retain the necessary prestretch and manage to execute the
movement explosively.

There are several reasons why one may use some forms of box squatting, but
“training the stretch reflex” is not one of them. However, the main problem
here is more a matter of scientific correctness and differences in phrasing
the advice more accurately. Some of the box squatting and Westside fans out
there might like to list some of their reasons for using box squats with and
without the added effect of bands for those who have never used box squats.

Mel Siff

For newcomers, these P&Ps are Propositions, not facts or dogmatic
proclamations. They are intended to stimulate interaction among users
working in different fields, to re-examine traditional concepts, foster
distance education, question our beliefs and suggest new lines of research
or approaches to training. We look forward to responses from anyone who has
views or relevant information on the topics.

PUZZLE & PARADOX 72

The effects of joint manipulation or mobilisation may not be as clearly
related to traditional explanations of their underlying mechanisms as
suggested by various therapists.

Most sports scientists, physiotherapists and athletes are very aware of the
various classes of mechanical ‘realignment’ of joints (including
manipulation and mobilisation) that are applied by physical therapists or
chiropractors. These twists, thrust, pulls or pushes of the spinal column,
in particular, are often accompanied by an audible ‘click’ or ‘pop’.

The professional therapists who apply this form of treatment attribute any
subsequent relief from pain or mobility symptoms to processes such as the
reduction of subluxations, stretching of connective tissue, the release of
nitrogen bubbles within the joint fluids, the realignment of joint surfaces,
nerve release and so forth.

This type of procedure is the central foundation of chiropractic and to
manipulative therapy in physiotherapy, with its users totally committed to
its effectiveness. Some long-term studies, however, indicate that joint
manipulation or mobilisation makes no statistically significant difference to
the rate or degree of recovery of the client from pain or malfunction. In
some cases, these procedures have resulted in far greater damage to the
patient, with periodic reports of hemiplegia, quadriplegia or exacerbation
of existing spinal damage appearing (frequently a result of inadequate
collaboration with medical, radiographic or surgical experts).

While the controversy between the merits and demerits of manipulative
procedures will no doubt continue to rage, this is not the main thrust of
this P&P. What appears to remain uncertain is the reason why these
procedures are successful in certain instances. All of the reasons
mentioned above need to be examined carefully before we can state
scientifically that there is a cause-effect relationship between any of them
and rehabilitation from back pain and/or dysfunction.

For instance, let us examine the contention that a quick, sharp thrust of
certain vertebrae will stretch the ligaments in that region and produce
greater mobility at that level. This presumes that a rapid movement will
cause permanent plastic deformation of the connective tissue, which happens
to be viscoelastic in nature. This means that rapid thrusts should evoke a
more elastic response from the appropriate vertebral ligaments, rather than
plastic deformation, which usually is a result of prolonged stretching above
a certain threshold level of strain in the tissues. So, if plastic
deformation is unlikely, this leaves only one other alternative, namely
tissue rupture, which is the last thing that any therapist wants.

However, all of this presumes that the therapist can produce sufficient
manual force to deform ligamentous tissue, which is highly unlikely, because
of its enormous mechanical tensile strength.

This immediately leads us to the hypothesis that many ‘back problems’ are
due to subluxations (small dislocations) of the vertebrae relative to one
another. We immediately have to ask if normal daily activities can
temporarily stretch enormously strong ligaments sufficiently to permit these
subluxations to persist for prolonged periods until the therapist
intervenes.

We have to examine the proof for the existence of these temporary
subluxations such as MRIs or CAT scans – is there unequivocal evidence to
show that ligaments (which are extremely inextensible) can be temporarily
stretched to allow adjacent vertebrae to stay dislocated relative to one
another? If so, then it will be interesting to carry out a biomechanical
analysis of the stresses and strains involved. It will be even more
interesting to understand how the slightly, but powerfully stretched,
ligaments manage to return to their original length along an hysteresis path
that shows no residual strain after prolonged stretching.

Even if one suggests that the subluxation or displacement that is reduced by
manipulation is the sum of tiny contributions from many vertebrae, it does
not eliminate the fact that ligament is very difficult to deform, especially
if subjected to a single sharp thrust.

What then of traction, that is probably used as widely as manipulation? Can
one state that traction stretches ligaments as well and relieves pressure on
nerves? Or is the idea of traction simply to overcome a persistent myotatic
stretch reflex which has temporarily forgotten to become inoperative or a
Golgi tendon reflex that has omitted becoming involved?

Possibly this would then offer a more rational approach to explain why
manipulation might relieve back pain or dysfunction. Such an hypothesis
would suggest that the muscles cause the ligaments to be pulled in a certain
direction, thereby producing and sustaining a subluxation. Of course, we
then have to examine how long a stretch reflex can remain operative and how
long a muscle can remain submaximally contracted. In the case of some back
pain sufferers, we might have to wonder at the impressive local muscle
endurance involved.

There are several other questions remaining regarding manipulation, such as
the cause of the ‘pop’ or click’. If it is indeed produced by the release
of air or nitrogen bubbles into the joints, then this would imply the
occurrence of cavitation, which is known to produce very detrimental shock
waves in engineering systems. If gas bubbles are released in the
cerebrospinal fluid, does this not imply the possibility of micro-shock wave
damage to structures in the spine, especially if manipulation is applied
regularly? Is there any evidence for the release of gas bubbles with
manipulation and, if so, are there any studies to show that they are
harmless artifacts?

Maybe the acute relief afforded in certain cases is more a consequence of
neural stimulation rather than mechanical realignment, caused by stimulation
of the nerves passing from the foramina of the spine. Would this also be a
reasonable hypothesis? Naturally, this would give us the opportunity of
invoking the ubiquitous placebo effect!

This P&P could be extended into the broader territory of deep transverse
friction, structural integration (‘Rolfing’) and so on to create a broader
base for examining the mechanical manipulation of the entire musculoskeletal
system. Indeed, this would probably be of enormous value in removing some
of the controversy associated with all of these procedures.

Comment on any of the issues raised by the above focus on manipulation and
mobilisation as currently practised by various therapists, quoting any
scientific studies which appear to support or disprove the value of these
procedures and the explanations presently given to validate them. Regarding
the mechanisms involved – Is it in the back or is it all in the head?

——————

Mel Siff

Here is an interesting paper which investigates that old problem of the
sticking point in the bench press. However, the same analysis is also
relevant to the sticking point in any other non-ballistic movements.

Note the conclusion that the sticking region does not appear to be caused by
worse leverage (“an increase in the moment arm of the weight about the
shoulder or elbow joints”) or by a significant decrease in muscle activity
during this region. The authors suggest that the problem may lie in the
possibility that the sticking region represents a force-reduced transition
zone between the earlier stretch-assisted acceleration-strength phase and the
later mechanically efficient maximum strength region. The use of limited
range elastic band and chain training (e.g. by Louie Simmons and the Westside
team) may play a useful role in attending to this specific deficit in the
transition zone referred to in this paper.

The relevance of analysing the force-time curve in terms of strength
qualities such as starting strength, acceleration-strength, maximal strength,
explosive strength then becomes more obvious, as discussed in Ch 2 of
“Supertraining”. A better understanding of these fundamental biomechanical
factors then enables one to plan one’s training more effectively.

————————

Elliott BC, Wilson GJ, Kerr GK.

A biomechanical analysis of the sticking region in the Bench Press

Medicine & Science in Sports & Exercise. 21(4):450-62, Aug 1989.

The performance of ten elite powerlifters were analyzed in a simulated
competition environment using three-dimensional cinematography and surface
electromyography while bench pressing approximately 80% of maximum, a maximal
load, and an unsuccessful supramaximal attempt.

The resultant moment arm (from the sagittal and transverse planes) of the
weight about the shoulder axis decreased throughout the upward movement of
the bar. The resultant moment arm of the weight about the elbow axis
decreased throughout the initial portion of the ascent of the bar, recording
a minimum value during the sticking region, and subsequently increased
throughout the remainder of the ascent of the bar.

The electromyograms produced by the prime mover muscles (sternal portion of
pectoralis major, anterior deltoid, long head of triceps brachii) achieved
maximal activation at the beginning of the ascent phase of the lift and
maintained this level essentially unchanged throughout the upward movement of
the bar.

The sticking region, therefore, did not appear to be caused by an increase in
the moment arm of the weight about the shoulder or elbow joints or by a
minimization of muscular activity during this region.

A possible mechanism which envisages the sticking region as a force-reduced
transition phase between a strain energy-assisted *acceleration phase* and a
mechanically advantageous *maximum strength* region is postulated.

—————-

Mel Siff