Endurance exercise training‐induced resting Bradycardia: A brief review

Endurance exercise training is associated with a reduction in resting heart rate. The mechanisms responsible for the training‐induced resting bradycardia remain unclear. The purpose of this manuscript is to review the literature and propose a model which analyzes the components contributing to the training‐induced resting bradycardia. In addition, important training principles required to obtain the training‐induced resting bradycardia are discussed. Our model suggests that a reduced intrinsic heart rate and an altered cardiac autonomic balance in favor of parasympathetic dominance contribute to the training‐induced resting bradycardia. The reduced intrinsic heart rate may be due to the effects of an increased mechanical force and/or an altered electrophysiological and metabolic environment at the sinoatrial node. Increased cardiac parasympathetic dominance is associated with an increased cardiac parasympathetic nerve activity and a decreased cardiac sympathetic nerve activity. These adaptations require a high intensity, endurance exercise training program during an extended period.