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

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

Almost all of the comments that one reads about the wearing of supportive
lifting apparel, wraps and belts are negative, with admonitions that use of
these compressive or supportive aids creates some sort of dependence and loss
of strength. Previously I have discussed their positive role in enhancing
proprioceptive awareness and helping an athlete train when sore or injured
(e.g. in my “Facts & Fallacies of Fitness” book), but let us now investigate
this issue further with the assistance of the following reference.

The study below shows that even moderate resistance training executed while a
muscle is compressed can produce a greater increase in strength, hypertrophy
and local muscle endurance than if one trains without the muscle being
compressed. Note that the exercise was performed with only 50% of 1RM and
that the compression only amounted to less than one-third of atmospheric
pressure, so it would be interesting to see how the results would change with
greater resistance and somewhat greater levels of compression.

Let us now recall the typical loading used in explosive lifting training
(i.e. with loads of 50-67% of 1RM), which is of the same order of magnitude
as was used in this experiment. Suppose, instead of not wearing supportive
garb, we chose to train regularly with firm wraps, powerlifting suits/vests
or neoprene sleeves. Would this not possibly result in increases in strength
and all those other performance factors?

Maybe all that theoretical advice that supportive apparel is detrimental to
training might be proved to be very wrong indeed — after all, the evidence
quoted is based entirely on theoretical grounds and anecdotes, while the
below study proved experimentally that compression-aided training improves
several fitness and strength qualities of high-level athletes. Maybe wearing
a belt not only enhances proprioceptive sensitivity, confidence and some
“core” stability, but it actually may increase the strength and growth of the
trunk musculature. Similarly, wraps around the thighs, chest and arms may
produce the same effects in those regions. What then about doing
crunches and other abdominal exercises while wearing wraps or a very flexible
corset around the trunk?

Only one way to find out about this theory without waiting for scientists to
take many months and a few years to have their research published – we can
personally try this (moderate) compression training method for a few months
and see what happens. There is nothing to lose and something to gain. We
could try squatting or cleaning with wraps (or neoprene sleeves) around the
thighs and bench pressing with lifting shirt and wraps around the upper arms
- and keep careful records of lifts and limb girths (and skinfolds) to
monitor any changes (and compare them with our usual patterns of change).

Now read the study for yourselves:

—————-

Effects of resistance exercise combined with vascular occlusion on muscle
function in athletes

Yudai Takarada, Yoshiaki Sato & Naokata Ishii

Eur J Appl Physiol (2002) 86: 308-314

The effects of resistance exercise combined with vascular occlusion on muscle
function were investigated in highly trained athletes. Elite rugby players
(n=17) took part in an 8 week study of exercise training of the knee extensor
muscles, in which low-intensity [about 50% of one repetition maximum]
exercise combined with an occlusion pressure of about 200 mmHg (LIO, n=6),
low-intensity exercise without the occlusion (LI, n=6), and no exercise
training (untrained control, n=5) were included. The exercise in the LI
[non-compression] group was of the same intensity and amount as in the LIO
[compression - MCS] group.

1. The LIO [compression] group showed a significantly larger increase in
isokinetic knee extension torque than that in the other two groups at all the
velocities studied.

2. On the other hand, no significant difference was seen between LI
[non-compression] and the control group.

3. In the LIO [compression] group, the cross-sectional area of knee
extensors increased significantly, suggesting that the increase in knee
extension strength was mainly caused by muscle hypertrophy.

4. The dynamic endurance of knee extensors estimated from the decreases in
mechanical work production and peak force after 50 repeated concentric
contractions was also improved after LIO [compression], whereas no
significant change was observed in the LI [non-compression] and control
groups.

The results indicated that low-intensity resistance exercise causes, in
almost fully trained athletes, increases in muscle size, strength and
endurance, when combined with vascular occlusion [compression].

————-

Mel Siff

On the Yahoo Supertraining group, a subscriber relayed the following story:
<I recently attended an NSCA seminar on Speed, where one of the presenters
(Ted Keating PhD) mentioned a “new” type of muscle contraction (at least new
to me). It is called an ECCONCENTRIC muscle contraction, where one part of
the muscle is shortening and the other is lengthening. The title of his
presentation was “Sprint Biomechanics”.

For example: shoulder flexion with elbow extension, where one part of the
bicep is shortening (as in shoulder
flexion) and the other part is lengthening (as in elbow extension).

Have you heard of this before? Does it go by another name? And is it good to
train certain muscles using
that principle (maybe hamstrings?). The lecturer provided no references for
his remarks. >
Mel Siff responded with the following;
*** First of all, many scientists today prefer not to refer to muscle
“contraction” and instead use the word, “action”, to minimise any of the
existing confusion about “lengthening” of muscle during eccentric action and
to eliminate the need for creation of any new such words or ideas such as
what you have just mentioned. Anyhow, what you described happens very
commonly with any muscles that cross more than one joint. Many jumps,
throws, “plyometric” drills, the so-called “double knee-bend” in the Olympic
pull, and other ballistic movements automatically invoke this sort of action,
so there is no need to do anything special to make use of it.

The speaker more accurately should have referred to one joint angle
increasing and another decreasing during the movements that he was
addressing, as is conventional for any kinesiological analysis of
bi-articular (two jointed) muscle action. It is misleading to imply that
one end of a muscle is lengthening while its other end is shortening. That
sort of curious event does not happen in a uniform, continuous elastic band
and it does not happen in a continuous muscle.

The ability of some muscles to activate locally (some work has been done in
this regard with respect to the deltoids) does not depend on local
lengthening or shortening, but as a consequence of neural excitation.
However, the act of flexing the shoulder, e.g., in a “biceps curl”, can
prestretch the elbow flexors and produce greater force at some stages of the
exercise. There is absolutely no need to use that term “ecconcentric muscle
contraction” because the entire biceps group of muscles (and some other elbow
flexors) is in concentric (or “overcoming”, as the Russians would call it)
action during that exercise. There is no such “new” type of muscle action
called ecconcentric.

Many years ago, some scientists vainly attempted to resolve all this
confusion and dissatisfaction with existing terminology by creating these
definitions:

- isometric (no external joint action evident)
- pliometric ( “eccentric” action)
- miometric (“concentric” action)

What happened? Well, someone decided that the Russians (as usual, those
crafty bearers of all the training secrets in the world!) were using a
special type of training which looked like it relied mainly on “pliometric”
action – the person/s concerned misspelled the word in the form of
“plyometrics” and that label has stuck so well that the original Russian
concept upon which it was based, namely shock method (udarniye metod), has
largely fallen into disuse in the West.

It would be preferable if that speaker and all others in future simplified
the whole muscle mechanics issue by talking about “muscle action” and dropped
all reference to contraction, ecconcentrics and any other such confounding
terminology — or at least placed inverted commas about those terms to remind
us of their limitations.

Mel Siff