Mechanomyographic amplitude and mean power output during maximal, concentric, isokinetic muscle actions

The purpose of this study was to determine the velocity-related patterns fo r mechanomyographic (MMG) amplitude, electromyographic (EMG) amplitude, mea n power output (MP), and peak torque (PT) of the superficial muscles of the quadriceps femoris (vastus lateralis [VL], rectus femoris [RF], and vastus medialis [VM]) during maximal, concentric, isokinetic leg extensions. Twel ve adult women (mean +/- SD: 22 +/- 3 years of age) performed such leg exte nsions at velocities of 60 degrees, 120 degrees, 180 degrees, 240 degrees, and 300 degrees /s on a Cybex 6000 dynamometer. PT decreased (P < 0.05) acr oss velocity to 240<degrees>/s. MP and MMG amplitude for each muscle (VL, R F, and VM) increased (P < 0.05) with velocity to 240<degrees>/s and then pl ateaued. EMG amplitude increased (P < 0.05) to 240<degrees>/s for the VL, r emained unchanged across velocity (P > 0.05) for the RF, and increased (P < 0.05) to 300<degrees>/s for the VM. The results indicated close similariti es between the velocity-related patterns for MMG amplitude and MP, but diss ociations among EMG amplitude, MMG amplitude, and PT. These findings suppor t the recent hypothesis that MMG amplitude is more closely related to MP th an PT during maximal, concentric, isokinetic muscle actions and, therefore, may be useful far monitoring training-induced changes in muscle power. (C) 2000 John Wiley & Sons, Inc.