On 10/2/99, Heather<[log in to unmask]> wrote:

<<When I was giving the aerobics classes, there were facilities which were 
expanding that were looking into the different designs of shock absorption. I 
also taught at the YMCA, which DIDN'T  use a shock-absorbing floor, and the 
difference was just incredible. SOOO damaging  and restriciting! I am sure 
that high impact activity would cause injury. >>

***It is not only the floor that is important in minimising injuries, but the 
manner of landing, in particular.  In fact, a sprung wooden floor which has 
an inappropriate resonant frequency or which is sprung or suspended in 
inappropriate places, can increase the incidence of injury.    This is 
because the floor may load the limbs even more strongly when it rebounds and 
strikes the soles of the feet.  For reasons such as this, it can be very 
costly to have a properly suspended and tuned wooden floor installed.

Interestingly, I used to teach several aerobics classes, including high 
impact, for more than 12 years and I operated on the linoleum-covered 
concrete floor while my classes exercised on the absorbent flooring in the 
centre of the gym.  Despite my weighing close on 100kg (220lbs), as a 
competitive Olympic weightlifter, I never once experienced 'shin splints' or 
any lower extremity trauma.  

However, I strongly took to heart what Barishnikov and other top ballet 
dancers stressed, namely floating and elevation.  Muhammed Ali in the context 
of nimble boxing, said "Float like a butterfly, sting like a bee".  In other 
words, the acquisition and continued demonstration of efficient motor skills 
(plus the reactive ability to correct rapidly for any serious imprecision) 
under a wide range of conditionsis vital for prevention of injury.

Curiously, I sometimes tend to find the explosive kicking in free space in 
karate stresses my knees far more than aerobics and controlled Olympic 
lifting, plus I have noted among some elite karateka with whom I have trained 
for many years have a high proportion of hip problems.  Has anyone come 
across research into injuries resulting from unresisted kicking into free 
space, akin to the shoulder injuries associated with throwing and pitching 
light balls?

Stationary cycles and 'Spinning' type activity also stress my knees more than 
fully squatting and Olympic jerking, so I generally avoid this type of knee 
workout that does not facilitate the crucial follow through phase of other 
sporting movements.  This I can understand more readily, because of research 
done in the UK that indicates that prolonged cyclical activity is more 
damaging to the joints than periodic impulse loading, and was associated with 
a higher level of osteorthritis (I am pretty sure that I posted references on 
this topic more than a year ago, so they should be archived somewhere).
  
In addition, I believe that, if we persist through the uncomfortable phases 
of exercising, we eventually adapt to the sub-acute pain or other feedback 
associated with many sporting activities, and can train for years with our 
altered perception of pain and begin to suffer breakdown only years later.  
Very often, we may have stopped doing those initial damaging sports, and 
taken up something completely different, so that a causal analysis often 
becomes very difficult and attempts at understanding aetiology may be 
seriously flawed.

Dr Mel C Siff
Denver, USA
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