Comparison of the EMG Activities in the Vastus Medialis Oblique and Vastus Lateralis Muscles During Hip Adduction and Terminal Knee Extension Exercise Protocols

The purpose of this study was to compare the electromyographic (EMG) activities in the vastus medialis oblique (VMO) and vastus lateralis (VL) muscles during two open chain exercises commonly used in the management of patellofemoral pain syndrome (PFPS). Twenty-five (14 female and 11 male) healthy subjects participated in the study. The A 2 (testing condition) x 2 (exercise type) x 2 (gender) quasi-experimental design was employed. Using surface electrodes, the EMG activities in the VMO and the VL muscles during ten repetitions of hip adduction and terminal knee extension exercises were recorded. The order of presentation of the experimental conditions was randomized. The three-way repeated ANOVA revealed no significant main effects for testing conditions, exercise type or gender, but the terminal knee extension exercise type x gender interaction effect was statistically significant (F= 8.28, p<.001). During the terminal knee extension exercise, the EMG activities in the VL muscle of the male subjects were higher (p<.05) than in the VMO muscle. For both genders, no significant difference was found in the EMG activities of both muscles during the hip adduction exercise. Our results revealed that neither of the two exercise methods was more effective in activating the VMO or VL muscles. Further studies are needed to identify the most effective exercise protocol for strengthening the quadriceps femoris of patients with PFPS. KEY WORDS: electromyography (EMG); quadriceps femoris; hip adduction and terminal knee extension exercises