Ultrasound Evaluation of Mechanical Properties of Individual Muscles-Tendons during Active Contraction

A new method to accurately measure the mechanical properties of individual muscles and tendons under active contraction is presented. An individual muscle is activated selectively to different intensities through electrical stimulation with adjustable amplitude, frequency, and pulse width. During the course of active contraction of the stimulated muscle, muscle fiber pennation angle, muscle fascicle length, tendon length are measured by ultrasonography in vivo and non-invasively. The force produced by the stimulated muscle is derived from the measured joint torque and the moment arm recorded by a 3-D motion tracking system. The relationship between the force produced by the selected individual muscle and the muscle and tendon architectural parameters are studied quantitatively for the flexor carpi ulnaris and flexor carpi radialis.