title: M-wave potentiation after voluntary contractions of different durations and intensities in the tibialis anterior.
abstract: The study was undertaken to provide insight into the mechanisms underlying the potentiation of the muscle compound action potential (M wave) after conditioning contractions. M waves were evoked in the tibialis anterior before and after isometric maximal voluntary contractions (MVC) of 1, 3, 6, 10, 30, and 60 s, and after 3-s contractions at 10, 30, 50, 70, 90, and 100% MVC. The amplitude, duration, and area of the first and second phases of the M wave, together with the median frequency (Fmedian) and muscle fiber conduction velocity (MFCV) were recorded. Furthermore, twitch force, muscle fascicle length, and pennation angle were measured at rest, before, and 1 s after the conditioning contractions. The results indicate that only the amplitude of the second phase of the M wave was significantly increased after conditioning contractions. The extent of this potentiation was similar for MVC durations ranging from 1 to 10 s and augmented progressively with contraction intensity from 30 to 70% MVC. After these conditioning contractions, the duration and area of the two M-wave phases decreased (P < 0.05), whereas MFCV and Fmedian increased (P < 0.05). For all of these parameters, the greatest changes occurred 1 s after the conditioning contraction. Changes in MFCV after the contractions were correlated with those in M-wave second-phase amplitude (r(2) = 0.42; P < 0.05) and Fmedian (r(2) = 0.53; P < 0.05). In contrast, fascicle length and pennation angle did not change after the conditioning contractions. It is concluded that the potentiation of the second phase of the M wave is mainly due to an increased MFCV.
authors: Department of Electrical and Electronical Engineering, Public University of Navarra, Pamplona, Spain; javier.rodriguez.falces@gmail.com.
authors: Javier
authors: J
authors: Rodriguez-Falces
authors: Laboratory of Applied Biology, ULB Neuroscience Institute, Université Libre de Bruxelles, Brussels, Belgium; and.
authors: Jacques
authors: J
authors: Duchateau
authors: Department of Education, Meisei University, Tokyo, Japan.
authors: Yoshiho
authors: Y
authors: Muraoka
authors: Laboratory of Applied Biology, ULB Neuroscience Institute, Université Libre de Bruxelles, Brussels, Belgium; and.
authors: Stéphane
authors: S
authors: Baudry
mesh_terms: D000200:Action Potentials; D000328:Adult; D004576:Electromyography; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000502:physiology*; D014463:Ultrasonography; D055815:Young Adult
keywords: conduction velocity; electromyography; muscle architecture