Vince -
1. I concur w Dr. Chimps. It is the duty of a theorist to prove his/her theory. You're wrong until proven right.
-bb doc
Wrong, the correct way is to falsify the theory. Carl Popper (science philosopher) gave a very good example of the pitfall of trying to prove theories:
All swans are black. You can prove this every time you see a black swan but when the 121.745.876th swan is white, the theory goes bottoms up. (BTW, competing theories can coexist on the same continuum, as they might hold true under different conditions.)
That doesn't mean that someone can make any claim they want and get away with it. A study that yields certain results can be used to formulate a hypothesis or theory. New, similar research will try to emulate the results (and fail ideally) to disprove the previous study.
Where vince's logic fails is that he takes intensity as a constant. He then proceeds to say that it isn't the intensity that makes the ultimate difference. The problem is that it's impossible to measure or controll intensity. Levels of intensity and intensity perception vary hugely between subjects, so it's the intensity that would actually be something worth studying.
It simply comes down to making the muscles do something that they have not experienced before. That will require them to adjust in a couple of ways: The muscle becomes more efficient and will grow a bit. After a short period of training a muscle will be close to it's maximum efficiency and most of the adjusting will be in the form of growth. Different muscles will react differently to different stress. The calves are very much a slow-fiber aerobic muscle group. Using added weights on your normal walking can slowly build them, that is the same idea as vince's constant stress concept. The pecs are different, short but heavy workouts have greater effect here. More volume like doing a lot of pushups will grow them but only initially and not that much.
I think intensity is the key to succes. It's the last 5% of the excercise that makes the difference, the first 95% is just working your way to that point.