Cardiac Vagal Nerve Activity During Exercise: New insights and future directions

A new paradigm is emerging in which cardiac vagal nerve activity is maintained and increases during exercise. This paradigm challenges decades of studies that have quoted a withdrawal of cardiac vagal activity during exercise. Here, we outline the existing evidence for increased cardiac vagal activity. We also explain why previous indirect methods used to measure vagal activity might have indirectly led to incorrect conclusions about the role of the cardiac vagus during exercise. We will review evidence that vagal control of the sinoatrial node and the ventricles differs and how vagal neurotransmitters other than acetylcholine may regulate cardiac function during exercise. We will also suggest future directions for research to uncover how the cardiac vagus influences cardiac function and the mechanisms behind the increase in cardiac vagal nerve activity during exercise.