Eleven adult males (mean
$\pm$
SD age
$= 22 \pm 3$
years) performed maximal, concentric isokinetic leg extension muscle actions at velocities of 60, 120, 180, 240, and 300
$^{\circ}\cdot$
s
$^{-1}$
on a Cybex 6000 dynamometer. The results indicated that peak torque (PT) decreased(
$p<0.05$
) as muscle action velocity increased. Mechanomyographic (MMG) amplitude increased with velocity to 180
$^{\circ}\cdot$
s
$^{-1}$
for each muscle tested (vastus lateralis
$=$
VL, rectus femoris
$=$
RF, and vastus medialis
$=$
VM). For the VL, MMG amplitude continued to increase to 240
$^{\circ}\cdot$
s
$^{-1}$
and then plateaued, while the RF plateaued from 180 to 300
$^{\circ}\cdot$
s
$^{-1}$
. The VM showed a constant increase in MMG amplitude to 300
$^{\circ}\cdot$
s
$^{-1}$
. Electromyographic(EMG) amplitude increased to 180
$^{\circ}\cdot$
s
$^{-1}$
and then plateaued for each muscle. These findings indicated muscle-specific differences in MMG amplitude patterns across velocity that may be attributable to differences in fiber type composition, muscle architecture, and/or tissue layer composition. Furthermore, these results suggested that there were muscle-specific, velocity-related differences in the association between motor unit activation(EMG) and the mechanical aspects of muscular activity (MMG).
