Why training "chest" isn't enough
Most programmes treat the chest as one muscle. It has four distinct regions, and the flat bench only really loads one of them.
If your chest day is bench press, incline press and a fly, you are training one region hard and two barely at all. The pectoralis major is not a single sheet of muscle that contracts uniformly.
The four regions
The clavicular head runs from the collarbone and responds to incline pressing. The sternal head, the bulk of the muscle, does most of the work on a flat press. The costal fibres near the bottom are best reached with a decline or dip. And the full-range function — bringing the arm across the body — needs a fly or a cable crossover.
Train all four in a session and you get balanced development. Train one and you get a chest that looks impressive from exactly one angle.
What balanced actually looks like
One movement per region, three to four sets each. That is twelve to sixteen working sets, which is more than most people need in a single session — so rotate the emphasis week to week rather than doing all four every time.
Javix does this automatically: when you pick a chest day, it distributes your exercises across every region and flags the one that has fallen behind.