LEG FLEXION ANGLE AND MECHANOMYOGRAPHIC RESPONSES TO ISOMETRIC MUSCLE ACTIONS

Abstract

369 The purpose of this investigation was to examine the effect of leg flexion angle on the relationship between mechanomyographic (MMG) amplitude and isometric torque production. Nine adult males (X age=24.2 yrs) performed isometric muscle actions of the leg extensors at 25, 50, 75, and 100 percent maximal voluntary contraction (%MVC) on a calibrated CYBEX 6000 isokinetic dynamometer at 25, 50, and 75 ° below full leg extension. A piezoelectric MMG recording device was placed over the mid-portion of the rectus femoris. Separate two-way repeated measures ANOVAs (%MVC by leg flexion angle) and Tukey post-hoc comparisons were used to analyze the torque (Nm) and MMG amplitude (mV) data. The results of the investigation indicated that at 25° of leg flexion, MMG amplitude increased up to 100%MVC. At 50 and 75° of leg flexion, the MMG amplitude increased up to 75%MVC, but did not change significantly (p > 0.05) between 75 and 100%MVC. At 75 ° of leg flexion, however, the MMG amplitude plateaued between 75 and 100%MVC. These findings indicated that the MMG amplitude-isometric torque production relationship was leg flexion angle specific. It is hypothesized that torque-related differences in muscle stiffness were responsible for the leg flexion angle specific patterns in MMG responses. FigureFigure