Fig. 3. Ensemble averages of electromyographic (EMG) activity of the external intercostal muscle. The pattern of bursting in uncoupled breath averages is similar in all dogs, and its relationship to ventilation reveals an inspiratory function for this muscle. The pattern of activity averaged relative to the stride is more variable, but a clear bursting pattern is present, indicating a locomotor function. Samples are from four dogs (A—D), and the average across four dogs (E), with ventilatory (bold lines) and acceleration (thin lines) traces to reveal relationships to breath and stride (F). IF indicates ipsilateral forelimb support and CF contralateral forelimb support in the footfall bars at the bottom. All traces are on the same time scale. Exp., expiration; Insp., inspiration.