Does level of load affect relative activation levels of vastus medialis oblique and vastus laterialis?

The purpose of the study was to evaluate the effect of different relative loading levels on the EMG activity of Vastus Medialis Oblique (VMO) and Vastus Laterialis (VL). Previous research into the EMG temporal and spatial relationship between VMO and VL has increased the controversy surrounding the topic, due to the majority of studies failing to be consistent in electrode placement, level of loading and subject selection. It is generally believed that the nature of the loading task will significantly affect results; despite this few studies have controlled relative load level between subjects. EMG activity of VMO and VL was measured at four load levels (MIVC, 75%, 50% and 25% of MIVC) in 10 asymptomatic male subjects. No difference in onset of activity was found between VMO and VL (p > 0.05) and onset of activity was not affected by level of load (p > 0.05). The relative level of load had a significant effect both on overall activity of VMO and VL, and the ratio of their activity. The study has shown that relative level of load can have significant effects on the parameters measured and if this variable is not controlled for within the study design it becomes a potential confounding effect.