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Dear Glenn Your settings may not be correct in the JISCMAIL websie if you are not receiving copies of your own mailings. Have a look at www.jiscmail.ac.uk Robert ----- Original Message ----- From: "glenn alan welke" <[log in to unmask]> To: <[log in to unmask]> Sent: Friday, January 12, 2001 02:24 Subject: Re: Correct Muscle Action? (fwd) > Hello, > I sent this message out to the list a few days ago but am not real sure it > went anywhere as I did not get a copy in my box. Sorry to bother with a > double post if that is what this is. > Glenn > > ---------- Forwarded message ---------- > Date: Wed, 10 Jan 2001 08:27:33 -0500 (EST) > From: glenn alan welke <[log in to unmask]> > To: PHYSIO - for physiotherapists in education and practice > <[log in to unmask]> > Subject: Re: Correct Muscle Action? > > Hello, > I am a physical therapist with not much training in formal biomechanics > or EMG stuff. In reading this post aabout correct muscle action it seems > that it indicates that there is an improvement in the "core stability" of > the lifters within their training session. Does not the decrease in > external sway... indicate an increase in the central postural control/ > proprioceptive response system? Would'nt the variation in the EMG > activity of the trained lifters indicate the rapidly changing muscle > activity that would be required to maintain a more precise trajectory? If > my thinking is along the correct lines I do not see why this is the > opposite of what would be expected if the "correct muscle recruitment" > hypothesis were to be believed. Does this mean that if the correct muscle > recruitment hypothesis was correct that there would be less EMG activity > as well as less sway/smoother trajectory of the lift? My understanding of > core stability is that it is a pattern of muscle recruitment that improves > stability centrally that allows a more precise movement distally. It is > not meant to produce a rigidity which would seem to make precision more > difficult. Trunk stability is a concept that therapist that work with the > neurologically involved population have used for years on an intuitive > basis I guess. > Thanks for reading this jumbled message, > Glenn > > > On Fri, 5 Jan 2001 [log in to unmask] wrote: > > > Currently there is a great deal of discussion of the "correct" posture and > > pattern of moving or lifting, but there are at least two processes involved: > > > > 1. The 'correctness', precision, repeatability of the external movement of > > the body > > 2. The 'correctness', precision, repeatability of the internal muscle > > involvement > > > > Most of the discussion of core stabilisation, transversus abdominis > > recruitment and rotator cuff action suggests that both of the above processes > > take place in a very deterministic manner. Thus, it is implied that the > > pattern of external posture or movement is "correct" if the pattern of > > internal muscle involvement is "correct". Moreover, this also implies that > > the same pattern of muscle action always produces the same output motor > > pattern and any other pattern of muscle action cannot do so. > > > > This functional relationship, however, has not been confirmed to be correct, > > yet it is assumed so often that many folk seem to accept that it is virtually > > a law. Several studies involving simultaneous video recording of the > > external movement and EMGs of given muscles has shown that this assumption is > > far form the truth. > > > > For example, the Russian scientist Pakhamov analysed the variation in muscle > > EMGs during the Olympic lifts and found that the least variation took place > > in the external movement, but there was significant variation in the EMG > > indicators (Zhekov IP "'Biomechanics of the Weightlifting Exercises', 1976). > > Interestingly, the variation of all the functional indicators decreases with > > increase in load on the bar, but was much wider with light loads or no loads > > at all. > > > > During a prolonged training session, the degree of variation changed. With > > novices and lower qualified lifters, the variation decreased during the > > middle of the session, but rose towards the end. In highly qualified > > lifters, it was very interesting to discover that, as the variation in the > > trajectory of the bar decreased, the variation in EMG increased, which is > > precisely the opposite of what would be expected if the ideas of the "correct > > muscle recruitment" hypothesis are to be believed. > > > > As Zhekov noted, this corroborates Bernstein's hypothesis that, in the > > repeated reproduction of a movement, one observes a "repetition without > > repetition". Apparently, the variation is a general characteristic of > > programmed movement which allows one to create and store different motor > > programs and to select the optimal movement variant in a given situation. > > This variational principle, according to Pakhomov, provides a large > > reliability to enable the athlete to produce the required movement. > > Furthermore, this switching between controlling and muscle groups serves to > > delay the onset of fatigue and minimises any increase in injury risk. > > > > Dr Mel C Siff > > Denver, USA > > [log in to unmask] > > >