But Mr. Marchand was amenable. A diminutive 5 feet in height and weighing about 115 pounds, he said he had not exercised regularly during most of his working life as a truck driver, gardener, firefighter and lumberjack. But since his retirement, he had begun cycling most days of the week, either on an indoor trainer or the roads near his home in suburban Paris.

Almost all of this mileage was completed at a relatively leisurely pace.

Dr. Billat upended that routine. But first, she and her colleagues brought Mr. Marchand into the university’s human performance lab.

They tested his VO 2 max, heart rate and other aspects of cardiorespiratory fitness. All were healthy and well above average for someone of his age. He also required no medications.

He then went out and set the one-hour world record for people 100 years and older, covering about 14 miles.

Afterward, Dr. Billat had him begin a new training regimen. Under this program, about 80 percent of his weekly workouts were performed at an easy intensity, the equivalent of a 12 or less on a scale of 1 to 20, with 20 being almost unbearably strenuous according to Mr. Marchand’s judgment. He did not use a heart rate monitor.

The other 20 percent of his workouts were performed at a difficult intensity of 15 or above on the same scale. For these, he was instructed to increase his pedaling frequency to between 70 and 90 revolutions per minute, compared to about 60 r.p.m. during the easy rides. (A cycling computer supplied this information.) The rides rarely lasted more than an hour.

Mr. Marchand followed this program for two years. Then he attempted to best his own one-hour track world record.