The following resources were cited on the Biomechanics list as useful ones
for supplying useful information on soccer biomechanics, in particular the
action of kicking. Would anyone care to add other references on this topic?

Anderson DI & Sidaway B. (1994) Coordination changes associated with practice
of a soccer kick. Res Q Exerc Sport, 65, (2): 93-9

Barfield WR. (1998) The biomechanics of kicking in soccer. Clin Sports Med,
17 (4):711-28

Davids K, Lees A, Burwitz L. (2000) Understanding and measuring coordination
and control in kicking skills in soccer: implications for talent
identification and skill acquisition. J Sports Sci, 18 (9): 703-14

Lees A, Nolan L. (1998) The biomechanics of soccer: a review. J Sports Sci,
16,(3):211-34

Levanon J, Dapena J. (1998) Comparison of the kinematics of the full-instep
and pass kicks in soccer. Med Sci Sports Exerc, 30 (6): 917-27

Teixeira LA. (1999) Kinematics of kicking as a function of different sources
of constraint on accuracy. Percept Mot Skills, 88 (3 Pt 1): 785-9

Dr Mel Siff
Denver, USA
http://groups.yahoo.com/group/Supertraining/

A member wrote wrote:

< …..I think this BOX SQUAT exploration is interesting and assume (excuse
the pun if you see it) that most have not analyzed it completely.

There are many reasons that those who use this squat are able to handle such
enormous weights. I mentioned that I thought the action/reaction sequence of
the compression and expansion of the hams and gluteals against the unyielding
surface of the box was more of a factor than most perceived at the very start
of the action forwards and upwards.>

Dr Mel Siff: You may recall that we both discussed this issue some months ago on this
list, when I also stressed that the contact between adjacent soft tissue
surfaces can play a useful proprioceptive facilitation role. The box squatting
action
concerns not simply the hams and glutes, because the compression-expansion here
tends to
be more viscous and damping in nature than elastic (the contact time often is
too long
to permit significant elastic energy recovery and the mechanical stiffness of
the
posterior chain muscle complexes is too low in that situation) — there can be
an even more powerful contribution between the lower abdomen and the top of
the thighs, where pneumo-elastic recoil can be quite marked.

Member:

<I have also suggested that the “lever arm” of the femur is “in contact” with
the box at a shortened and more effective leverage position during the
initial “push off” stage. This too is a substantial contributor to being
able to handle “larger” loads. An example might be if you imagine squatting
by holding the bar (in your hands) on your thigh at “hip joint” level. Then
imagine squatting again, but this time moving the bar down to just above your
knee. Which squat would be easier? In the box squat, the initial leverage
is more favorable.

Dr Mel Siff:  This is not a valid analogy – by moving the bar as you have described it,
you have changed the centre of mass of the combined bar-lifter system, not
simply shifted the fulcrum. For all list members who like challenges, try
drawing a “free body diagram” and see what that tells you about any comparison
between squatting in free space and squatting on a box. For anyone who would
like to carry out this biomechanics tutorial, go ahead and let me have your
feedback, if necessary sending me a JPG or PDF file of your resulting diagrams.

Dr Mel Siff
Denver, USA
http://groups.yahoo.com/group/Supertraining/

The following article discusses the correlations between the Olympic lifts
and various tests of physical structure and function. Note that there is a
high correlation between Weightlifting Performance in both lifts and HEIGHT
of the pull during the snatch and the clean — this relates to the discussion
on lifting pulling techniques that we are also analysing at the moment.

———————–

Predictive Value of Physical Development Tests, Physical and Technical
Preparedness on the Structural-Functional State of Weightlifters in the
Pre-Competition Period

Yasyunas VA & Gailyunene AV

[Some extracts appear below -- see the full article in the 1982 Russian
Weightlifting Yearbook translated by Bud Charniga at www.dynamic-eleiko.com]

The rapid growth of results in weightlifting is the result of many factors.
The most important role here is the constant improvement in training methods.

The perfecting of training methods is manifested by the increased volume of
the training means, the increase in the volume and intensity of the training
loads and the control of the athlete’s state (physical, technical,
functional). Control of the individual aspects of the athlete’s preparedness
requires special attention.

It is known that the given controls serve as the objective basis for planning
the training loads (Vorobyev, 1971; Zatsiorsky, 1979). In conjunction with
the influence that the different training methods have on the body’s organs
and systems, the athlete’s strength, speed or endurance improve. This rise in
work capacity is displayed in the form of structural and functional
adaptation. Direct or indirect changes in adaptive response enable one to
draw conclusions about the physiological effect of training and help to
determine the athlete’s state of trainability.

Programmed tests are repeatedly criticized because competition achievements
(or training) do not always coincide with test results. However, the
generalized assessments of a complex of tests, correlated with adequate loads
helps to yield an objective assessment concerning the state of trainability
at a given time. The use of these tests can be of great assistance to the
trainer in determining the effectiveness and the detection of deficits in
training and contribute to more rational training methods.

Moroz (1951), Vorobyev (1964-1971), Roman (1965), Sokolov (1970), Chernyak
(1967-1971), Ippolitov (1975), Oleshko (1980) and other authors have
attempted to determine weightlifters’ level of physical and technical
preparedness. However, the specialised literature indicates that these and
other authors used many different tests and their data was collected under
the most diverse conditions. Therefore, it is difficult to compare the data
obtained by the different authors.

Our purpose was to find the most informative tests for determining the level
of physical development, physical and technical preparedness, and the
structural-functional state of weightlifters in the pre-competition period.

Twenty-six weightlifters ages 16-26 of which 16 were Masters of Sport (group
A) and 10 were class I and candidates for Master of Sport (group B) took part
in the study.

The following tests and measurements were used to test the weightlifters’
physical and technical preparedness: vertical jump (V M Abalakov’s method),
vertical jump with 25% and 50% of the subject’s bodyweight on the shoulders,
standing long jump, 5 consecutive standing long jumps, 30 meter sprint from a
walking start, standing and hand dynomometer tests, best snatch and the clean
and jerk, height of the lift for snatch and clean pulls, back squat, static
pull and its ratio to best snatch and best clean and jerk and the criteria of
technical preparedness (Chernyak, 1978).

Considering the fact that the structural-functional criteria of physical
development assessments in weightlifting play an important role not only for
sport selection and orientation, but for the diagnosis and prognosis of sport
mastery, for determining models and standard characteristics and for the
assessment of trainability growth we studied the following indicators: Bruksh
index (%), Erisman index (cm), Vital index (ml/kg), ratio of height to the
length of the lower extremities, Pine index, Adiposity index (kg/m^2), body
surface area (sq m), body length (cm), body mass, bone and muscle tissue (in
kg and % respectively), combined sum of bone and muscle mass (kg); heart
rate, blood pressure and other indices (Kozlov & Gladysheva, 1977; Aulik,
1979; Jackson & Pollock, 1977 and others).

However, not all of the indices studied were of equivalent significance for
diagnosis and prognosis.

From the data in Table 1 it can be seen that there is a statistically
significant correlation for Masters of Sport and Class I athletes with the
maximum snatch in the 16 indices studied.

The highest correlation (r > 0.8) in both groups was between maximum snatch,
back squat, body mass, Pine index, active body mass, height of the lift in
the snatch and height of the lift in the clean.

A statistically significant correlation was obtained (Table 2) with the
maximum clean and jerk and 17 indices for the Masters of Sport and with 11
indices for the class I athletes.

The highest correlation (r > 0.8) in group ‘A’ was between the maximum clean
and jerk and the back squat, body mass, active body mass, combined sum of
bone and muscle mass and height of the lift in the clean.

The highest correlation in group ‘B’ was between the maximum clean and jerk
and grip strength, body mass, height of the lift in both the snatch and the
clean and jerk.

The data indicates that there is a high negative correlation between certain
tests and achievements in the competition exercises. It has been shown that
the most informative indices for determining physical development in the
pre-competition period are the following:

Group A

1. Grip strength
2. Thigh Extension Strength
3. Body mass
4. Pine index
5. Standing Dynamometer strength

Group B

1. Grip strength
2. Torso strength
3. Body mass
4. Body height (length)

Indices of Physical Preparedness

Group A

1. Back Squat

Group B

1. Five consecutive standing long jumps
2. Standing long jump

The structural states of weightlifters in the pre-competition period are best
characterized by the following indicators: body mass, active body mass,
combined sum of bone and muscle mass, body surface area and absolute muscle
tissue mass.

Indices of Technical Preparedness

Group A

1. Height of the lift in the snatch
2. Height of the lift in the snatch pull
3. Height of the lift in the clean
4. Height of the lift in the clean pull
5. Criteria of technical preparedness in the snatch

Group B

1. Height of the lift in snatch pull
2. Height of the lift in the clean pull
3. Height of the lift in the clean
4. Criteria of technical preparedness in the snatch

Table 1 Correlation between Maximum Snatch and Test Results for Weightlifters
of Various Qualification

Master of Sport Test Indices Correlation coefficient r

1. Grip strength 0.598
2. Thigh extension strength 0.784
3. Back squat 0.804
4. Static pull 0.733
5. Body mass 0.805
6. Pine index 0.804
7. Adipose index 0.738
8. Body surface area 0.674
9. Bone tissue, absolute mass 0.618
10. Muscle tissue, absolute mass 0.760
11. Active body mass 0.806
12. Combined sum of bone and muscle tissue 0.773
13. Height of the lift in snatch pull 0.694
14. Height of the lift in the snatch 0.845
15. Height of the lift in the clean 0.845
16. Criteria of technical preparedness in snatch 0.714

Table 1 continued

Candidate for Master of Sport and Class I Lifters

Test Indices Correlation coefficient, r

1. Standing long jump 0.705
2. Five consecutive standing long jumps 0.724
3. Grip strength 0.762
4. Back squat 0.609
5. Torso strength 0.606
6. Body mass 0.794
7. Body length 0.710
8. Bone tissue, absolute mass 0.563
9. Muscle tissue, absolute mass 0.792
10. Active Body mass (kg) 0.820
11. Combined sum of bone and muscle masses 0.791
12. Height of the lift in snatch pull 0.715
13. Height of the lift in clean pull 0.795
14. Height of the lift in the snatch 0.879
15. Height of the lift in the clean 0.872
16. Criteria of technical preparedness in snatch 0.861

Table 2 Correlation between Maximum Clean & Jerk and Test Results

Master of Sport Test Indices Correlation coefficient, r

1. Grip strength 0.702
2. Thigh extension strength 0.729
3. Back squat 0.813
4. Static pull 0.757
5. Body mass 0.849
6. Pine index -0.821
7. Adipose index 0.733
8. Body surface area 0.732
9. Bone tissue, absolute mass -0.573
10. Muscle tissue, absolute mass 0.777
11. Active mass of the body 0.843
12. Combined sum of bone and muscle tissue 0.804
13. Height of the lift in snatch pull 0.621
14. Height of the lift in clean pull 0.637
15. Height of the lift in the snatch 0.849
16. Height of the lift in the clean 0.899
17. Criteria of technical preparedness in snatch 0.779

Table 2 continued

Candidate for Master of Sport and Class I Lifters

Test Indices Correlation Coefficient, r

1. Five consecutive standing long jumps 0.689
2. Grip strength 0.820
3. Back squat 0.759
4. Static pull 0.762
5. Body mass 0.800
6. Pine index -0.658
7. Muscle tissue, absolute mass 0.735
8. Active mass of the body 0.717
9. Combined sum of bone-muscle tissue 0.780
10. Height of the lift in the snatch 0.800
11. Height of the lift in the clean 0.854

Dr Mel Siff
Denver, USA
http://groups.yahoo.com/group/Supertraining/

You may recall my referring before to Dr Tom McLaughlin’s book on the
biomechanics of bench pressing (“Bench Press More Now”) — well, here is an
interesting paper that he and a colleague wrote on the biomechanical
differences between novice and expert bench pressers.

————————

Madsen N, McLaughlin T

Kinematic factors influencing performance and injury risk in the bench press
exercise

Med & Science in Sports & Exercise. 16(4):376-81, Aug 1984.

The purpose of this research was to identify kinematic factors that could be
relevant to performance and injury risk in the bench press. The methods used
included: use of high-speed, 2D cinematographic procedures to record the
performances of 36 subjects (19 experts and 17 novices), determination of the
kinematic and kinetic differences between the groups, and identification of a
rationale describing how those kinematic differences could lead to the
kinetic differences. Kinematic factors so identified could influence
performance and injury risk.

In addition to the fact that experts were able to lift 79% more weight than
the novices, the pertinent KINETIC DIFFERENCES included the following:

1. the difference in peak force exerted while lowering the bar was only 43%;
2. the difference in peak force exerted while raising the bar was only 45%;
3. the difference in minimum force exerted while raising the bar was 87%.

There was no significant difference in torque required at the shoulder.

The relevant KINEMATIC DIFFERENCES were:

1. the expert group maintained a smaller bar speed while lowering the bar,
2. the expert group used a bar path closer to the shoulders; and
3. the expert group used a different sequence of bar movements.

The roles of these kinematic factors in the bench press merit further
investigation.

[It would be interesting to compare above finding No 2 with the Westside
recommendation to follow a lower trajectory than one that is closer to
the shoulders. Comments on all the above findings would also be of great
interest to many. Mel Siff]

Dr Mel Siff
Denver, USA
http://groups.yahoo.com/group/Supertraining/

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

<<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

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

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

<< 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

*** 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