Reciprocal coactivation patterns of the lateral and medial quadriceps and hamstrings during low- and moderate-speed isokinetic movement

The purpose of this study was to examine coactivation patterns of the lateral and medial quadriceps and the lateral and medial hamstrings during low- and moderate-speed isokinetic movements. Twelve female athletes performed isokinetic knee assessments at 60 and 180 degrees/s. Root mean square electromyographic (rmsEMG) activity and the median frequency of the EMG (mfEMG) were determined by placing bipolar surface electrodes on the vastus lateralis (VL), vastus medialis (VM), biceps femoris (BF), and medial hamstrings (MH). Results of rmsEMG indicated that the VM showed almost twice the coactivation of the VL (p < .05), and that the BF showed almost four times the coactivation of the MH (p < .05). Finally, differences were noted in the mfEMG (p < .05), with the VM displaying different recruitment patterns at 180 degrees/s as an agonist compared to that as an antagonist. Results indicated that when acting as antagonists, the VM and BF display the greatest EMG patterns during isokinetic knee joint movement.