Fig. 3.

Summary statement. In vivo work loops estimated for the wallaby (A) biceps femoris and (B) vastus lateralis muscles during hopping at 4.2 m s⁻¹ on a level versus at an incline. Muscle stress was estimated from inverse dynamics of joint torques to obtain muscle force and muscle fiber cross-sectional area, with fascicle strains recorded via sonomicrometry (McGowan et al., 2007).