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nmaffiuletti78
05-19-2008, 09:49 PM
Dear List members,

to investigate the characteristics of the compound muscle action potential
(M wave) and of the isometric twitch of human muscles in vivo, "supramaximal"
electrical or magnetic nerve stimulation is used.



I have some problems with the definition of "supramaximal", since the
criteria for "supramaximality" reported in the literature appear somewhat
arbitrary, e.g., intensity of the maximal response (either M wave or peak
twitch) +10%, +20%, +50%, +100%, + a given voltage (25-30 V), fixed voltage
(135-160 V), fixed amperage (100 mA), percentage of stimulator power output,
etc. (I have checked almost all the papers in which this methodology has
been used). Some authors failed to describe their "supramaximality"
criterion, and others used "maximal" rather than "supramaximal" stimuli,
i.e., intensity of the maximal response (either M wave or peak twitch).



I am also quite confused about the definition of "plateau" for the maximal
response (either M wave or peak twitch) with increasing stimulation
intensity. A "true plateau" in M wave and/or peak twitch amplitudes with
increasing stimulus intensities is rarely observed. Rather, a "near plateau"
with small increments/decrements (depending on the highest intensity
attained) in M wave and/or peak twitch with increasing stimulation intensity
are obtained.



Are you aware of any studies reporting evidence-based indications regarding:

- the use of maximal vs. supramaximal stimulus intensity?

- the best criteria for supramaximality (M wave or peak twitch and at what
intensity)?

- the best criteria for the definition of a (near) plateau?



Thank you I'll post a summary.

Ciao !

Nik



Nicola A. Maffiuletti, PhD

Head, Neuromuscular Research Laboratory

Schulthess Clinic

Lengghalde 2 - 8008 Zurich

Switzerland

Phone +41 44 385 75 79

Telefax +41 44 385 75 90

Nicola.Maffiuletti@kws.ch