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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, which was developed by Wilfred Bigelow, John A. Hopps, and J. C. Callahan.