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James Dowling
10-08-1998, 03:22 AM
Without entering the weights vs machines debate, I think it is important
to clear up a fallacy that may be widely accepted in the athletic training
community regarding the measurement of the utilization of stored elastic
energy in human movement.

On Wed, 7 Oct 1998
JRTELLE@aol.com wrote:

> *** What about the Squatting Jump test (Concentric only activity) and the
> Counter Movement Jump test (Concentric activity preceded by pre-stretch
> of muscles). These tests have been extensively used by us and by every
> scientist to measure the possible re-use of elastic energy and the neural
> activities here connected.

Since the publication of this method by Komi and Bosco (1978), it has been
mathematically proven that muscle can produce more work in the concentric
phase of a stretch-shorten cycle in the absence of any elastic elements to
store energy and without any increase in the neural drive due to the
stretch reflex (Dowling, Human Movement Science 11:273-297, 1992). The
late great Gerrit Jan Van Ingen Schenau referred to the increased height
of a counter-movement jump over a squat jump as simply a "rise time"
phenomenon in which the only purpose of the counter-movement is to allow
time for the muscle to become fully activated before the start of the
concentric phase. Since muscle requires time to increase force, the squat
jump spends less of the range of motion at maximum activation than the
counter-movement jump and therefore produces less force and does less work
over the same distance. I personally believe that some of the extra work
is due to stored elastic energy release but it is quite clear that one
cannot simply attribute all of the work differences to this phenomenon.
The calculation of utilization of stored elastic energy is still a problem
for muscle researchers. Some advances have been made on animal muscle
(i.e. Roberts, et al. Science 275:1113-1115, 1997 and Ettema, J Exp Biol
199:1983-1997, 1996) but I know of no similar methods that could be used
with athletes at this time.

Jim Dowling, Ph.D.

Associate Professor of Biomechanics
Department of Kinesiology
McMaster University
1280 Main Street West
Hamilton Ontario L8S 4K1
CANADA
(905) 525-9140 ext. 23572
Fax: (905) 523-6011

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