Prince Philip was spry and walking without a cane right up until he died at 99 in April. What kept him walking tall? It was probably 5BX, the original functional fitness routine. Standing for Five Basic Exercises, it’s an 11-minute workout created for the Royal Canadian Air Force in 1956. “[It] is designed to show you how to develop and hold a high level of physical fitness, regardless of where you are located,” reads the introduction booklet to the workout. “The 5BX Plan puts physical fitness within reach of every member of the RCAF.” Several sources report the Duke of Edinburgh completed the simple regime of equipment-free exercises on a daily basis—the workout even made an appearance in an episode of The Crown , a Netflix series about the reign of Prince Philip’s wife, Queen Elizabeth II. Shutterstock Canadian Bill Orban developed the routine based on research he conducted at the University of Illinois in the 1950s. By testing oxygen intake he realized duration of exer...