title: Mechanomyographic responses to concentric isokinetic muscle contractions.
abstract: The purpose of this investigation was to examine the effects of velocity of contraction on the mechanomyographic (MMG) responses to maximal concentric isokinetic leg extension movements. Eight adult males [mean (SD) age, 22.3 (1.3) years] performed maximal leg extensions on a calibrated Cybex 6000 dynamometer at velocities of 60, 120, 180, 240, 300, and 360 degrees x s(-1) x MMG responses were detected by a piezoelectric recording device placed over the vastus lateralis muscle. Intraclass reliability correlations ranged from R = 0.84 to 0.97 and from 0.90 to 0.99 for peak torque and MMG amplitude values, respectively, with no significant differences (P > 0.05) between the mean values for test versus retest at any contraction velocity. There were significant differences (P < 0.05) in peak torque at all velocities except 240 [135 (27) Nm] versus 300 [127 (27) Nm], and 300 versus 360 degrees x s(-1) [115 (37) Nm]. The mean MMG amplitude at 60 degrees x s(-1) [61 (67) mV] was significantly less (P < 0.05) than that at 360 degrees x s(-1) [452 (451) mV]. These results indicate a velocity-related dissociation between MMG amplitude and peak torque. Furthermore, it was hypothesized that the increases in MMG amplitude were due to velocity-related decreases in muscle stiffness which allowed for greater muscle fiber oscillations.
authors.affiliation: Center for Youth Fitness and Sports Research, School of Health and Human Performance, University of Nebraska-Lincoln, 68588-0229, USA.
authors.forename: T K
authors.initials: TK
authors.lastname: Evetovich
authors.forename: T J
authors.initials: TJ
authors.lastname: Housh
authors.forename: J R
authors.initials: JR
authors.lastname: Stout
authors.forename: G O
authors.initials: GO
authors.lastname: Johnson
authors.forename: D B
authors.initials: DB
authors.lastname: Smith
authors.forename: K T
authors.initials: KT
authors.lastname: Ebersole
mesh_terms: D000328:Adult; D004576:Electromyography; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D007700:Kinetics; D008297:Male; D009068:Movement / Q000502:physiology; D009119:Muscle Contraction / Q000502:physiology*