What does HIT stand for?
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Sendt: 26. oktober 2001 08:00
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Emne: Impact Loading and Bone Strength
The innovative study below showed that impact loading not only increases
bone
density in the parts of the skeleton that are directly involved with the
loading, bit also increases bone density in certain parts of the body where
bone mass might decrease. In the case of the gymnasts who were studied,
this
might suggest that girl gymnasts who lose body and bone mass may well
compensate by increasing the density and strength of the less bulky bones.
No
doubt, this effect would be profoundly attenuated if the loss of bone mass
were due to osteoporosis associated with dieting or anorexia.
Now, to take this further, has any research been conducted on strength type
athletes who indulge in impact and non-impact training? The above results
initially suggest that non-impact training such as HIT, 'superslow' and
machine-exclusive strength training may be associated with producing a body
with a higher percentage of bone mass (and possibly weaker bones) than their
colleagues who use impulsive and ballistic types of training regularly (like
gymnasts). The latter might have lighter, stronger bones and muscles
(relative to their bodymass) than their non-impulsive colleagues, something
that seriously needs to be examined in the case of strength athletes like
American footballers. A most interesting speculation indeed!
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Skull bone mass deficit in prepubertal highly-trained gymnast girls.
Courteix D, Lespessailles E, Obert P, Benhamou CL. Int J Sports Med 1999
Jul; 20(5): 328-33
It is known that impact loading sport can increase the bone mineral density
in the stressed sites of the skeleton in athletes. However, non
weight-bearing sites are seldom studied in healthy young girl athletes.
In order to study the effects of a long term intensive training on the
non-stressed region of the skeleton (skull), we investigated both
highly-trained girl athletes, involved in sports requiring or not
significant
impact loading on the skeleton and a girl control group. Bone mineral
content
(BMC) and density (BMD) were measured in the whole body, at lumbar spine,
femoral neck, trochanter, Ward's triangle, radius, head and ribs, in 60
prepubertal girls including 12 swimmers, 32 gymnasts and 16 controls.
Measurements were made by DXA.
There were no statistical differences between the groups as regards age,
height, body weight, body mass index, lean tissue mass and dietary calcium
intake. Mean BMD in gymnasts was statistically higher than in other groups
for radius, femoral neck and Ward's triangle while there was no difference
between swimmers and controls.
Head BMC was significantly lower in gymnasts compared to other groups (241.9
± 41 g vs. 285.8 ± 34.7 g and 291.1 ± 50.2 g respectively in swimmers and
controls. The same observation was made for head BMD. When body weight was
used as a covariant, the contribution of the head BMC to the whole body was
significantly lower in gymnasts (24.97%) than in swimmers (27.88%) and
controls (27.77%). When compared between groups, the slopes of the
regressions for head/whole body BMC or BMD were significantly lower in
gymnasts than in other groups.
These data suggest that in prepubertal children the increased bone density
induced by gymnastic training in the stressed sites of the body could be
related to a decreased skull bone mass.
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For anyone who may be interested in reading more about this sort of work, I
have summarised and reviewed several other research articles that have
analysed the effects of exercise on the skeletal system on the Supertraining
site at:
http://groups.yahoo.com/group/Supertraining/
Dr Mel C Siff
Denver, USA
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