Both increase size . Heavy weights by increasing fiber size . Increasing intensity by extending set through partials or rep tempo/ duration of set cause hyperplasia or fiber splitting . Past decade studies in Japan , Germany and USA have validated this . Never before did bodybuilding type studies confirm many of our old concepts and principles. Partials or cheat reps or strip sets , preexhaustion sets all fall into that. Since the body thrives on homeostasis, it makes sense to constantly change stimulation to avoid stale periods . Don’t get stuck doing same thing for months . Hence the term cycle or periodization. If it works great continue for while then change aspects go back to it again . I personally have a rotation as change is the only consistent principle I employ . Age 52 B.B. and martial arts over 30 years. Can’t live without.