On 4/2/00, Liz Williams<[log in to unmask]> wrote:
<< Trevor Allen is a researcher at the School of Physiotherapy, The
University of Melbourne, who lectures our post-graduate physiotherapy
students in muscle physiology - forwarded by Liz Williams, Lecturer >>
Mel Siff:
***I would happily like to respond fully to this letter, but it came over as
such a daunting collage of clips and pastes from several different people and
myself that I really couldn't make much organised sense out of it. It will
take me time to reformat and rearrange that material, unless it can be sent
over in a more readable form. Anyway, I have examined what came through most
clearly in that mail. I had to identify the author in an uncertain way
because of all the different types of paretheses and arrows.
Anyway, without entering into an extremely long analysis of every comment, I
cannot see any scientific errors of note in my comments on the dubious
physiology underlying Pilates training or the inaccurate or imprecise remarks
made by Trevor Allen that seemed to be trying to support Pilates
pseudo-science.
Interestingly, the added remarks of Liz Williams, if read carefully alongside
my earlier letters, actually lend support to my critique of some of Trevor
Allen's points and I must thank her for furnishing them. Unfortunately, both
Trevor Allen and Liz Williams both admit to not knowing much about Pilates,
so that they have been unable to assist us in moving much further on the
Pilates issue.
However, there a few of the more important points that I will address.
Liz Williams? asked:
<<How does this explain Hill's Force-Velocity curve which we see in every
muscle physiology text? According to that, the highest tensions occur during
high velocity eccentric contractions. >>
Mel Siff:
***The Hill curve was not derived under ballistic or explosive conditions and
several studies have been undertaken showing that it should not be
extrapolated to mean that an hyperbolic F-V relationship applies in all
situations. See, for example:
Bosco C (1982) Physiological considerations of strength and explosive power
and jumping drills "Proc of Conference '82: Planning for Elite Performance",
Canadian T&F Assoc Ottawa, 1-5 Aug 1982: 27-37. Here, Bosco shows a fairly
linear increase in Force with knee angular velocity during jumping and
running.
Liz Williams? stated:
<<Ballistic or high velocity stretches will not induce a greater lengthening
of the muscle-tendon unit (as a whole) than slow stretches if they occur over
the same anatomical range.>>
Mel Siff
***The magnitude of stretching is dependent on the magnitude of the imposed
load, whether the soft tissue involved is regarded as elastic or
viscoelastic. If one imposes a large impulse ( F* delta T) that imposes more
tension in the tissue than a slow stretch (that does not last for many
minutes), it will stretch it further - basic physics. Large force = large
deformation. Research also shows that the compliance of the tissues is rate
dependent and that if you impose a load for a prolonged period, then you can
actually deform the tissues, but that is not the scenario involved in Pilates
exercise. That remark about "same anatomical range" implies that you are
limiting the movement to a fixed range and therefore puts an upper
architectural upper limit to stretching, something that we all are familiar
with.
Someone (Liz Williams?) wrote:
>When muscles are connected to the skeletal system we have to talk about
>angle-torque relation of muscles since the muscles are attached across
>bones (usually via tendons), and muscle length ranges are limited by the
>range of motion of the joint(s). In this case muscle length is altered by
>movement of a limb(s) about a joint(s), which will also alter moment-arm at
>the same time. For some muscles the angle-torque relation is similarly
>shaped to the length-tension relation (i.e. there is still both an ascending
>and descending limb), and although not always the case, many muscles are
>stretched onto their descending limb within the anatomical range of the
joint.
Mel Siff:
***This simplistic modelling of joint action has to be applied with careful
circumspection, because modern biomechanics research reveals that muscle
action in a remote joint can produce movements and accelerations about joints
that are not even spanned by that muscle. See for instance:
Zajac F & Gordon M (1989) Determining muscle's force and action in
multi-articular movement Exerc Sport Sci Revs 17: 187-230
Mel Siff:
>>Resting muscle length is determined in any individual by the distance
between the sites for its two bony attachments (often called its origin and
insertion), i.e., genetically inherited joint architecture, and has nothing
to do with Pilates exercises.
To which someone (Liz Williams?) responded
<<What about tendon length and compliance? What about muscle fibre pennation
angles? What about resting muscle activity? What about length, architecture
and activity of other muscles working across the same
joint(s)? (agonist and antagonist).>>
Mel Siff:
*** It looks as if a point is deliberately being hunted for. The length of
any soft tissue connected between two fixed point is not a function of
anything but the geometric distance between the two points. Mechanical
properties will affect the performance of the system once loading is imposed
by inertia or neural excitation.
Mel Siff:
>>If muscles is stimulated by nervous excitation, it can NEVER lengthen
relative to its unactivated state.
Someone (Liz Williams?) responded:
<<Wrong. An external force such as gravity can forcibly stretch a muscle to
beyond its resting length while contracting, as long as anatomical limits
allow it to do so. >>
***More wrong. Invalid comparison - my comment referred to muscle that is
stimulated actively, not subjected to passive inertial stretching. We all
know that a resting muscle can be stretched passively beyond its rest length,
but it is a very different matter in an active muscle.
Dr Mel C Siff
Denver, USA
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