What muscle groups do Push-ups and Pull-ups work?

It's 'lore', but some lore is reliable. This one isn't; it's a MYTH. Of course, somebody small, or skinny, has further to go in order to be massively built, than somebody who is bulky when they start training.

But that just means that you might need to train for fifteen years in order to build as much mass as the bigger guy achieves by only training for ten years. Depending on your own genetics, you might find that your body responds really well to training, and you can grow muscles rapidly. That has nothing to do with your size.

Some small guys are 'hard gainers', other small guys seem to get bulky if they just look at a dumbell. But training is also 'specific'. So you might find that you gain strength quickly, but are unable to gain bulk.

Or you might gain speed easily, if you train for it, but find training for power very slow. If you don't train appropriately for a particular type of development, you can easily form the impression that your body 'doesn't do' that type of gain.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.