A Possible Molecular Basis of the Change in Load Sharing Between Synergistic Muscles Characterized by Elastography

Muscle contraction is mediated by the formation of cross-bridges between heads of myosin and active sites of actin filaments. In this sense, skeletal muscle can be conceptualized as a receptor-ligand complex and can exhibit cooperative and non-cooperative binding behavior during contraction. In the present work, from estimates of the shear elasticity of biceps brachii, brachioradialis, and brachialis, we found different kinetic behavior (hyperbolic or sigmoid) during the isometric flexion of the elbow joint. The above could determine their specific contribution to the increase of joint torque by varying the percentage of maximum voluntary isometric contraction. We suggest that this type of mechanism could underlie the load sharing between synergistic muscles at the molecular level.