why Armstrong can't sprint

http://groups.google.com/group/wattage/browse_thread/thread/7ad454392f76b8f
Wattageの昔のアーカイブより。スプリントパワーとTTパワーは両立するのか?
いろいろ面白いネタが含まれていたので、かいつまんで。


■筋肥大⇒ミトコンドリア濃度低下、毛細血管密度低下⇒LT低下
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From: Andy Coggan
Date: Wed, 30 Jul 2003 08:46:00 -0700
Subject: RE: why Armstrong can't sprint

Amit Ghosh wrote:

> > My gut instinct is that one could probably do a better job of
> > maintaining neuromuscular power than I have (e.g., think CTS "Power
> > Stomps"), but ultimately there must be some trade-off (e.g., title of
> > this thread), stemming mostly from LT-type training diminishing
> > short-term power (and not the converse).
> Why would this be ? Do you have a mechanism in mind ?

Yes - with increased chronic use (e.g., endurance training, electrical
stimulation), the tendency is almost invariably for muscles to become
slower contracting, and hence less powerful. At the extreme this is
mediated via changes in the type of myosin heavy chain that is expressed
(i.e., true fiber type conversion), but even short of that point there
are changes in ancillary proteins (e.g., myosin light chains) that tend
to diminish the speed of contraction (but also conserve ATP). It is
therefore difficult for me to picture how you could develop LT to its
absolute maximum, which probably requires an extremely high training
volume, without there being at least some decline in maximal
neuromuscular power. (Although again, one can probably maintain it
better than I have...for example, via maintenance/alterations in
recruitment patterns.) OTOH, I can't as easily picture a mechanism by
which training focused on increasing neuromuscular power would diminish
threshold power...although I suppose extreme hypertrophy, resulting in
increased diffusion distances and mitochondrial "dilution", might be
one. Mostly, though, training to sprint well probably negatively affects
LT power simply via neglect.
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■完全なmuscle type(遅筋⇔速筋)の変換は起こりえる。
　limited degreeというけど、10%も増えたらすごいんじゃないのか。
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From: Andy Coggan
Date: Wed, 30 Jul 2003 09:27:00 -0700
Subject: RE: why Armstrong can't sprint

Rick Simpson wrote:

> I also remember that you cannot change fiber type with
> training except for a small class of fibers in the muscle.

There is no question that with extremes of activity (i.e., chronic
electrical stimulation for 8-24 h/d), complete fiber type conversion may
occur. IOW, the genetic "programs" exist and can be activated. The only
real question is the extent to which such fiber type transformation can
be induced through voluntary activity...most people working in the area
now acknowledge that it is possible, albeit probably only to a limited
to degree (e.g., somebody born 50/50 might, through many years of
strenuous training, raise the percentage of slow twitch fibers to
60-65%).
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