Fig. 4. Mean normalized EMGs from six dogs trotting with 2% of body mass added to each wrist (i.e. distal limb mass manipulation). For each muscle, the black line represents the average EMG when the dogs trotted on the level (control) and the grey line represents the average EMG when the dogs trotted with the added mass attached to the distal forelimbs. For each dog, the trotting speed was the same during the control and added mass trials. The error bars are the s.e.m. for each sampling bin.