They abused the hell out of it in the frieza saga, actually. Goku spent all his time on that ship hitting himself with kamehamehas then recovering from his injuries, which is how he got something like 20 times as strong on it.
Did Goku even know about that ability when he was hitting himself with those?
I know in the manga at least, Vegeta specifically tells Krillin to beat the shit out of him so that his Saiyan power thing will activate and make him powerful enough to defeat Frieza, so they seem to be aware of it. Of course, Toriyama forgets about things all the time and the plot elements of Dragon Ball are inconsistent as hell.
FAKE EDIT: Ninja'd.
He doesn't forget about it.
But as I said that power becomes either literal or figurative as the plot demands.
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Watched "Ring Ni Kakero 1" a boxing anime that is not as good as Haijime but features something completely insane and unheard of!
Someone threw in the towel for legitimate reasons! BEFORE the fight was over... in fact before they started the round.
HOLY COW!!! I've watched a LOT of episodes of sports animes and if there are three rules
1) Refs are useless
2) Coaches are useless
3) Doctors are useless
And this was a doctor who was acting as a coach!... Mama mia it is a miracle!
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Edit: NEVER FREEKEN MIND!!!
Apparently he just kicked the towel out of the ring... and he is going to stupidly continue. The doctor coach never throws it back in or anything.
So lucky that your in a sports anime and no one REALLY gets permanently injured if they are a main character (unless they start off with that injury)