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
8) >>
***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
Denver, USA
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