Fig. 8. Sample electromyographic signals of the external (A) and internal (B) oblique muscles recorded during running on the level, uphill and downhill. These recordings are from a 34kg dog running at 2ms^-1. They illustrate the different patterns displayed by the external versus the internal hypaxial muscles. In each graph, the horizontal bars represent the period of support of the left hindlimb. Compared with running on the level, activity in the external oblique muscles decreased when the dogs ran uphill and increased when the dogs ran downhill. In contrast, the internal oblique muscles displayed the opposite pattern.