Pre-fatigue – a method of training, the essence of which is to fatigue the target muscle in advance (or muscle groups) with the help of isolating exercises, after which they pass to performing basic exercises. For example, you perform simple crossovers, directing the load directly to the pectoral muscles, then proceed to a fairly heavy bench press. Another option – leg extension and squat with the bar on the shoulders, that is, presses with the feet. Theoretically, it's good, but practically it's not quite like that. In theory, this method works best for those muscle groups that are power and which "punch" through basic exercises is very difficult. This method works least efficiently in the case when neither isolating nor basic exercises can direct the load exactly to the right place.
"Double split" is considered another variation of the method of pre-fatigue. This approach to building a training program, in which the load is given to a previously tired target muscle group. As Charles Polikvin argued, the biggest effect comes if you train the same muscle group 2 times a day (morning and evening) or 2 a day in succession. The same is evidenced by the experience of schools of bodybuilding from the Baltic States. Back in those years when the Soviet Union existed, the Baltic athletes achieved the maximum increase in the volume of the muscles of the hands by training them for 2 consecutive days.
Indeed, in this case, it is possible to attract the maximum number of muscle fibers to work, due to a strong pre-fatigue. But even in this case the best result will be shown by those muscles, which before were power. It is necessary to find a way of training that will allow you to train all the desired muscle fibers and in those muscles that are lagging behind.