Fig 4 -

In (A) the lateral view of the experimental setup in form of an anatomical sketch is shown. An ultrasonic probe (SP) is used to image a cross-section of the distal part of the upper arm. The cross-section contains the distal tendon of the biceps brachii (BicT). Simultaneously, the force generated by the arm is measured with a force sensor (FS) near the wrist (cmp. Fig 3). The biceps brachii (Bic), its long head (BicLH), its short head (BicSH), brachialis (Bra) and humerus (Hum) are also labeled. In (B) the ultrasonic images of two orthogonal cross-sections are depicted. The orientation of both imaging planes are marked in a sketch on the right side, which shows the anterior perspective on the Bic and Bra. Orientation I was the only imaging plane used during the presented study (cmp. (A)). The structures of the Bic are marked in red. The junction of Bic and BicT was observable in this view (white cross) as well as part of the aponeurosis (BicAP). Imaging plane II is orthogonal to imaging plane I. The furcation (wing-like structure) of the aponeurosis was observable (marked in orange) as well as different parts of the Bra muscle group—the brachialis deep head (BraDH) in green and the brachialis superficial head (BraSH) in blue.