Dear Mel

As brilliant and as thought provoking as ever. If you noticed in my response
I was very careful to avoid this issue, ie introduce the anatomical position
of muscles and not their physiology. I have done may MB courses and never
heard a tutor yet say this muscle is purely tonic and this is fast twist.

I agree muscles fibres can change their specificity, one needs only to look
at the changes in muscle composition after spinal cord injury.

With regard to the sit up thing, I wonder how truly isolated a sit up is to
the abdominals ? When ever I have done lots, some considerable time ago now,
I recall it was often my thighs that tired first so the record book account
would only hold water if we could observe the attempt in progress. Like any
activity smal changes can switch the muscular emphasis to other groups.

Finally as muscles are complex systems of many different fibres an agrument
might exist for the targeting of certain types of work, ie low grade effort,
postural training. If this effort exceeds the threshold for this fibre type,
then the fast twitch may come to the fore.

Be gentle Mel and remember these are theories I have heard and not my own.
Warm Regards Kevin Reese PT UK
-----Original Message-----
From: [log in to unmask] <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: 16 October 1999 02:16
Subject: PP125: MUSCLE PARADOX


>Here is a quick return to a little forum that I offered periodically up
until
>a few months ago.
>
>PUZZLE & PARADOX 125
>
>INTRODUCTORY NOTE
>
>For newcomers to this forum, these P&Ps are Propositions, not facts or
>dogmatic proclamations. They are intended to stimulate interaction among
>users working in different fields, to re-examine traditional concepts,
foster
>distance education, question our beliefs and suggest new lines of research
or
>approaches to training.  We look forward to responses from anyone who has
>views or relevant information  on the topics.
>
>PP 125   MUSCLE FIBRE PARADOX
>
>"Attempts to apply research on muscle fibre types may be misleading and
>premature."
>
>Frequently we encounter advice about the appropriate way of training or
>rehabilitating certain muscle groups in terms of their relative proportions
>of the different types of muscle fibre.
>
>Since "fast twitch" fibres apparently play the dominant role in the
>production of strength type activities and "slow twitch" fibres dominate in
>lower intensity, more endurance type activities.  Bodybuilding articles
often
>refer to the need to increase muscle hypertrophy by addressing the
>contributions of the different types of fast twitch or fast fatiguing
fibres.
>
>Something that apparently seems to contradict such views and
recommendations
>concerns that mystical region that everyone wants to exercise and shape,
the
>abdominal muscles.  The Guinness Book of Records shows that the world
record
>for continuous sit-ups is in the region of 20 000, a daunting effort which
>took several hours longer than the average running marathon.
>
>Various authorities are quick to point out that the abdominal muscles are
>predominantly fast twitch in nature (estimates of FT fibres run as high as
>75%), which should imply that these muscles would not be ideally suited to
>such excessively prolonged endurance work.
>
>How is it possible for so-called fast twitch muscles with impoverished
blood
>supply and energetic capabilities to sustain such long periods of strenuous
>activity?   Does the much smaller content of slow twitch muscle enable such
>tasks to be handled very effectively?
>
>Does this mean that ratios of different fibres are relatively unimportant,
>and that, as long as there is a significant proportion of each different
type
>of fibre, then that muscle group will be able to manage both "slow"
>(endurance) and "fast" (high intensity) tasks quite competently.  Does this
>suggest that an overemphasis is being placed on determination of exact
>proportions of fibre types for enhancing the quality of training programs?
>
>Does this imply that almost any type of muscle fibre can be conditioned to
do
>almost any task or does it mean that many of our recommendations about the
>relevance of fibre type to different types of physical performance needs
some
>serious revision or qualification?
>
>Comment on the above questions, by drawing upon relevant references or your
>own theories and experience.
>
>Dr Mel C Siff
>Denver, USA
>[log in to unmask]
>



%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%