APONEUROSIS LENGTH AND FASCICLE INSERTION ANGLES OF THE BICEPS BRACHII

Magnetic resonance images and ultrasound images were used to examine the architecture of the distal biceps brachii muscle in 12 unimpaired subjects. The distal biceps brachii tendon continued as an internal aponeurosis that spanned 34 +/- 4% of the length of the biceps brachii long head muscle on average. The distal muscle fascicles inserted at angles to this aponeurosis; fascicles anterior to the aponeurosis inserted at a significantly greater (p <= 0: 05) angle (17 degrees) than the fascicles posterior to the aponeurosis (14 degrees) in the distal 2 cm of muscle when the elbow was extended. Mean fascicle insertion angles were on average 3-4 degrees greater with the elbow flexed 90 degrees against a 5% maximum voluntary contraction load as compared to their values with the elbow extended. These data provide the basis for designing experiments to measure muscle and tendon motion in vivo.