Fig. 3. Mean EMG activity traces from two trotting dogs, one from the treadmill and one from the trackway. In both cases, mean activity data for a single locomotor cycle are repeated so that the general pattern may be more easily seen. (A) Mean EMG activity traces calculated from 20 consecutive cycles of locomotion from a dog trotting on the treadmill at 2.5ms^-1. All EMG data are from muscles on the animal’s left side. Mean footfall diagrams are shown below the EMG energy traces, with rectangles indicating periods of support by the indicated foot. The cross-hatched boxes highlight the temporal relationship between muscle activity and ipsilateral rear foot support. (B) Mean EMG activity traces calculated from 15 locomotor cycles from a dog trotting along a trackway at a speed of 2.0ms^-1. All EMG data are from muscles on the animal’s right side. Mean footfall diagrams are shown below the EMG activity traces, with rectangles indicating periods of support by the indicated foot. The cross-hatched boxes highlight the temporal relationship between muscle activity and ipsilateral rear foot support.