Some of these therapists, especially those with informal or self-awarded
‘credentials’, spend an inordinate amount of time applying an extensive
collage of muscle and other tests borrowed from physical therapy,
chiropractic and elsewhere. These tests are by no means universally accepted
or corroborated by science. They are often applied in static postures and
assessed by palpation, finger pressure or home-made combinations of string
and putty, but they seem to create an aura of thoroughness, scientific
precision and reproducibility that impresses clients into parting with tidy
sums of money. The fact that research has shown something like one third of
all such strategies to work because of a placebo effect ensures that there
will always be a significant number of satisfied clients to perpetuate some
healing myths.

At the opposite end of the scale, there are some therapists and even
individuals who never bother to rely on any therapists, who simply advocate a
rather generalised exercise, stretching and lifestyle regime in many cases of
musculoskeletal disorder. They apply few if any tests, advise clients to
work within sensible ranges of exercise intensity, modified by basic
perceptions of pain and effort – and lo and behold, they, too enjoy a very
significant degree of success!

This leads us to question if most functional tests, other than basic
palpatory assessments and those reported by the client in normal “functional’
activities, generally are a waste of time in the treatment of most
musculoskeletal disorders (excluding fractures, pathological disorders and
serious medical conditions). Are these static muscle tests for identifying
“weak”, “unfiring”, “imbalanced” and “lazy” transversus abdominis, rotator
cuff, multifidus, piriformis, psoas and other ‘key’ muscles generally
redundant or do they play an essential role in treating musculoskeletal
problems? Do exercises based upon such “muscle testing” methods definitely
enjoy a greater level of success than very general regimes based upon a
thorough classical medical ‘interrogation’ of the client?

Mel Siff
Denver, USA
Mel Siff Dot Com
Supertraining Twitter Feed

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
Mel Siff Dot Com
Supertraining Twitter Feed

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
Mel Siff Dot Com
Supertraining Twitter Feed

<< Someone posted before and I have tried with success a way to make your own
medicine balls. Take a kickball or soccer ball. Carefully pull out the
piece where the air goes in. It is just a rubber seal. Fill the ball with
sand or water and put the rubber seal back in. It really works! I filled a
small one with water and it doesn’t leak, it can bounce and it only costs a
few bucks! >>

Mel Siff:

***Yes, I posted that information a while ago. I have been making my own
medicine and “plyo” balls for many years from old basketball, water polo,
volleyball, soccer and other used balls and saved a fortune in the process.
When I used sand for making heavier medicine balls, I filled the balls with
very fine (river type) sand from the gold mines in South Africa (where I used
to live), so it was very easy to pour through an enlarged hole made in the
ball or even into the original bladder of the ball. In the USA, you can buy
some of the very fine construction sand to serve the same purpose. If I had
to make a larger hole instead of using the existing hole, I simply covered
the enlarged hole with a rubber patch.

To make balancing devices, I simply used a variety of used inner tubes from
cars, trucks and tractors inflated to a suitable pressure – again the cost is
little or nothing and one does not have stabilise the base, as one has to for
some physio ball routines. In using them as an unstable surface for standing
exercises, I simply place a large wood rectangular piece across the top of
the tube. Just another cash saving device for you! If you visit my gym in
Denver, you will come across many other such home-made training devices.

Mel Siff
Denver, USA
Mel Siff Dot Com
Supertraining Twitter Feed

Here is an extract from “Supertraining” that we discussed on some clinically
oriented groups a while ago. I felt it appropriate to repeat here, because
we often encounter spectacular claims about the magical power of some rather
dogmatic methods of ‘muscle testing’.

MUSCLE TESTING

Standard anatomical textbook approaches describing the action of certain
muscle groups in controlling isolated joint actions, such as flexion,
extension and rotation, frequently are used to identify which muscles should
be trained to enhance performance in sport. Virtually every bodybuilding
and sports training publication invokes this approach in describing how a
given exercise or machine ‘works’ a given muscle group, as do most of the
clinical texts on muscle testing and rehabilitation.

The appropriateness of this tradition, however, recently has been questioned
on the basis of biomechanical analysis of multi-articular joint actions
(Zajac & Gordon, 1989). This classical method of functional anatomy defines
a given muscle, for instance, as a flexor or extensor, on the basis of the
torque that it produces around a single joint, but the nature of the body as
a linked system of many joints means that muscles which do not span other
joints can still produce acceleration about those joints.

The anatomical approach implies that complex multi-articular movement is
simply the linear superimposition of the actions of the individual joints
which are involved in that movement. However, the mechanical systems of the
body are nonlinear and superposition does not apply, since there is no
simple relationship between velocity, angle and torque about a single joint
in a complex sporting movement. Besides the fact that a single muscle group
can simultaneously perform several different stabilising and moving actions
about one joint, there is also a fundamental difference between the dynamics
of single and multiple joint movements, namely that forces on one segment can
be caused by motion of other segments. In the case of uniarticular muscles
or even biarticular muscles (like the biceps or triceps), where only one of
the joints is constrained to move, the standard approach is acceptable, but not
if several joints are free to move concurrently.

Because joint acceleration and individual joint torque are linearly related,
Zajac and Gordon (1989) consider it more accurate to rephrase a statement
such as “muscle X flexes joint A” as “muscle X acts to accelerate joint A
into flexion”. Superficially, this may seem a matter of trivial semantics,
but the fact that muscles certainly do act to accelerate all joints has
profound implications for the analysis of movement. For instance, muscles
which cross the ankle joint can extend and flex the knee joint much more
than they do the ankle.

Biomechanical analysis reveals that multiarticular muscles may even
accelerate a spanned joint in a direction opposite to that of the joint to
which it is applying torque.

In the apparently simple action of standing, soleus, usually labelled as an
extensor of the ankle, accelerates the knee (which it does not span) into
extension twice as much as it acts to accelerate the ankle (which it spans)
into extension for positions near upright posture (Zajac & Gordon, 1989).
In work derived from “Lombard’s Paradox” (‘Antagonist muscles can act in the
same contraction mode as their agonists’), Andrews (1985, 1987) found that
the rectus femoris of the quadriceps and all the hamstrings act in three
different ways during cycling, emphasizing that biarticular muscles are
considered enigmatic.

This paradox originally became apparent when it was noticed that in actions
such as cycling and squatting, extension of the knee and the hip occurs
simultaneously, so that the quadriceps and hamstrings are both operating
concentrically at the same time. Theoretically, according to the concept of
concurrent muscle antagonism, the hamstrings should contract eccentrically
while the quadriceps are contracting concentrically, and vice versa, since
they are regarded as opposing muscles.

Others have shown that a muscle which is capable of carrying out several
different joint actions, does not necessarily do so in every movement
(Andrews, 1982, 1985). For instance, gluteus maximus, which can extend and
abduct the hip, will not necessarily accelerate the hip simultaneously into
extension and abduction, but its extensor torque may even accelerate the hip
into adduction (Mansour & Pereira, 1987).

Gastrocnemius, which is generally recognised as a flexor of the knee and an
extensor of the ankle, actually can carry out the following complex tasks:

(a) flex the knee and extend the ankle
(b) flex the knee and flex the ankle
(c) extend the knee and extend the ankle

During the standing press, which used to be part of Olympic Weightlifting,
the back bending action of the trunk is due not only to a Newton III
reaction to the overhead pressing action, but also due to acceleration
caused by the thrusting backwards of the triceps muscle which crosses the
shoulder joint, as well as the elbow joint. This same action of the triceps
also occurs during several gymnastic moves on the parallel, horizontal and
uneven bars.

This back extending action of the triceps is counteracted by the expected
trunk flexing action of rectus abdominis and the hip exension action of the
hip flexors, accompanied by acceleration of the trunk by the hip flexors.

Appreciation of this frequently ignored type of action by many
multiarticular muscles enables us to select and use resistance training
exercises far more effectively to meet an athlete’s specific sporting needs
and to offer superior rehabilitation of the injured athlete.

Finally, because of this multiplicity of actions associated with
multiarticular complex movement, Zajac and Gordon stress a point made by
Basmajian (1978), namely that it may be more useful to examine muscle action
in terms of synergism rather than agonism and antagonism. This is especially
important, since a generalised approach to understanding human movement on
the basis of breaking down all movement into a series of single joint
actions fails to take into account that muscle action is task dependent.

References:

Andrews J G (1982) On the relationship between resultant joint torques and
muscular activity Med Sci Sports Exerc 14: 361-367

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

Andrews J G (1987) The functional role of the hamstrings and quadriceps
during cycling: Lombard’s paradox revisited J Biomech 20: 565-575

Basmajian J (1978) Muscles Alive Williams & Wilkins Co, Baltimore

Mansour J M & Pereira J M (1987) Quantitative functional anatomy of the
lower limb with application to human gait J Biomech 20: 51-58

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

Mel Siff
Denver, USA
Mel Siff Dot Com
Supertraining Twitter Feed

You may recall a post on the value of belts in lifting which requested that I
review a series of articles which Paul Chek, a regular speaker on the fitness
circuit, recently wrote on the subject in Testosterone emag (see the archives
of the Supertraining eGroup). Relying on some rather dubious biomechanics
and clinical anecdotes, he deduced that all belt usage is detrimental to
lifting. Well, he posted some rather unhappy reactions to my review on
another weights user group. In one of these letters, he stated:

<<In summary, it is not a case of believing in the belly button “going in, or
going out”, it is a case of the order of events. If the body functions
correctly, segmental stabilization via the inner unit will prepare the system
for force generation. This is why I often say in my lectures, “in order for
the musculoskeletal system to stay healthy, stabilization must always precede
force generation”. >>

My response may be of interest to some of you:

*** “It is totally incorrect to state that stabilisation precedes
mobilisation. Neither is this taught or applied clinically in physical
therapy (e.g. in the application of PNF, Bobath etc), nor is it supported by
scientific research into the mechanisms of motor control. The annual
series of Bernstein memorial lectures on motor control offer just one source
of an extensive body of information which shows that stability is established
via ongoing feedback or error-correction processes acting on a foundation of
ongoing, varying levels of movement. If you have information to the
contrary, then you would be able to revolutionise the entire world of control
theory, not only in biology, but also in aeronautics, space exploration and
many other fields of human endeavour. And you would become an enormously
wealthy man in industry! ”

It is important to note that a system that is completely stable or following
a precisely described regular pattern (e.g. an unmodulated sine wave) carries
no information, so that it becomes very daunting to try to control a system
that tells you nothing about its current state. It is also fairly well known
that systems which are very close to equilibrium can display catastrophic
changes of state in response to very small perturbations (e.g. see work on
non-equilibrium systems by Nobel Prize winning scientist, Ilya Prigogine).

The process of stabilisation is by no means as simple and clearcut as Chek
seems to imply. Once again,this stresses how important it is for public
lecturers and authors in the fitness and training world to understand the
science behind the ideas and methods that they are trying to teach, sell or
apply.

Mel Siff
Denver, USA
Mel Siff Dot Com
Supertraining Twitter Feed

We often come across endless debates about the risk of using plyometrics, but
the case against the latter is usually poorly researched or emotively
argued, so let’s see if we can address a related issue in some more depth:

Is it possible to develop explosive speed and power without using plyometric
training? Can anyone quote past or present examples of world class
‘explosive’ athletes who have achieved their results without plyometrics or
combinations of plyometrics and free weights? In responding to these
queries, we also need to ask if it possible to entirely avoid the use of some
form of plyometric ACTION in sports training.

What does the example of gymnastics teach us, knowing that large numbers of
elite gymnasts do not use formal weight training or plyometrics?

How many elite Weightlifters use plyometric training (as opposed to fairly
conventional jumps)?

In answering these questions, let us draw upon logical science and practical
experience and avoid being drawn into the highly emotional territory which so
often characterises HIT and ‘Superslow’ discussions on this sort of topic.

Mel Siff
Denver, USA
Mel Siff Dot Com
Supertraining Twitter Feed

Siff MC “Supertraining” 2000 Ch 8

This well-known test may be applied in several different ways. Invariably it
requires the subject to leap from a standing position with a preliminary dip
and touch a measuring device sideways with one’s dominant hand. Recalling
the specificity of training, it is important to note that the results of this
test correlate best with conditions which are most similar to that of the
test. Therefore, it is useful to repeat the test with the non-dominant hand
or in the frontal plane with the athlete using both hands to reach for the
target. Moreover, there are several different initial conditions for
executing this test:

1. Starting statically from an optimum knee flexed position using no arm
swing
2. Starting statically from an optimum knee flexed position using arm swing
3. Starting statically from sitting on a low seat using (a) no arm swing, or
(b) arm swing
4. Starting dynamically with an optimal knee dip using no arm swing
5. Starting dynamically with an optimal knee dip using arm swing.

The major difference between the first two methods is that jumping without
armswing is intended to focus primarily on the role played by extension of
the lower extremity and trunk, without the picture being confounded by the
use of arm momentum. The major difference between the static and dynamic
starts is that the absence of an initial sharp dip allows one to focus more
on starting strength and the role played by the contractile (actin-myosin)
component of the muscle complex, instead of the more plyometric rebound
action encouraged by the use of the dip. This can sometimes assist one in
ascertaining whether the athlete needs more strength (or functional
hypertrophy) training or more rebound, nervous system training.

It can also be helpful to perform the static tests from different initial
knee angles to obtain a profile of individual jumping characteristics. For
example, if the maximum vertical jump is attained for a fairly large knee
angle, which is generally associated with a slower overall jumping time from
start to finish of the action, then it is obvious that the athlete needs to
concentrate on modifying his range and speed of maximal strength production.

Table 8.12 provides guidelines concerning the depth of loaded knee dips.
This reveals that the dip characteristically is deeper for heavier loads or
persons and that in all cases the pause during the dip should not last longer
than 0.25 second. Herein lies the benefit of performing push jerks or jerks
off racks with different weights as a form of supplementary plyometric
training. After all, plyometric training is of little value if it fails to
enhance adequately explosive strength or power over the range required in a
given activity. The use of drills which do not correlate strongly with the
functional needs of a given sport constitute one of the most common errors in
popular plyometric training…..

———————

Mel Siff
Denver, USA
Mel Siff Dot Com
Supertraining Twitter Feed

For example, cheating allows one to operate in a different way over one’s
strength curve and actually produces a different strength curve to achieve a
certain activity goal. The manufacturers of variable resistance machines
would have you believe that the use of cams, hydraulic systems and levers is
the only way to enable you to adjust to the varying leverages of a given
joint action. However, one can use cheating to take you past a weaker region
and enable you to load the stronger region, if you wish to overload
eccentrically or concentrically in a given region.

Contrary to what so many average personal trainers often believe, cheating is
not necessarily counterproductive or unsafe – it may actually produce
superior results, if one knows how and when to cheat over the full range of
joint action.

Cheating can permit one to produce a very different and more appropriate
’strength’ (torque, power or force) curve to enable one to overcome a load
more competently and safely. Very often, adherents of the slow training
philosophies militate against the power clean or derivates of it, and even
refer to such movements as ‘cheating’ movements which make allegedly
‘unsafe’ use of momentum and ballistic activity.

In fact, this type of ‘cleaning’ movement is a far more efficient way of
lifting a bar from the ground to the chest compared with the crude sort of
deadlift, reverse curl, upright row combination that so many folk use.
There are several other so-called ‘cheating’ movements which offer safer,
stronger and more efficient ways of overcoming a load.

A brief aside — If HIT or ‘Superslow’ methods are indeed ‘better’ than
Olympic and other ballistic methods, can one explain how SIB adherents raise
a heavy bar from the ground to the shoulders? Do they always unload the bar,
slowly raise it with a reverse curl to the shoulders, place it on a rack,
add more weights and only then perform the exercise?)

In other words, the term ‘cheating’ may well have to be redefined.
Bodybuilders know that the term really means using a movement which
deviates from the traditional or classical form in some way such as
swinging the weights or moving parts of the body to assist one in overcoming
’sticking points’. Unfortunately, many other folk believe that cheating is a
breaking of some training law, a serious crime against the body or the unfair
use of some method that is frowned upon by the purists.

In Powerlifting and Olympic Weightlifting, the rules of competition DO
legislate against certain types of ‘cheating’ or illegal lifting techniques,
such as uneven extension of the elbows, not completing the movement, allowing
the bar to stop during a lift, and using series of up-and-down bounces to
complete some lifts.

In the common world of resistance training, no such laws exist, only
guidelines – ’strict’ movements are defined as such, but they are not the
only way of doing any given lift. Variations very soon become the lifeblood
of the trainee who moves out of novice ranks, so cheating is a highly
acceptable technique in the training compendium of anyone who is serious
about progressing.

However, cheating does not necessarily produce better results by allowing one
to use his/her ’strength curve’ more effectively – it may simply be that
cheating allows one to use a heavier load over a certain part of the
movement, especially during the eccentric lowering phase, which is often
implicated in enhanced hypertrophy and strength production (though not so if
used for too long or too frequently). Ballistic forms of ‘cheating’ can
elicit a more powerful myotatic stretch reflex and produce greater muscle
tension with greater potential for enhancing strength and RFD (Rate of Force
Development).

It is really interesting to see how much more can lie in an apparently
simple and time-worn concept such as cheating – no wonder the world of
strength conditioning is so fascinating! There is always something new
lurking under the surface of everything that we often take for granted, even
after years of training and research. Thank goodness we now have the
Internet to allow ideas to be tested and disseminated far more rapidly than
ever before!

Mel Siff
Denver, USA
Mel Siff Dot Com
Supertraining Twitter Feed

<http://netra.exploratorium.edu/sport/faq11.html#anchor445332>

Q: How does Michael Jordan manage to hang in the air for so long when he goes
up for a slam dunk?

A: Actually, he doesn’t hang in the air any longer than any other basketball
player. It just looks that way. Once he leaves the ground, Jordan is governed
by the same laws of physics as the rest of us. How high he jumps depends
entirely on how much force he generates with his legs as he leaves the
ground. And how long he stays aloft is directly related to the height of the
jump: the higher the jump, the longer he stays in the air.

A vertical jump of four feet leads to a hang time of one second. That’s an
unusually high jump and, it turns out, most basketball players, including
Michael Jordan, don’t jump that high. A three-foot-high jump has a hang time
of 0.87 seconds. All the artistry of a slam dunk takes place in just eight-
or nine-tenths of a second!

Jordan makes it seem longer because he holds onto the ball longer than other
players before shooting or dunking, waiting until he’s on the way down to let
go of the ball. His tendency to pull his legs up as the jump progresses also
makes it seem like he’s staying higher than he really is.

Next time you watch the Bulls play, try to time how long Jordan stays aloft
and compare it to other players’ hang times. You’ll see there’s not much
difference.

—————

Q: Why do long jumpers “run” several steps in the air after they take off?

<http://netra.exploratorium.edu/sport/faq7.html#anchor452653>

A: The hitch-kick, as the running motion is called, stops the forward
rotation of the jumper’s body that he gets when he springs into the air. As
the jumper plants his foot for takeoff, the motion of his lower body stops
for the fraction of a second his foot is in contact with the board. But his
upper body continues to move forward, which makes him start to rotate forward
around his center of gravity. If unchecked, this rotation would send him
face-down into the sand.

Long jumpers have learned to counteract this rotation by moving their hands
and arms in the hitch-kick. During the hitch-kick, jumpers hold each leg
straight as it moves backward and bent at the knees as it comes forward. This
difference in leg position causes the jumper’s lower body to move forward.

Similarly, the jumper’s arm movements during the hitch-kick pushes the
jumper’s upper body backward. These body motions neutralize the takeoff
rotation and allow the jumper to get into a better position for landing

When the jumper stops hitch-kicking, the take-off rotation continues
unchecked. The jumper rotates forward around a line that goes from side to
side through his center of gravity. This rotation forces his legs (now
stretched out in front of him) downward.

—————–

Mel Siff
Denver, USA
Mel Siff Dot Com
Supertraining Twitter Feed