Fig. 2.

Muscle-tendon models. (a) Elementary tendon-muscle-tendon fiber (TMTF) units. (b) TMTF units in unipennate arrangement. OT, ET: origin and end tendon sheets. F: fascia. (c) Two unipennate muscles, not necessarily of the same size, stacked back-to-back, form a bipennate muscle. The unipennate ET fuse into a bipennate ET. (d) Model of (c) reversed: bipennate OT gives rise to two unipennate muscles. (e) Multipennate or multisegmented muscle, formed by stacking unipennate models back to back.