Pre-exhaust / post-fatigue
This method implies that you select 2 exercises for the same muscle group. As the name implies, fatigue the target muscles in this technique before or after the main exercise itself (usually a basic exercise). This happens in each case through an additional isolation exercise.
You should use this technique of pre-exhaustion, if you cannot really exhaust the target muscles with your usual go-to main exercise, because the other involved (synergistic) muscle groups are already limiting you in your ability to perform. An example would be bench press, in which the triceps give up before the chest. In this case, you complete a set of pec deck or dumbbell flyes beforehand and then move on to bench press.
The post-fatigue method pursues a different goal. In this case, the target muscle group (e.g. the chest) fails first in the main exercise. However, the goal is now to fatigue beyond this point. Therefore, you should aim for isolation exercises that do not involve the arms as much to avoid performance drops for later exercises and sets. Also here, pec deck or dumbbell flyes can be performed, but this time after the main exercise.
Classic combinations include:
- leg extensions with squats / leg press,
- butterfly / fly with bench press in all variations,
- front / side / rear raises with shoulder press,
- stiff-legged deadlift with leg curls or
- lat pull-over with pull-ups / pull-down.
Of course, other combinations exist and are just as feasible. Your imagination here can be virtually unlimited.
Pre-exhaust automatically means that the training weights for the main exercise must be lower. Do not let your ego confuse you and incite you cheat on the movements. The goal here is the intensity and stress on the target muscles, not about personal strength records or a competition with your training partner.