THE EFFECT OF JOINT ANGLE ON ELECTROMECHANICAL DELAY IN THE VASTUS LATERALIS

Abstract

1056 The purpose of this study was to determine the effect of joint angle on electromechanical delay. Twelve adults (10 males and 2 females; age = 23.2 ± 2.2 yrs) performed maximal isometric muscle actions of the quadriceps femoris on a CYBEX II isokinetic dynamometer at joint angles of 30, 60, and 90° below horizontal. Electromyographic (EMG) and mechanomyographic (MMG) signals were recorded from the mid-portion of the vastus lateralis using a bipolar surface electrode arrangement and piezoelectric contact sensor, respectively. The time delays between the onset of the EMG signal and torque (TQ) production, the onset of the MMG signal and TQ production, and the EMG and MMG signals were measured at each joint angle. (Table)TableThe peak torque at the 60° joint angle was significantly (p<0.05) greater than that at 30 and 90°. There was a significant (p<0.05) decrease in the EMG-TQ delays between 30 and 90° as well as the MMG-TQ delays between 30 and 60°. There were, however, no differences (p>0.05) in the EMG-MMG time delays between joint angles. Thus, the length of the vastus lateralis may affect the time interval that separates the onset of the electrical (EMG) and mechanical (MMG) components from torque production during an isometric muscle action, but not the time delay between the electrical and mechanical events.