Endurance Training Reduces Risk of Sudden Death
A new study looked at the possibility that exercise training can decrease cardiac sympathetic activity and could, thereby, reduce beta-receptor responsiveness and decrease the risk for ventricular fibrillation, or sudden death.
Dogs that received a 10-week exercise program saw a reduction in beta-receptor responsiveness which prevented ventricular fibrillation, while those dogs that were sedentary either died or suffered ventricular fibrillation that was treated.
You’ve probably heard of beta blockers: medication that blocks the action of epinephrine and norepinephrine on the β-adrenergic receptors in the body (primarily in the heart, peripheral blood vessels, bronchi, pancreas, and liver). The hormones and neurotransmitters stimulate the sympathetic nervous system by acting on these receptors. Activation of beta receptors by epinephrine increases the heart rate and the blood pressure, and the heart consumes more oxygen. Drugs that block these receptors therefore have the reverse effect: they lower the heart rate and blood pressure and hence are used in conditions when the heart itself is deprived of oxygen. They are routinely prescribed in patients with ischemic heart disease and hypertension.
With this study, it is evident that exercise also attenuates beta-receptor activity and reduces the risk of cardiac arrest.