prefaced his masters career by winning the Golden Gate Marathon outright, with a time of 2:29:16, on a hilly course in San Francisco, California. In 1980, Heinrich ran 2:22:34, his lifetime personal best, in the West Valley Marathon in San Mateo, California, where he placed third and missed qualifying for the 1980 U.S. Olympic Marathon trials by just forty seconds. On April 21, 1980, two days after his 40th birthday, he was the first masters finisher at the Boston Marathon, with a time of 2:25:25, good for 51st place overall. Heinrich then left marathons and moved to ultramarathoning. In 1981, he set several records during a combined 50 mile/100 kilometer road race in Chicago. In the 50 mile race, his second-place finish was a new World record for masters runners. Moreover, he continued running, and in the 100 kilometer race set an absolute American record (i.e., the best of either road or track venues) of 6:38:21 for 100 kilometers. This result was also a World record for masters runners. In 1983, he set an absolute American record for the 24-hour run of 156 miles, 1388 yards in a track race in Maine. In 1984, he set an absolute American 100 mile record of 12:27:01, again in a track race. One year later, he set the American track record of 7:00:12 for 100 kilometers. In so doing, he became the only American man to hold both the road and track versions of the American record for the same event. His 12:27:01 for 100 miles and 7:00:12 for 100 kilometers still remained, at the end of 2007, the official American track records. In his career, Heinrich set American national records for any age in the standard ultramarathon distances of 100 kilometers, 200 kilometers, 100 miles, and longest distance run in 24 hours. At the end of 2007, Heinrich was inducted into the American Ultrarunning Association's Hall of Fame. In his book Why We Run: A Natural History (originally titled "Racing the Antelope"), Heinrich reflected on the sport of running as a scientist, and recounted his performance in the 100 kilometer race that began his ultra-marathon career. Combining his expertise as a physiologist, comparative animal biologist specializing in exercise and temperature regulation, and runner, he posits that the unique human capacity for long-distance running in heat is a human adaptation similar to running adaptations in other animals. Another argument of the book was