 While Mike Mentzer served in the US Air Force, he worked 12-hour shifts, and then followed that up with 'marathon workouts' as was the accepted standard in those days.In his first bodybuilding contest, he met the winner, Casey Viator.Mentzer learned that Viator trained in very high intensity (heavy weights for as many repetitions as possible, to total muscle fatigue), for very brief (20–45 minutes per session) and infrequent training sessions.