There is an idea declared in B.K. Frantzis's books that one should stay well within the boundaries of your limits. Well within the boundaries. Like, 60-70% of your personal limits. This is a reasonable idea. For if you regularly approach your limits, or even worse, "give 110%", then you'll be exceeding them. And that damages the body. Which throws you back health-wise or even performance-wise.
I recall this often. For modern sports certainly don't foster health. They take in the young, develop some extreme abilities, and throw people out. Most careers are over by the time you are 30. The long-term health is not a consideration in this case, just performance at all cost. The former sportsmen and sportswomen are not very healthy when they get older. And many of them die young. Newspapers are full of these "strange" occurrences if you pay attention. Here is Spanish soccer player who died when he was 26. Here is a vaulter who died in practice. Here are two runners who died in San Jose marathon. The article actually mentions another marathon death as well.
It's tragic that the deaths are happening, but the real reason is not so much of an individual desire to excel, as cultural emphasis on extreme performance. I wish the parents of would-be performers would think about their children parting with a part of their health in order to have a fleeting chance to become "number one".
Sport is not unique in this respect. Quite similar arguments can be made about fashion models and their unnaturally slimmed-down bodies. Here is a video of the models wobbly and unsteady walks. Some of them literally pray before each showing not to fall down.
In fact, parallels are abound. One can find them in yoga practitioners who stood on their heads for hours at a time, until their neck vertebrae fused together. Or in karate practitioners who damaged their hand mobility to turn them into weapons. Extremism has shortcomings. You want to get some, there will be consequences.
