Analyse des sollicitations musculaires via la technique d’élastographie «supersonic shear imaging»

Study of muscle contraction using elastography. Due to limitations of electromyography (EMG), the implementation of complementary methods to quantify muscle contraction levels in vivo would provide very interesting information for the study of muscle coordination. Thus, after a basic review of elastographic methods for the study of muscle contraction, the aim of this short review is to present recent works from our group that aim at assessing the accuracy of the technique called supersonic shear imaging (SSI) to estimate muscle contraction level. In a first study, a strong correlation was found between muscle shear elastic modulus and EMG activity level for the biceps brachii muscle during isometric elbow flexions. Then, this result was used to analyze the coordination of the four main elbow flexors, including the deep muscle that can not be studied using surface EMG. This study showed a change in the load sharing between brachialis and biceps brachii muscle during incremental isometric elbow flexions. This change could explain, at least partially, the wellknown non-linear relationship between EMG and torque for the biceps brachii. Finally, preliminary results showed an excellent correlation between the shear elastic modulus and joint torque during isometric contractions that implies only one muscle (i.e., the first dorsal interosseus and the abductor digiti minimi that produce at least 93% of index and little finger abduction, respectively). These results showed that individual muscle force could be estimated from shear elastic modulus measurements performed by SSI. Considering the scientific and clinic relevance of muscle force estimation in vivo, interesting research perspectives can be envisaged