Reynolds said Tracy was the best coach she had ever had. “He always tells the truth,” she said. “If you ask him, ‘Well, how do you think I did today?’ he’ll tell you, ‘You had a bad race,’ ” she said. “It’s because of his honesty that when you receive a compliment from him, you know you’ve done really well, and it makes all the runners want to strive to please him.”

Until three years ago, Tracy, an accomplished runner, could keep pace with his fastest runners. Symptoms of his illness began nearly five years ago, he said, when a muscle in his thumb stopped functioning. And last June, he was found to have amyotrophic lateral sclerosis, or Lou Gehrig’s disease.

But it is only in the past year that the disease has begun to debilitate him. A.L.S. patients, most of whom eventually lose the use of all but their eye muscles, typically live three and a half to four years after the onset of symptoms, but the range can vary widely.

At the beginning of this season, Jim Ketcham, the school’s athletic director, assembled the team and told the runners that Tracy was very sick. The news devastated the team. “Everybody was crying,” Reynolds said.

Since the start of the season, Tracy’s condition has grown visibly worse. “He’s been falling down sometimes at practice,” Reynolds said. “And he brings a chair to our workouts.”