THE EFFECTS OF NORMALIZATION METHOD ON ANTAGONISTIC ACTIVITY PATTERNSDURING ECCENTRIC AND CONCENTRIC ISOKINETIC KNEE EXTENSION AND FLEXION

The purpose of this study was to compare different normalization metho ds of electromyographic (EMG) activity of antagonists during isokineti c eccentric and concentric knee movements. Twelve women performed thre e maximum knee extensions and flexions isometrically and at isokinetic concentric and eccentric angular velocities of 30 degrees . s(-1), 90 degrees . s(-1), 120 degrees . s(-1) and 150 degrees . s(-1). The EMG activity of the vastus lateralis, rectus femoris, vastus medialis and hamstrings was recorded. The antagonist integrated IEMG values were n ormalized relative to the EMG of the same muscle during an isometric m aximal action (static method). The values were also expressed as a per centage of the EMG activity of the same muscle, at the same angle, ang ular velocity and muscle action (dynamic method) when the muscle was a cting as an agonist. Three-way analysis of variance (ANOVA) designs in dicated significantly greater IEMG normalized with the dynamic method compared to the EMG derived using the static method (P<0.05). These di fferences were more evident at concentric angular velocities and at th e first and last 20 degrees of the movement. The present findings demo nstrate that the method of normalization significantly influences the conclusions on antagonistic activity during isokinetic maximum volunta ry efforts. The dynamic method of normalization is more appropriate be cause it considers the effects of muscle action, muscle length and ang ular velocity on antagonist IEMG. Copyright (C) 1996 Elsevier Science Ltd.