Here is a discussion from the Supertraining discussion group which may also
be of interest here.
It was written:
<Then there is the idea of the right side vs. left side imbalances. I once
listened to a presenter (John Blievernicht, I think - is he still around
promoting his 'balancing acts'?) at an NSCA conference talk about this. He
demonstrated a nifty little squat test on a balance board and said a Right to
Left side leg muscle imbalance was present if the athlete could not balance
the board while doing a body weight squat on it. I'd imagine that you could
easily cheat that test, even if one leg was way stronger!! >
*** This balance board test is meaningless. Together with some postgrad
physio students of mine, I carried out tests with instrumented balance boards
(of different diameters and damping ratios) resting on force plates and touch
sensitive contacts and we found no such simple correlations. What we did
find is that the ability of the individual to rapidly establish balance after
perturbation (at varieties of foot spacings and configurations) was far more
important for sporting prowess and injury prevention than the simple ability
to balance on a wobble board or physio ball. Balancing, of course, is far
more difficult with a narrow foot spacing, but we found that competent
gymnasts were excellent at rapidly balancing themselves, even with narrow
foot spacing.
The ability of the non-injured athlete to balance with a squat has little or
nothing to do with relative left-right leg strength; this has far more to do
with nervous control of the muscles, which that conference speaker would have
appreciated had he consulted some of the literature on motor control or if he
had carried out any biomechanical research into the issue of balance.
<In reality, it is probably quite normal to have a stronger leg anyway. I
recall Lynn Jones from the US Olympic Training Center summarizing some
research that was done on elite weightlifters in Colorado Springs using dual
force plates - one for each foot. Almost none of the lifters produced
symmetrical force profiles on both legs. At first they thought this was a
problem and tried to fix it, to no avail. Since these apparent "imbalances"
did not seem to be causing any decrease in performance, I think they decided
to leave it alone and chalk it up as "the norm". What do you all think?
*** Yes, this apparent 'imbalance' is quite normal and is characteristic of
attempts by the body to stay within a certain region of homeostasis. Since
perfect balance or homeostasis is not attainable in a dynamic system like the
body in motion, the body "hunts around" using feedback from the
proprioceptors, vestibular system and other sensory systems to keep it in a
type of dynamic balance within a certain range of tolerances.
This sort of research has been carried out frequently on lifters and it is
virtually unheard of to observe symmetric patterns of Left-Right force
production in any lifters (or any other athletes). As I have remarked in
earlier letters, it is common for different patterns of muscle action to
produce the same skilled external movement, so that these simplistic beliefs
about muscle balance and symmetry have nothing to do with reality. I have
also recorded similar results with powerlifters.
Moreover, the patterns of force production do not consistently favour left or
right throughout any movement, but can change from side to side as the lifter
or athlete makes ongoing adjustments. If this type of continuous adjustment
did not occur, it would mean that once a movement is a little too much to one
side, then it would always remain so, thereby usually culminating in an
unsuccessful or dangerous lift.
All space probes aimed at certain very distant planetary targets function in
this same feedback guided manner and that is how such orbiting or landing
precision is attained. So, when you next see how the Space Shuttle docks
with Mir or the latest orbiting station, just appreciate that the process of
achieving such accurate docking relies on processes much like those
left-right-up-down manoeuvres used by competent lifters and other athletes.
No scientist ever expects space vehicles to reach their targets with perfect
symmetry of control - our bodies are no different, because nature is an
outstanding educator. The overall scheme is known as "cybernetics" - the
science of control and communication, or the way in which control is
facilitated by communication between the input (or sensory) and output
(motor) systems of any technological or living system.
We can apply this same science to those very overplayed and unnecessary
schemes used for recruiting abs, transversus, psoas and many other isolated
muscles in the healthy person - or for stabilising the core or balancing
agonists and antagonists - but enough has already been expressed on that
topic for a while!
Dr Mel C Siff
Denver, USA
http://groups.yahoo.com/group/Supertraining/
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