Document 0510
 DOCN  M9610510
 TI    M-wave modulation at relative levels of maximal voluntary contraction.
 DT    9601
 AU    Nagata A; Christianson JC; Waseda University, School of Human Sciences,
       Saitama-ken, Japan.
 SO    Eur J Appl Physiol. 1995;71(1):77-86. Unique Identifier : AIDSLINE
       MED/96040681
 AB    Frequency (mean and median power frequency, f and fm) and amplitude
       (average rectified and root mean square values, ARV and rms), parameters
       of the M-wave, and the dorsiflexor force parameters of the anterior
       tibial muscles were measured in seven healthy human subjects.
       Intermittent, voluntary contractions at relative intensities (40%, 60%,
       and 80%) of maximal voluntary contraction (MVC) were performed in
       conjunction with electrical stimulation. The M-wave parameter changes
       were measured over the course of the isometric contractions. At higher
       force levels, M-wave potentiation was observed as increases in both ARV
       and rms. The ARV augmentation attained levels as high as 206.1 (SD 7.4)%
       of resting values after both initial and final contractions of 80% MVC,
       reaching statistical significance (P < 0.01). The f and fm failed to
       show a significant difference at any level of contraction. It was
       surmised that potentiation of the M-wave was the result of an increased
       contribution of muscle fibre type IIb recruited during higher
       contraction levels, reflecting the change to larger, deeper innervating
       motoneurons as the intensity of contraction, as a percentage of MVC,
       rose. Recruitment of type IIb fibres, which have been reported to have a
       higher energy potential and frequency content, were thought to reflect
       changes in the local excitability threshold of some motor units as the
       force intensity increased during the intermittent voluntary
       contractions. It is suggested that the M-wave elicited after
       contractions has the potential to reflect, to some extent, motor unit
       recruitment changes resulting from the preceding contractions, and that
       through comparisons of M-wave amplitude parameters contributions of
       varying fibre types over the course of a contraction may be indicated.
 DE    Adult  Comparative Study  Electric Stimulation  Electromyography  Human
       Leg  Male  Middle Age  *Muscle Contraction  Muscles/PHYSIOLOGY
       Reference Values  Volition  JOURNAL ARTICLE

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