Sunday, 18 November 2012

[Supertraining] Digest Number 4633

1 New Message

Digest #4633

Message

Sat Nov 17, 2012 11:28 pm (PST) . Posted by:

"Jerry Telle"



> Jerry,
> Can you please produce the bibliography showing reverse muscle recruitment?
> A search on PubMed for Nardone (or Nardonne) and for reverse muscle
> recruitment didn't produce any pertinent result.
>
> Giovanni Ciriani - West Hartford, CT - USA
> P.S. your last two messages came directly to me and were not broadcast to
> the Supertraining community.
>
>

Giovannoi see ---JournalofPhysiology(1989),409,pp.451-471 451 With 8 text-figure.s
Printed in Great Britain

SELECTIVE RECRUITMENT OF HIGH-THRESHOLD HUMAN MOTOR UNITS DURING VOLUNTARY ISOTONIC LENGTHENING OF ACTIVE MUSCLES

BYA.NARDONE,C.ROMANOANDM.SCHIEPPATI*

From theIstitutodiFisiologiaUmana 1,UniversitadegliStudidiMilano, ViaMangiagalli32,I-20133Milano,Italy

(Received 8 March 1988)

SUMMARY

1. We have investigated the possibility that voluntary muscle lengthening contractions can be performed by selective recruitment of fast-twitch motor units, accompanied by derecruitment ofslow-twitch motor units.

2. The behaviour of motor units in soleus, gastrocnemius lateralis and gastro- cnemius medialis muscles was studied during (a) controlled isotonic plantar flexion against a constant load (shortening contraction, S), maintained plantar flexion, or dorsalflexionresistingtheloadandgraduallyyieldingtoit(lengtheningcontraction, L), (b) isometric increasing or decreasing plantar torque accomplished by graded contraction or relaxation of the triceps surae muscles, (c) isometric or isotonic ballistic contractions, and (d) periodic, quasi-sinusoidal isotonic contractions at different velocities. The above tasks were performed under visual control of foot position, without activation of antagonist muscles. The motor units discharging duringfootrotationweregroupedonthebasisofthephase(s)duringwhichtheywere active as S, S + L and L. The units were also characterized according to both the level of isometric ramp plantar torque at which they were first recruited and the amplitude of their action potential.

3. 5unitswereneveractiveduringdorsalflexion;someofthemwereactiveduring the sustained contraction between plantar and dorsal flexion. Most S + L units were active also during the maintenance phase and were slowly derecruited during lengthening; their behaviour during foot rotations was similar to that during isometric contractions or relaxations. L units were never active during either plantar or maintained flexion, but discharged during lengthening contraction in a given range of rotation velocities; the velocity of lengthening consistently influenced the firing frequency of these units. Such dependence on velocity was not observed in S+L units.

4. A correlationwasfoundbetweentheamplitudeoftheactionpotentialandthe threshold torque ofrecruitment among althe units. In addition, the amplitudes of both the action potential and the threshold torque were higher in the case of L units than in the case of S and S + L units. Most L units could be voluntarily recruited only in the case of ballistic isometric or isotonic contraction.

* To whom alcorrespondence should be addressed.

15-2

452 A.NVARDON.E, C.ROMA.N4OAND M.SCHIEIPAT-TI

5. Occasionally, L units were directly activated by electrical stimulation of motor fibres and their conduction velocity was in the higher range for ax-axons. In contrast, nerve stimulation could induce a reflex activation of S and S + L units.

6. The results suggest that a large proportion of high-threshold, fast-twitch motor units, most likely characterized by a short half-relaxation time. are active (luring lengthening contractions. The mechanical advantage of their selective recruitment and the possible neural mechanisms responsible for it are briefly considered.

Begin forwarded message:

> From: Giovanni Ciriani <Giovanni.Ciriani@Gmail.com>
> Subject: Re: [Supertraining] Slow twitch hypertrophy.--Brock
> Date: November 12, 2012 7:19:01 AM MST
> To: Supertraining@yahoogroups.com
> Reply-To: Supertraining@yahoogroups.com
>
> Jerry,
> Can you please produce the bibliography showing reverse muscle recruitment?
> A search on PubMed for Nardone (or Nardonne) and for reverse muscle
> recruitment didn't produce any pertinent result.
>
> Giovanni Ciriani - West Hartford, CT - USA
> P.S. your last two messages came directly to me and were not broadcast to
> the Supertraining community.
>
> On Sun, Nov 11, 2012 at 10:47 PM, <jrtelle@aol.com> wrote:
>
> > oooppps my sincerest i got a new Mac and messages are everywhere in a
> > strange fornat! I'm on my old one now so no excuses. I was so frustrated I
> > waited to finish my message on this one.
> >
> > In particular Mr Giovanni Ciriani writes " From an intuitive point of
> > progressive,
> >
> > view, because muscle (and force) recruitment is always
> >
> > NOT SO -- A FELLOW NAMED NARDONNE APPARENTLY REVERSED ORDERS IN
> > ECCENTRIC ACTIONS AND SOME ONE ELSE? MIGHT HAVE DONE SO WITH EXPLOSIVE HIGH
> > LOAD CONCENTRICS? I would
> >
> > expect that one always engages slow twitch fibers, but not always fast
> > twitch fibers.THIS MAY NOT BE TRUE WITH SOME FIBER TYPES INDICATING AN
> > INCREASE IN IIB FIBERS SIZE ?? AND NUMBER??As a consequence, it's not
> > possible to engage fast twitch
> > fibers without first engaging slow twitch ones. DON'T BET THE FARM YET! I
> > HAVE REAMS OF STUDIES TO LOOK THROUGH
> >
> >
> > Jerry Telle
> > Lakewood CO USA
> >
>
> >

[Non-text portions of this message have been removed]

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