Fig. 2. Muscle force, fascicle length and power output for the lateral gastrocnemius, LG, and peroneus longus, PL, muscles in a turkey running at a steady speed of 2 m s^–1 on level ground. Shaded areas are stance, when the foot is in contact with the ground; unshaded areas are swing, when the foot is off the ground and being repositioned for the next step. L, fascicle length; L₀, resting segment length.