Pacemaker

A pacemaker is a competitor who enters an athletics race with little or no intention of winning, but purely to set a fast pace for other competitors to follow.

The heart pacemaker is a group of cells within the heart that together initiate contractions and set the pace of beating. For most people, this is a group of cells in the right atrium of the heart, otherwise known as the sinoatrial node[?].

Also related to the heart, "pacemaker" is the common term for an implantable artificial pacemaker device.