Fig. 8. Three-dimensional force fields produced by the monoarticular hip flexors (A) (iliacus internus, ILi, top row; iliacus externus, ILe, bottom row), the hip adductor muscles (B) (adductor ventral head, ADv, top row; sartorius, SA, bottom row) and the knee flexor muscles (C) (semitendinosus, ST, top row; iliofibularis, ILf, bottom row). ST is for the combined action of STv and STd. Force fields were constructed as described in Fig. 7 and in the text. The peak force produced at each of 80 positions is plotted. The force field produced by each muscle is normalized to the maximum force within each field so that force fields can be compared among muscles. The left columns of A (hip flexors), B (hip adductors) and C (knee flexors) show a top view and the right columns show a side view of the frog and the muscle force fields. One block in each view represents 10 mm², i.e. line divisions are 10 mm in length. Each muscle produced force fields that were a combination of elevation—depression, rostral—caudal and medial—lateral functions (see text). The magnitude of the force vector components produced by the contraction of each muscle was configuration-dependent.

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