Dr Mel Siff Blog

Recently we discussed the proliferation of some very dubious and incorrect
biomechanics in various journal articles. A book that is quite often
recommended by the Cooper Institute and other fitness organisations for
personal trainers is “Muscle Mechanics” (Aaberg E Human Kinetics 1998)
contains the following further gems of pseudo biomechanics. My comments
below these extracts serve as a partial book review.

<<1. To perform resistance training, there must first be a
resistance….Some may visualize dumbbells, barbells and metal plates.
Others may think more of pulleys, cables and machines. Though different,
these are all weights with gravity providing the actual resistance. (page 7)
>>

*** The idea that gravity somehow provides some sort of invisible resistance
is rife in the fitness world. It is clear that many fitness lecturers do not
know what is meant by “gravity” and certainly do not know the difference
between “inertial force”, “gravitational force”, “weight” and “mass”. They
need to know that a massive object exerts a force known as “gravitational
force” on another massive object by virtue of the two masses involved,
according to the equation:

Force F = GMm/R^2 (or G*M*m divided by R squared)

where G is the ‘gravitational constant’, M and m are the masses of the bodies
attracting one another via gravity and R is the distance separating the
bodies.

On the surface of the Earth, the gravitational force tends to accelerate a
body on its surface with an acceleration of g (about 9.8 metres per second
squared). Gravity does not “provide the actual resistance” – the mass of the
Earth produces a gravitational acceleration that acts on the weight that we
are lifting (and vice versa), thereby producing what is known as the “weight”
of the mass or load at that specific location on the Earth.

If we are to be pedantic, the weight of a given load is less at the poles
than the equator, since the radius R of the earth is greater at the equator
than the poles. It is very misleading and totally incorrect to even
popularise gravity as being some sort of “resistance”. That is way off
course.

<<2. Dynamic Constant Resistance. In this type of training, the resistance
used is constant. The most common examples of this would be free weights and
certain machines that use only round pulleys or rollers to redirect the
resistance, but they do not alter the resistance during exercise. (page 7) >>

***Machine manufacturers have been using this faulty reasoning to promote
their ‘variable resistance’ products for many years. The fact is that, while
the mass or load on the bar or machine may be constant, the resistance
offered to the exerciser depends on the acceleration of the load. Skilled
trainees even alter this resistance voluntarily by using the method of CAT
(Compensatory Acceleration Training). Weights are NOT constant resistance
training devices; they are constant MASS devices.

<<3. Isokinetic Resistance. Isokinetics refers to the contraction of a
muscle performed at a constant angular velocity. This means that the speed
at which the muscle lengthens and shortens is constant, but not necessarily
the resistance. The motion cannot be accelerated. Any force applied in an
attempt to increase velocity results in an equal reaction force. These
opposing forces will mirror each other throughout the range of motion. (page
>>

***First of all, all physiology texts state that a muscle can only contract
or relax, but never lengthen. (note very well we are not talking about
possible lengthening of the muscle COMPLEX which contains collagenous
elements such as tendons, which can lengthen under certain conditions). This
point is made in Physiology 101 or even in high school biology courses.

Besides the fact that the author regularly interchanges speed and velocity,
there are several other errors in his understanding of isokinetics – would
others care to analyse them for fun?

<<4. …what many people call a dumbbell arm curl shall be listed as a
dumbbell biceps flexion or dumbbell biceps flex.” (page 6) >>

*** This suggests that elbow flexion is carried out exclusively by the
brachial biceps. This is not even vaguely acceptable, because elbow flexion
is associated with action of the biceps, brachialis and brachioradialis.
Moreover, the use of terms such as flex or flexion in functional anatomy
refers to joints not muscles.

<<5. Yet another possibility is that a muscle could be contracting
isometrically while it neither shortens nor lengthens. >>

*** It is also a very common misconception that an isometric muscle action is
not associated with muscle contraction or shortening. While an isometric
action produces no external movement of the joint, the muscle is very
definitely is contracting within the body.

<<6. ..A degree of force angle must be present before a muscle can have much
biomechanical advantage in performing any loaded joint motion. Therefore, it
is important not to fully extend or lock any joint during resistance-training
exercises. (page 40) >>

*** One might ask how one should execute many of the weightlifting and
powerlifting exercises and their numerous variations if one should not lock
the joints? This belief has been around the aerobics floor for many years
and it is most surprising that some ‘experts’ still believe it. As a simple
example, try ordinary walking without locking the knee, in particular – it
looks and feels hilarious. I, for one, would also be terrified of snatching
with my elbows and shoulders unlocked at the end of the movement!. There
is much more room for further comment here – any offers?

<<7. For most people, conducting singular-plane joint movements is
preferable to multiple-plane joint movements with most resistance-training
exercises. The reasoning for this goes back to the same two principles this
book is based on – efficiency and safety. >>

*** Just an opening comment about terminology – there is no such entity as
“singular-plane” – the recognised term is “single-plane” or “uniplanar”.
The author regularly misquotes standard terminology like that, but I have not
focused on this, because these minor transgressions merely serve to act as
pointers that the author is not very conversant with working in the field of
biomechanics and functional anatomy.

I would like others to comment on the main point in this quotation, since it
has some major implications for all resistance training. At the very least,
we must stress that multiple joint, multiple plane action tends to be more
efficient and often less stressful on the joints than uniplanar, isolated
joint action. Even many physical therapists are now acknowledging this fact
by advocating “closed chain” e.g. free standing squats) instead of “open
chain” exercises (e.g. seated ‘knee extensions’).

Even though the title of the book is “Muscle Mechanics” and the first chapter
is called “The Principles of Muscle Mechanics” , there is not a single
paragraph or sketch explaining the mechanics of muscle action, nor a single
sentence about the relationship between muscle mechanics and strength,
hypertrophy, flexibility and other fitness qualities. It is clear that the
title was chosen simply for the sound of the term rather than its
relationship to the topic of muscle mechanics.

Most of the book is devoted to illustrations of about 73 different exercises,
many of them using the physio ball and various gym machines. Many of these
exercises are replete with errors and some of them are of dubious safety for
the average person (such as straight leg raises off the end of a bench).
Most fascinating of all is that the entire section on trunk and abdominal
exercise does not even mention any role for the quadratus lumborum and
transversus muscles, something that virtually no other book on trunk training
and stabilisation manages to do.

Other than complimenting the book for being well illustrated and attractively
packaged, no quality-concerned lecturer could advocate the use of this text
as a serious reference for personal trainers, especially since the author
declares that:

“You can easily see how training properly by using ‘Muscle Mechanics’ could
be the most important thing you’ve ever done for the integrity of your body”
(p 4). …..and …..

“Also be sure that the trainer you interview is familiar with the davanced
techniques and exercise specifics presented in this book.” (p 8).

If one is going to extol the virtues of one’s own book in that manner, then
it has to be subjected to special scrutiny to determine the accuracy of those
claims.

There are several free websites that give you far superior training
information than this. Would anyone care to list their favourites here?

Dr Mel C Siff

Recently an article “Toward an Understanding of Power” was written in the
NSCA’s Strength & Conditioning Journal (Oct 1999: 34-35), which contained
some curious biomechanical definitions and calculations. Here are a few of
them for your interest:

1. “For instance, in cleaning a weight, the velocity of the bar is equal to
its speed and the upward direction in which it moves.”

2. “Strength times speed equals power”

3. Work = force x distance, where Force = Mass lifted,
Distance = gravity x height of pull
Gravity = 9.8 m per sec squared

The article then used the above definitions to calculate power and hence
compare the power generated in the Weightlifting clean and the Powerlifting
deadlift, thus:

Power = Work/Time to execute lift

….but did not distinguish at all between mean power, power at any instant
and peak power during the lifts concerned (deadlifts and cleans).

Would anyone else care to comment on the material which I have quoted above?

In a letter to the editor of the journal, I stressed that one cannot casually
equate velocity (a vector) and the speed (a scalar) ,especially in
non-linear dynamic lifts, and that work is not simply Force x Distance in a
system in which force and direction of application of the force is changing
throughout the movement. I also pointed out the obvious errors in equating
Force with Mass and in defining Distance = gravity x height of pull (all of
this is nonsense).

The author of the article simply replied in the Aug 2000 issue of the same
Journal that:

” I had Dr L, chairman of the math/physics department at …….. University,
review the formula along with the comments. Dr L said that my calculations
are correct…… In trying to make the formula more understandable to
people with no background in math and physics, I had added a few extra words
for clarification purposes, which to a purist was not acceptable.”

Would anyone care to comment on this response, as well?

What concerns me is that this NSCA (National Strength & Conditioning Associati
on) publication reaches tens of thousands of its members all around the
world, many of whom do have at least 4 year degrees in physical education,
kinesiology, science, physical therapy and related fields. The NSCA
administrates and awards the CSCS (Certified Strength and Conditioning
Specialist) qualification and Personal Trainer certification. It is widely
regarded as the definitive source of strength training information for
strength coaches and includes many highly qualified scientists in its ranks,
yet it seems quite contented to allow seriously misinterpreted scientific
information to reach its members.

The NSCA is not unique in this regard. Many other certifying bodies and
training organisations in the strength and fitness realm reveal a similar
attitude that their members “are not scientists” and need not be given a
rigorous background to the simplified concepts that are taught to them.

Some lecturers on the popular fitness circuit have casually confused torque,
moments, couples, force-couples and many other standard mechanics
terminology, yet, when I have tried to point out their errors, they have
simply responded with personal attacks. In a different way, the author of
that NSCA article (a prominent strength scientist in the USA and author of
several books) totally refused to accept that his definitions were
incorrect and misleading.

It seems as if many authorities in the fitness and
strength world consider that they never make mistakes and, if they do, they
should never admit them. Their standard method of handling anyone who
comments on their errors is to attack the messenger very emotively and to
totally ignore the incorrectness of the message. And so, the status quo
continues!

While popularisation of difficult concepts is vital for the general public
and some folk, such as the late Carl Sagan were masters at this, are these
organisations and lecturers not doing their members, clients and the
strength/fitness professions a grave disservice? Is there any solution to
this problem?

Dr Mel C Siff

Some years ago I seem to recall an article which concluded that loaded
hyperextension of the spine was potentially less harmful to the lumbar spine
than unloaded hyperextension such as that encountered in throwing and jumping
sports. Possibly someone else can locate that reference. This might explain
why the incidence of hyperextension injuries in Olympic weightlifting appear
to be far less common than in sports such as cricket and gymnastics.

Many have militated against all spinal hyperextension, but they seem to
forget that McKenzie techniques (as variants of the ancient yoga Cobra asana)
actually comprise controlled forced hyperextension of the spine in a posture
which does not allow the lower body to sway and dissipate stress as in the
standing Olympic Press. Sure, we have pointers such as the
peripheralisation or centralisation of pain symptoms to guide us to the
suitability of McKenzie, but why are many folk adamant about avoiding all
forms of hyperextension, irrespective of such guidelines?

Then, we also must distinguish between the strictly controlled hyperextension
of the spine in the sagittal plane during the Olympic Press, compared with
the complex lumbar hyperextension, trunk rotation, lateral pelvic tilting and
asymmetric foot impact actions involved in cricket bowling, tennis serving,
gymnastics and so forth. Are we justified in comparing simple hyperextension
in one plane with complex trunk actions in several planes?

All too often, it seems to be forgotten that even small torque about the
vertebrae can produce more strain in the peripheral annulus of the disk than
far more extensive flexion or extension. This tends to reflect itself in
training and rehabilitation programs drawn up for athletes and workers – the
(often machines-controlled) movements and stretches very rarely involve
significant use of rotatory actions, especially under progressively
increasing conditions of resistance and range. Yet, all physical therapists
have been exposed to the well-known patterns, pacing, procedures and
principles of PNF with all of its emphasis on the regular use of spiral and
diagonal patterns.

This may well explain why the incidence of injuries associated with forceful,
sudden, ballistic or large range rotation of joints may be so rife in sport -
witness for instance, the mainstays of sports therapy with its epidemic of
rotator cuff, ACL and similar injuries. Machine training and even free
weight training seems to concentrate largely on linear or uniplanar actions,
and if rotation is involved in training, it takes place only in the sport
itself or in the gym via the use of gentle yoga-like stretches and warmups.

It is not only exposure to a stressful action that can cause injury, but also
religious avoidance of so-called dangerous actions (which might occur during
actual sporting conditions). One cannot expect the body to cope with the
immense structural and functional demands placed on the body in sport unless
one methodically conditions the body to cope with progressively greater
structural and functional stresses.

Dr Mel C Siff

Dr Mel Siff responders to a members enquiry about Force Plates on the Supertraing List as found at www.yahoogroups.com

<< Re: lab equipment—I use an interface called “Data Studio” to gather,
plot, and analyze data of impulse phenomena involving lab carts, fans, model
rockets, etc. This Pasco apparatus and software quite nicely allows for
variable force graphical analysis to be used with high school freshman long
before they are ready to perform calculus. It allows older students to
confirm their calculations and easily go into areas previously reserved only
for university labs. This system is unable to handle forces the size of
which we speak in training applications.

I assume the force plate apparatus does much the same thing on a larger
scale? An earlier post mentioned a “cheap force plate”. Could someone
inform me if they work similarly to my smaller lab apparatus and how cheap
is cheap? If you could point me in the right direction to find this
information, I would appreciate it. >>

***A force plate or force platform in essence is a sophisticated type of large
bathroom scale which can measure forces in the X, Y and Z directions and the
torque about each of these axes. An athlete carries out typical sporting
actions on this device or runs across it, while the information is fed
through an Analogue to Digital (A-D) card into the computer, where the
required analysis is carried out.

Construction of a relatively inexpensive force plate to measure the forces in
the X, Y and Z directions is not at all beyond the capabilities of the
average competent engineer. All that one needs to do is to construct a
suitable “load cell” using strain gauges secured by means of special epoxy
resin at appropriate locations on the deformable elements of the cell and
install four of them at the corners of a heavy wooden or metal platform. One
has to be sure that the resonant frequency of the platform is nowhere near
the sort of frequency of vibration produced in any activities that you wish
to study.

My Civil Engineering colleague who manufactured them still works at my former
university and still makes a limited number of these force plates, so if you
are interested, you could contact him in South Africa at:

hofmeyr@civen.civil.wits.ac.za

Failing that, you can also buy piezoelectric film that may be placed under a
platform to enable you to measure vertical reaction forces. In fact, you can
place it on any surface to measure forces like that, but remember that it
only gives information in one direction. You need to locate it in a few more
positions if you wish to measure three dimensionally. Remember, too, that
piezoelectric devices do not measure static or isometric forces, but they are
fine for dynamic measurements.

All that you need to do is buy a suitable amplifier (“signal conditioning
unit”) and A-D card for your computer and you have your basic force measuring
device. All of these devices may be found readily via the Web. A
biomechanics colleague of mine, Dr Gideon Ariel, has a great deal of
information on his website about such devices, plus a lot of free software to
help you along. Go to:

http://www.arielnet.com

Students can easily make their own crude force measuring devices with this
sort of film. Quite often, you will see simple force devices (typically for
measuring jumping force or reaction times) being sold for several hundred
dollars by sports performance and machine companies, but they are little more
than devices using such film being sold at a huge profit.

Dr Mel Siff

<< Can you please help me locate websites that explicitly deal with detailed
biomechanics in sports, ie analysis of forces, moments, joint angles, etc…
It doesn’t matter which kind of sports is analysed. >>

*** The following websites will give you plenty of information on all aspects
of biomechanics:

http://www.per.ualberta.ca/biomechanics/bwwnofrm.htm (Biomechanics Worldwide)
http://isb.ri.ccf.org/ (International Society of Biomechanics)

Dr Mel C Siff
Denver, USA