Mike Mentzer's training system
Mentzer was originally an advocate of pre-exhaustion weight training. For example, leg extensions are done before squats, side delt raises before shoulder presses, flyes before bench presses, and stiff-arm pulldowns before standard lat pulldowns. Mentzer was also famous for going "beyond failure" with forced reps, negative reps, static holds, and forced negatives.In general, one only used 1-2 sets per movement, with no more than five movements per muscle group.
After renewing his training business in the 1990s, Mentzer became convinced that even the relatively low-volume routines advocated by Arthur Jones and himself were, in fact, too exhausting for average trainees. Mentzer later advocated a build-up routine involving two leg workouts, one pec-delt workout, and one lat-bicep workout every 10-14 days.
After the trainee' results plateau, he switches to an advanced system involving a very brief full-body workout, to be followed once every 6-10 days. Some Mentzer pupils report training each muscle group only once every 21 days.
Mentzer and advocates of "high intensity" training believed that one must train very hard, using the heaviest weight one can manage in good form and without injury. In general, high intensity trainers eschew the use of Olympic lifts, Olympic lift derivatives, explosive or ballistic lifts of any kind, and plyometric drills.
In general, high intensity advocates believe the opinion of Jones, that while strength can be increased by 400% in an average individual, recovery capacity can only be increased by 50%. Therefore, the stronger one becomes, counterintuitively, the less one must train.
PS - I haven't been able to locate a specific routine of Mentzer that uses the principles outlined above.