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. Author manuscript; available in PMC: 2013 Dec 6.
Published in final edited form as: J Biomech. 2010 Jan 25;43(6):10.1016/j.jbiomech.2009.12.017. doi: 10.1016/j.jbiomech.2009.12.017

Fig. 1.

Fig. 1

Top view of the 2-joint, 6-muscle biomechanical arm model. Y-axis is anterior. Movements occur in the sagittal plane with no gravity, as sliding across a frictionless tabletop. Antagonistic muscle pairs are as follows, listed as (flexor, extensor): monoarticular shoulder muscles: (A: anterior deltoid, B: posterior deltoid); monoarticular elbow muscles: (C: brachialis, D: triceps brachii (short head)); biarticular muscles: (E: biceps brachii, F: triceps brachii (long head)). φ1 and φ2 are shoulder and elbow joint angles, respectively.

Adapted from (Lan, 1997). Moment arm values: d1 = 30 cm, d2 = 50 cm.