I am not a big fan of pre-exhaust training but for an occasional change of pace, this is a really intense way to go. The principle behind the concept is that the smaller muscle groups in any compound movement will give out first; the reason being simple in that the weaker muscle will always give out first in any given exercise. It does make sense
For example, when doing bench press; it is the triceps and shoulders which will fail before the chest muscles. Even after having gone to total failure on the bench press, in reality, your chest still has some gas in the tank left. Following that line of thought, it really becomes difficult to truly take a major muscle group to total failure. What gives out first during chins, your biceps or your lats?
Back when Arthur Jones was pushing his nautilus equipment and his training philosophy, he argued that pre-exhaust was critical to muscle growth. During the mid to late 70’s, Mike Mentzer become the ambassador for this training concept to the general bodybuilding world.
Mike Mentzer, and his brother Ray, essentially claimed that the popular six day split routines doing 4 to 5 exercises per body part with up to 30 sets were actually counterproductive and an idiotic way to work out. It was quite a controversy at the time, culminating in the showdown between Mentzer and Schwarzenegger at the 1980 Mr. Olympia contest.
Part of Schwarzenegger’s return was to demonstrate the superiority of his methods versus Mentzer’s. After the contest, Mentzer basically went away, as far as competitive bodybuilding went. He was a tad disillusioned.
But back to Mentzer’s pre-exhaust methods; Mike (let us be on first name basis) advocated supersetting an isolation movement with a compound movement to truly punish the muscle. What he wanted to do was to create a situation where the smaller muscle was temporarily stronger than the major muscle. So that instead of the chest muscles pushing the triceps to failure; it is the triceps pushing the Pecs to failure.
So he recommended that you do a set of bench flyes which pretty much isolates the chest muscles first. Immediately following that set (with zero rest); Mike would instruct you to plunge right into a set of bench press. Right at that moment, as you start your bench press; theoretically, you triceps are stronger than your chest muscles. Triceps would be fresh and being the stronger muscle, it will not fail before the chest muscles.