The principle of pre-exhausting a muscle during training to me makes a lot of sense. It basically relies on the theory that in order to make a muscle grow or improve you need to take that muscle past the ‘point of failure’. The point of failure is where the muscle cannot perform any more repetitions and has ceased to be able to lift the weight in the manner that you want. This is achieved by doing multiple repetitions with a heavy enough weight or by doing multiple sets until the muscle is fatigued enough. If the muscle doesn’t reach the point of failure it is likely that it has not been worked hard enough. If the muscle has more to give in regards to performing reps then there is still room to exercise so this should be capitalized on.
Pre-exhausting basically means to exhaust the target muscle you want to work by doing isolation exercises before you move onto compound exercises. To explain further I will give you an example. Lets say we want to work the chest. Most people will start on bench press or a compound movement and then go onto flyes or pec deck or some isolation type exercise to work the pecs further. On bench press however your pecs wont reach the point of failure because your triceps and shoulders may fatigue long before your pectoral muscles will. This means that your pecs are not getting a proper workout from doing bench press. IF however you do an isolation exercise like flyes first, your pectoral muscles will be fatigued and tired before you perform the bench press. Then when you do bench press it is far more likely your pecs will reach the point of failure before your triceps and shoulders which are not fatigued at all.
People may argue the point that if a muscle is pre-exhausted then you cannot lift as much on the compound exercise and therefore wont grow as much. However in my opinion gaining muscle is not about how much weight you lift but about how hard the muscles work. The pecs will work much harder on the bench press if you have already done flyes compared with if you do it first even with a heavier weight. The triceps will have less of a workout but this is what we want really.
There have been many advocators of pre-exhausting over the years. One of the most famous was mike mentzer. He trained differently to just about everyone else past or present. He pretty much tore up the rule book and made a new set of rules that worked for him. He still managed to create a fantastic physique with it though.
I recommend trying some pre-exhausting training on each bodypart for at least a period of 4 weeks. I personally feel you will see a difference and will feel the benefit of the training. The only thing I will say is that you must leave your ego at the door. You cant be worried about lifting big weights as your strength on compound lifts will not be as great. Don’t let this dishearten you as I said before, it isn’t about how much weight you lift but how hard the muscles work.