Agonist-to-antagonist dependency during target-directed isometric elbow flexion and extension.

Muscle coordination during isometric elbow contraction was investigated in this study in order to understand the agonist-to-antagonist dependency. 15 healthy subjects were recruited and instructed to perform target-directed isometric elbow flexion and extension. Electromyography (EMG) signals from both biceps and triceps were captured. Root mean square (RMS) of the EMG signals was applied to reflect the muscle activation level and fuzzy approximate entropy (fApEn) was utilized to represent the complexity of EMG signals. Mutual information (MI) was applied to analyze the inter-dependency between biceps brachii and triceps brachii. The differences in RMS and fApEn between elbow flexion and extension were non-significant. And the MI between the biceps and triceps during isometric extension was significantly higher than that during isometric flexion. Our results suggested that the lack of proficiency in using triceps may result in more dependency towards the use of antagonist during isometric elbow extension than elbow flexion.