Figure 4).

The severity of ventricular arrhythmias in control dogs (filled histograms) and in dogs subjected to treadmill exercise 24 h previously (open histograms). In the exercised dogs, the number of ventricular premature beats (VBPs) and both the incidence and the number of episodes of ventricular tachycardia (VT) are markedly reduced. Compared with the controls, in which 40% of the animals fibrillated during occlusion, no dog in the exercised group died during the same occlusion period. Furthermore, greater than two-thirds of the dogs subjected to exercise survived the combined ischemia-reperfusion insult, in contrast to only 10% of the controls. VF Ventricular fibrillation