SAN DIEGO — Don Pellmann had been at the San Diego Mesa College track for less than an hour Sunday morning and had already moved his lawn chair twice to remain in the shade, which was receding fast. By the time Pellmann set his fifth age-group world record, in the early afternoon, the temperature on the track was creeping toward 100, which also happens to be the birthday Pellmann recently celebrated.

Pellmann, the most senior athlete in the San Diego Senior Olympics, became the first centenarian to break 27 seconds in the 100-meter dash and the first to clear an official height in the high jump. He also broke records for men in the 100-and-over age group in the shot-put and the discus and set a record in the long jump.

Wearing baggy shorts and a faded red T-shirt with “Donald Pellmann Established 1915 Milwaukee, WI” written across the front, he opened his program by trying to become the oldest man, by roughly nine years, to record a height in the pole vault. He dislodged the bar three times at 3 feet 1 ¾ inches, which gnawed at him the rest of the day.

“I thought I was in better shape,” he said.

The meet volunteers, composed of students from San Diego State’s nursing program and Mesa College’s track team, were awed by Pellmann’s fitness level. They sought him out between his events to express their admiration.