Abstract
The purpose of this investigation was to use electromyography (EMG) combined with pattern classification procedures to examine differences in activation among the superficial quadriceps femoris muscles during fatiguing concentric isokinetic muscle actions. Ten men (mean ± SD age=22.4 ± 1.2 yrs) and six women(mean ± SD age=23.0 ± 2.1 yrs) performed 50 consecutive maximal concentric isokinetic muscle actions of the dominant leg extensors at a velocity of 180°/s. During each muscle action, bipolar surface EMG signals were detected from the vastus lateralis (VL), rectus femoris (RF), and vastus medialis (VM). These signals were then processed with a wavelet analysis, and the resulting intensity patterns were classified using pattern classification procedures. The results demonstrated that the EMG intensity patterns could be separated into muscle-specific groups with rates ranging from 89–100% and classified with accuracy levels between 84% and 100%. These findings showed muscle-specific activation patterns in the quadriceps femoris muscles, despite common femoral nerve innervation. These differences in activation likely reflected the different roles of each muscle during leg extension. Future studies need to be done to further examine these differences during other activities that include movement at the hip joint, such as running and cycling.