>>508741798To put a finer point on this, each time a cell divides to repair damage, the DNA strand also divides. An enzyme rebuilds each daughter cell's strand. Each time the DNA divides, a piece is torn off each end. This would be catastrophic if the bits torn away were information, but they're actually repeating, non-coding TG sequences, and there are about 100 of them (the image above says 50, but that's wrong) When the cell that works perfectly fine detects that there are only a few telomeres left at the ends of the DNA it is containing, it refuses to divide. So this means that as we grow older, the majority of our cells can no longer repair damage. This is why our bones become brittle, our skin wrinkles, our spines bend, our eyesight dims, and eventually the flu can knock us off.
Bodybuilding is deliberate tearing of muscle tissue in order to cause it to come back stronger, which is to say more muscle tissue replaces the damage. These people are literally shortening their lifespan by years just to bulk up. Not incidentally, so are surfers whose skin must repair solar damage repeatedly. And boxers who get the shit kicked out of them regularly.
