Fig. 1. Anatomy of the lateral gastrocnemius (LG) and digital flexor-IV (DF-IV) muscles in the guinea fowl hindlimb, illustrating the sites of transducer implantation. Forces were measured from the common gastrocnemius (G) tendon and the tendon to DF-IV (inset) via tendon buckle force transducers. Note that the guinea fowl does not possess independent free tendons to the lateral and medial heads of the gastrocnemius. Muscle fiber length changes and muscle activity were measured in the LG and DF-IV (inset) of the left hindlimb using sonomicrometry and electromyography, respectively.