First of all, a huge number of adrenalin promotes arterial tension which render negative things on your hurt because slow down functionality of it. And if don't want many problems with you hurt just avoid getting lots of adrenalin.
The second, when you are really often in extrime condition, you beging lose sense of dangerous, and it isn't less important than previous point. And you should think before doing.
And I know that a lot of my friends have got opposite point of view, they think that if it calls "EXTREME SPORT" it might be extreme, and there is none of this without danger, I agree with them but there is many other way to die)))
And in the end of this essay I just wanna say go in for sport, but do it without risk for anyone lives)