The science behind all this is pretty simple honestly.

When you shout you have to inhale first, and that act of inhaling gives you a burst of muscle power. But when you also combine that with a loud exclamation or a shout or curse, you actually startle yourself on some level. Your brain listens to you, always remember that. So when your brain hears you shout or scream, it drops everything and goes into survival mode. IE: a burst of adrenaline.

When you combine adrenaline and oxygen you can do almost super-human things like smash cinderblocks with your bare hands and lift cars off trapped people.

If you want to try charging your muscles for something strenuous like opening a tight jar lid, you can skip the cursing and shouting and just take three deep breaths, and on the last breath draw it in as fast and hard as you can and hold it for a moment as you try to exert the force, it will feel astonishingly easier.