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jcbio-force97
02-07-2007, 01:43 AM
André Rodacki wrote:

We performed an experiment that involved abdominal exercises (3 sets of
three 3 series of 20s with interval of 30s) and measured spinal length
immediately after. We measured spinal shrinkage using a precision
stadiometer (Rodacki et al., 2001, Boocock, 1996) that allows assessment
of small stature changes.

Interestingly we found stature increases, which indicate an acute spinal
unloading.

Abdominal exercises are thought to produce compressive forces (McGill,
1998, Phys Ther 78 (7) p. 754-765) that reach high values (varying from ~
1700 to 3500 N). Thus, we are struggling to explain our stature growth
after exercising, which were very consistent between subjects. These gains
at the end of the exercises were greater than that observed during the
same period of time (4.5 min) in a resting posture (Fowler position),
which is a well known unloading posture used to relief LBP.

How can the intervertebral discs to increase height under compressive
forces? This is opposite to what we have found in the literature and seems
to be at least puzzling.

Any comments on possible underlying mechanisms will be welcome.

John Casler writes:

Hi Andre,

I think you may be viewing the crunch action as a "compressive" action, when
in fact it is a "cyclic compression and decompression to the anterior disc,
as well as a cyclic decompression and only slight compression to the
posterior disc".

This cyclic compression and decompression, may have a tendency to actually
draw in or pump up the disc body.

In the lying position axial loads are reduced and the discs are mildly
decompressed by comparison. As you begin each crunch the anterior disc is
compressed, while the posterior is decompressed slightly. As the trunk
returns to flat the anterior decompresses and depending on form, the
posterior might slightly compress, but to be sure it still cyclically has a
change in pressure.

I have developed a "loaded" action, performed in the standing position that
has a progressive load/force that reduces the amount of Lumbar Flexion,
(which is not always a good thing) yet still provides a quite stable load to
the abdominal and torso musculature that I feel can produce a better effect,
and possibly even produce enough action to assist in healing or repair (if
that is possible).

Additionally the load/force is a decompressive load axially (tractive).

Regards,

John Casler
TRI-VECTOR 3-D Force Systems
Century City, CA