Glenn Cunningham, a former world-record holder in the mile run who in 1979 was named the greatest track performer in the history of Madison Square Garden, died yesterday. He was 78 years old. That Mr. Cunningham could win 21 of 31 mile races on the indoor track at the Garden during his prime in the 1930's was impressive. More significantly, he did it after suffering life-threatening burns on both legs as a 7-year-old when a stove in a school classroom in Everetts, Kan., exploded, killing his older brother Floyd. After being told there was a strong possibility he would never walk again, he spent seven months in bed, and then received daily massages from his mother, who kneaded his damaged muscles and sped his way to walking, and then running. In high school, he played baseball and football and boxed and wrestled. At 13, he entered his first high school mile race and won easily. Using running as therapy for the burn injuries, he found that middle distances suited him. At a sophomore at the University of Kansas, Mr. Cunningham set an American record for the mile with a time of 4 minutes 11.1 seconds. He was selected as a member of the United States team for the 1932 Olympic Games in Los Angeles, and finished fourth in the 1,500-meter run. In 1933 he won the Sullivan Award as the nation's top amateur athlete. In his competitions at Madison Square Garden, Mr. Cunningham set six world records in the mile and the 1,500 meters and another at 1,000 yards.