This raised a question: If all the latest cutting-edge scientific research says that outdated barbell movements have to be updated with core stability tricks and then integrated into super-short high-intensity muscle-confusion routines, how come none of that did much for me, while the same five lifts repeated for a year caused profound structural changes to my body?
The answer, it turns out, is that there are no cutting-edge scientific studies.
Those plans works for the same reason Mr. Rippetoe’s protocol works: The human body is an adaptation machine. If you force it to do something a little harder than it has had to do recently, it will respond — afterward, while you rest — by changing enough to be able to do that new hard task more comfortably next time. This is known as the progressive overload principle. All athletic training involves manipulating that principle through small, steady increases in weight, speed, distance or whatever.