Fig. 2. Muscle action potentials during running over flat versus rough terrain. (A) Recordings of the muscle action potentials (MAPs) activating the ventral femoral extensor (179) in the hind left leg of a cockroach running on flat (black trace) and rough terrain (blue trace). Each cluster of spikes occurs during a single stance phase. Changes in neural stimulation would necessitate neural feedback in the control of locomotion over the rough terrain. (B) Four measures of the activation burst describe the degree of stimulation (number of spikes) and the relevant timing parameters (interspike interval, interburst interval and burst phase).