Dave graduated from Overbrook High School in 1933. He found the ideal sport for his great size and strength by becoming a heavyweight weightlifter. He finished second at the 1936 U.S. senior nationals. That same year, he won a position as a member of the United States Olympic weightlifting team. At the Berlin Olympics, Dave competed in the heavyweight division and finished in 12th place.

In 1937, Dave won the U.S. heavyweight weightlifting championship with a total lift of 835 pounds and was named “America’s Strongest Man.” Due to his size, strength and reputation, he had a brief stint as a professional wrestler. Mayor went to work for the York Bar Bell Company and became a regional director. He believed in weight training for all sports and helped initiate what was believed to be the first weight training program in professional football for the Dallas Cowboys. The strength of the Cowboys program became the talk of the NFL and other teams began to follow their example. Dave later took his weight training skills to Philadelphia’s Vesper Boat Club, and the Club won the Olympic Gold Medal in 1964.

Dave was the coach of the U.S. Weightlifting team in the 1960 Maccabiah games in Israel. He was the President of the Middle Atlantic district of the Amateur Athletic Association (AAU), and served as Director of the U.S. Senior National AAU Weightlifting Championship. He was also a founder and President of the B’nai B’rith Sports Lodge in Philadelphia.