Pre-exhaustion refers to performing one or more sets of an isolation, singe-joint movement prior to the performance of a compound movement. This is done to prefatigue the larger muscle so it is stressed adequately, as sometimes smaller muscles may fail before the larger muscle is fully exhausted. An example of this might be performing sets of dumbbell flyes to pre-fatigue the pectorals before doing sets of bench press, as sometimes the triceps give out before the pecs do.