Quantifying EMG and VMG muscle patterns during a maximal effort isovelocity, isometric and isotonic leg extension movement

The purpose of this study was to investigate the use of electromyography (EMG) and vibromyography (VMG) to quantify the normalized amplitudes of the rectus femoris (RF) and vastus lateralis (VL) muscles during the concentric portion of an isovelocity, isometric and isotonic leg extension movement. Twenty-eight-university aged participants, 19 males and 9 females, in good to excellent condition volunteered to be included in this study. The participant characteristics were: (mean ± S.D.) age, 22.8 ± 5.6 yr; height, 174.1 ± 8.8 cm; and body mass, 78.0 ± 13.6 kg. All participants were familiarised with testing protocols and pretested on a Biodex isokinetic dynamometer to determine their resting and normal isokinetic, isometric and isotonic contraction values. Participants performed in random, a peak effort for three isokinetic contractions at 60 degrees/s, a 5-s isometric contraction, and a peak isotonic leg extension lift. Surface EMG electrodes and a VMG piezoelectric accelerometer were affixed to the RF and VL muscles of the dominant leg during data collection. A series of one-way ANOVA's revealed significant (p < 0.05) differences between EMG and VMG values for the three leg extension tasks. Significant linear correlations were found between peak isokinetic torque expressed in bodyweights and mean VMG (r = 0.448), and between peak isometric torque expressed in bodyweights and peak VMG (r = 0.348). These data will help guide exercise selection for individuals with differing training objectives and injury history. This study also demonstrates that VMG is a better discriminator of muscle force values between subjects and contraction type.