EMG activity of the vastus medialis oblique and vastus lateralis muscles during repeated isokinetics contractions

Abstract

The purpose of this study was to determine the effects of repeated isokinetic contraction on the EMG activities and onset timing response of the vastus medialis oblique (VMO) and vastus lateralis (VL) muscles during selected functional activities between athletes and a non-athletes group. Forty healthy males, who had no lower musculoskeletal injuries and pain,volunteered for the study. All subjects performed repeated isokinetics concentric contractions against the velocity of 60s -1until the knee extension torque decreased to 50 % of peak torque. Three functional activities: stair stepping (SS), bilateral squat (BS), and unilateral squat (US) were performed after repeated isokinetics contractions while EMG activities of the VMO and VL muscles of the subject's dominant leg were recorded. A 2x2x3 mixed model ANOVA (2 times x 2 groups x 3 activities) revealed statistically significant difference normalized VMO and VL EMG between pre-test and post-test. Similar to EMG amplitude, there was significant difference of VMO and VL onset timing between pre-test and post-test. Moreover, for VL onset timing, two main effects (time x activities and time x group) were significantly different. In conclusion, the results of the study showed that VMO and VL activities and onset times during the selected functional activities were affected by repeated isokinetics contraction which may alter patella tracking pattern