Electromyographic Analysis of Moderate Sustained Isometric Exercises for Vastus Medialis Components

Document Type : Original Article

Abstract

Strengthening of the oblique portion of the vastus medialis muscle (VMO) by moderate isometric exercises, 
particularly at the early phase of rehabilitation program for acute knee injury is an important part of knee 
rehabilitation protocols. The goal of this study was to investigate whether moderate sustained isometric 
exercises at level of 20% and 30% MVC activate the oblique portion of the VMO to a significantly greater 
extent than longus part (VML) of this muscle. Nine healthy men with no history of knee injury were tested;
Multi-channel surface EMG signals were recorded from vastus medialis oblique and vastus medialis longus of 
the right leg during 70-s isometric contractions at 10%, 20% and 30% of the maximal force using controlled 
laboratory study. Average Rectified Value (ARV) and Mean Power Frequency (MPF) computed from the 
surface EMG were significantly increased with contraction intensity for both VMO and VML muscles (P < 
0.05). However, the rate of change over time in ARV and MPF were significantly greater for VMO than VML 
(P < 0.05). Moderate sustained isometric exercise at 20% and 30% MVC was effective in activating the medial 
stabilizer of the patella, and therefore, it may be used at the early phase of rehabilitation program to establish 
patella control as stable base for knee rehabilitation.

Keywords

• vastus medialis oblique, EMG, muscle activation, moderate sustained isometric contraction
• fatigue

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