Comparison of Electromyographic Amplitudes of the Adductor Magnus Muscle among Three Different Clinical Testing Positions

Abstract

Although normalizing the EMG signals is necessary for physiological interpretation and comparison between muscles and between subjects, no EMG study has investigated the standardized position to achieve maximal contraction for the adductor magnus muscle. Accordingly, it is necessary to employ a maximum voluntary isometric contraction (MVIC) position that elicits the highest activation to increase the validity of EMG studies and provide accurate comparisons between studies. Therefore, the purpose of this study was to compare the peak electromyography (EMG) of the most commonly used positions in the literature (i.e., the fully extended hip and knee, hip-flexed 45°, and knee at 90°) to a novel position: prone hip extension with 90° knee flexion. An ultrasound imaging system was used to guide the surface EMG electrode placement on the adductor magnus (AM) muscle, for a group of ninety-four recreational runners. AM demonstrated the greatest MVIC activity in both prone and hip-flexed 45° positions with no significant differences between them (p < 0.05). However, significant differences were displayed between the AM activities while performing the fully extended hip position and the other two positions. Based on these results, it is recommended that the prone and hip-flexed 45° positions can be used to measure the MVIC of the AM interchangeably. Furthermore, the prone position can be considered to be a position of the greatest MVIC of AM, particularly when the position of hip-flexed 45° is limited as well as it can be used to quantify MVIC for both AM and hip extensor muscles simultaneously.