In 1956, the Royal Canadian Air Force through Wing Commander J.K. Tett asked a civilian, William Orban to join their R.C.A.F. Recreation Branch as a civilian consultant to help them to develop an exercise plan for them. After two years William Orban and his team finalised the fitness program. They considered calling it 5 Basic Exercises Physical Fitness Programme but that was too long so it was shortened to 5BX - a ladies program followed this called XBX. Originally designed for the forces it quickly 'spilled over' to the world. Over 24,000,000 copies were reportedly sold.

The premise for 5BX came to Mr. Orban in Illinois, when he noticed his son's maximum oxygen intake did not improve significantly, even as he became more skilled on the treadmill. He also noticed that certain elite athletes -- Jesse Owens was tested in the energetics lab at the University of Illinois -- did not show improvements in their fitness levels after lengthy bouts of exercise. Perhaps length of time wasn't as important as previously thought. Perhaps the intensity of the exercise was more important.

[This is backed up now, as James writes " bouts or intervals of high intensity workouts have shown to have greater results in regards to burning fat, improve fitness and building strength."]

Hear radio interview with Wing Commander Tett (1961) ) External Link
5BX requirements (from the book MR.5BX by John J.Jackson)

The Late William Orban