Also spoilers for season 1 and 2. You've been warned.
The backstory of Boku No Hero Academia
Boku No Hero Academia plays in a world where the human bodies have developed to a much more streamlined version and at the same time developing uncanny abilities known as quirks. By the time the story plays 80% of the population have quirks. These quirks go from producing nitroglycerin sweat that can be made explode to being able to do whatever a frog does to producing fire and ice as well as superpower or invisibility and many more.
How One-For-All Works
Well, I warned about spoilers already so let's start with the story of this quirk. One of the first quirks that came to be was All-For-One. This quirk allowed the owner to take and pass quirks. The person who had this quirk had a brother who had no apparent quirk. So his brother gave him a quirk that allowed him to stockpile power. Surprisingly his brother did have a quirk that is useless on its own. The ability to pass on his quirks. This ability combined with the stockpile ability and created a new quirk, One-For-All. From here on out One-For-All has been passed down stockpiling the abilities from one person to another person. In the anime, the quirk is given from the number one hero All Might to the main character Midoriya or Deku.So that's the history of it, All Might also mentioned that One-For-All is an augmentation-type quirk. So let's look at how it operates for Deku and Allmight.
Many of the reporters, news as well as other people think of All Might and Deku having some kind of super strength or super speed, in the case of All Might even invincibility. Understandably so as they both increase their speed and strength when using One-For-All. Looking at Deku specifically it's important to analyze the animation. When Deku uses One-For-All focusing all on one body part, the body part starts to glow pink to red and there are veins shown lighting up. Another interesting fact is that All Might starts smoking whenever he's swapping to his buff version or vice versa. Some more information that we get is the idea of focusing the power on a body part. The word focus plays a huge role here. In the anime, it's even said that the energy is focused. If something contains a lot of energy it's particles increase in speed. Faster particles result in more collision, more collision then again results in friction, which produces heat. If something reaches even higher energy it may even emit photons of light. This is what makes the body parts look glowing red, especially since compared to All Might Deku is not able to contain the immense amount of energy in his body. Heat reacting with the air also results in the air heating and the body cooling which can result in vapor or even smoke depending on the water contained nearby, explaining Allmights smoke. Even the training with Gran Torino shows Deku having green lightning appear occasionally around his body as well as his body emitting some kind of light. All these elements show One-For-All being pure energy that is added upon the human's energy thus augmenting any ability even quirks if quirks are available. So what happens when One-For-All is passed on to the next person? It will contain Midoriya's energy as well.
One-For-All in Real Life
Quirks don't exist in real life, not as they do in the anime, however, something can definitely be taken from this anime and I can tell this from experience. Whether or not you believe me is your thing. When I was a child I thought that lying down and focusing on a part of my body or a state could heal it up faster. Surprisingly it at least felt like it would really work. Funny thing is this came naturally for me. I've kept this ability through my teens using it to amplify attacks when playing with wooden stacks (I'm sorry for breaking your self-made wooden sword with a normal stick, Robert) and I'm still able to focus energy on certain body parts as a young adult. So while it's not a stockpiling ability and I don't think, making anyone eat my DNA will give them my power, with enough practice it should work to reproduce at least... let's say 0.01% of One-For-All or something. Hey, One-For-All in the anime is way too strong, even 5% is already way stronger than anything considered above average. Unfortunately, I did not go through the training regime Deku went to. I'd consider myself more like a mob from Mob Psycho 100 than an All Might.
Gran Torino's Training
So one of the realizations Deku made in his internship at Gran Torino is not calling upon One-For-All but making it a part of himself. The idea behind this is to just have the power active at all the time having it part of his whole body instead of just one part. So the goal of this exercise is to focus not on one body part but to focus on the whole body. This gave the idea for me to try it myself. I already could focus energy on one body part so all I had to do is apply the same procedure to multiple body parts.
Applying the Theory
The first try was a total success at first, except that I lost focus after moving just a little like the way it felt changed. Next, I repeated the procedure and this is what I noticed. As it's shown in the anime Deku must be a natural. The concept behind it is simple and it's easy to get it to work when standing or sitting still (when not moving basically). However, in real life moving with this is not as easy and here's why.
Damn You Physics...
If you paid attention during physics you may know that if you want to jump for example you have to apply a force to the ground to gain an opposite force that accelerates you, right? Now if you're focusing energy on your whole body and you try to move or jump you will most likely lose the balance of energy as you automatically start to apply energy and/or the focus to the affected or required body parts to apply the force required to do the movement. Now I'm just human I don't have One-For-All it's not a big issue for me, but if Deku would focus on his whole body to split the 5% of One-For-All and he moves or jumps and applies the energy he may easily focus much more heavily on the body parts required to produce the opposing force for acceleration. The result of this would be applying a higher amount than 5% in the worst case it will result in him damaging himself.
So that's why I said he's a natural.
What's the Result?
In the anime, Deku increases his strength and speed using 5% of All-For-Ones capability. Implementing the same principle in real life seems to increase precision in movement. You can reduce unnecessary movement, the senses related to touch seem to be sharper and it seems to improve the strength and force applied to the surrounding area also affecting movement speed. It comes with a drawback though. If not trained it actually may hurt.
I know I can only say that it seems to do these things I haven't been able to use it long enough to notice definite effects and I haven't trained it enough to know the results of that.
Regardless this is gonna stay on my list longer.
