What does it take to have superhuman strength?

It takes a lot of power and energy to have superhuman strength. Imagine lifting up hundreds of pounds of weight. That would need a lot of energy and almost unlimited use of muscles. In reality, that would be hard to have but in our dream worlds, our sense of good and benevolence would make us use our strength for good purposes.

adrenaline and a stressful situation.

Explanation:

in your everyday life, your brain holds back most of your strength as to stop you from hurting yourself. in stressful situations, your brain lets go and allows you that strength and releases adrenaline in order to give you the energy to use that immense, superhumanly strength, in order to achieve its goal, your survival. this is a simplified answer but it's what I can give you. I'd suggest skimming the article in case they touch on other topics and information.