Keith Burgess-Jackson, J.D., Ph.D.

The best measure of overall fitness, to me, is resting heart rate. The average person has a resting heart rate of 72 or so. I began recording my resting heart rate 24 years ago today. I record it every other Wednesday, in similar conditions: while sitting quietly at my desk, first thing in the morning, before coffee. My average resting heart rate in the past 24 years (608 readings) is 51.06. It was 47 nine days ago, when last I checked it. The lowest I've ever recorded is 42 (three times). The lowest I've ever heard of is 27: Swiss cyclist Mauro Gianetti, before the start of the 1997 Tour de France. (Riders are given physical exams before the Tour starts.)