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

The purpose of this study was to determine the velocity-related patterns for mechanomyographic (MMG) amplitude, electromyographic (EMG) amplitude, mean 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. Twelve adult women (mean +/- SD: 22 +/- 3 years of age) performed such leg extensions 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) across velocity to 240 degrees /s. MP and MMG amplitude for each muscle (VL, RF, and VM) increased (P < 0.05) with velocity to 240 degrees /s and then plateaued. EMG amplitude increased (P < 0.05) to 240°/s for the VL, remained 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 similarities between the velocity-related patterns for MMG amplitude and MP, but dissociations among EMG amplitude, MMG amplitude, and PT. These findings support the recent hypothesis that MMG amplitude is more closely related to MP than PT during maximal, concentric, isokinetic muscle actions and, therefore, may be useful for monitoring training-induced changes in muscle power.