Electromyographic activity and applied load during seated quadriceps exercises

Purpose: The aim of this study was to quantify and compare mean quadriceps muscle activity and applied load for eight seated quadriceps exercises using four types of resistance. Methods: Using surface electromyography (EMG), the right rectus femoris (RF), vastus lateralis (VL), and vastus medialis oblique (VMO) muscles of 52 university students aged 23.5±3.4 yr (35 female and 17 male subjects) were examined during the exercises. Resistance devices included an ankle weight (78 N), blue Thera-Band® tubing, a Cybex® 340 isokinetic dynamometer, and an Inertial Exercise Trainer® (IET). Electrogoniometer data were collected to determine the range of motion (ROM), angular velocity, and phase (concentric/eccentric) of exercise. Load cell data were analyzed to determine tubing and IET applied loads during exercise. A within-subjects criterion was used to improve intrasubject EMG reliability. All EMG values were normalized to a 100% maximum voluntary isometric contraction. Repeated measures ANOVAs with Bonferroni comparisons were used for statistical analysis. Results: Within-subject effects of muscle and exercise were significant (P