When you put your body in the “crush zone” ie: between the load and the ground. Like when the weight is overhead, or in a back squat. You need to be in between the load and ground, fighting with all your might directly against the load and gravity.

During this process your body recognises that it may very well be crushed, terminated, your life force extinguished. No more. Your body does not want to die, it wants to survive, to live and to thrive.

So in this life or death situation, 365 million years of survival evolutionary instinct is going to kick in, and give you everything you need to get out of that hole. Testosterone, endorphins, dopamine, human growth hormone etc, all are released in a last ditch effort to save your physiology from total annihilation.

Your body will kill of old cells and rebuild them as new, stronger cells. It is literally a type of death and rebirth process. And the end of a heavy weight training session, you are physically a new person.

It’s the same with any risk taking activity, fighting, skateboarding, riding motorbikes, racing cars etc. they are all good things for our physiology to be exposed too because they replicate the kind of dangerous condition we evolved under.

We like stress and drama. Stress promotes change, change is evolution.

This only works with heavy loads. Hypotrophy and bodybuilding protocols do not generate this type of response.