Check out this powerful story over at Aeon by Rebecca Ruiz:

It's a late summer day in 1998 during pre-season training for the women's soccer team at Seattle University. I'm 17 years old, a freshman fullback on the up-and-coming National Association of Intercollegiate Athletics (NAIA)team. After a lackluster start, I'm working to prove myself. I've let nerves shake my confidence and I can see both my coach and fellow teammates look at me as if to ask why I'm here at all.

We're doing a drill and I'm standing with my back to a lanky senior. Another player is poised to send me a pass from 10ft away. This exercise should be simple: don't let the senior steal the damn ball from behind. She towers above my 5ft 5in frame and throws her bony elbows. I get low and try to cut off her angle. The ball comes sliding into my feet and suddenly she loses her balance and lurches forward into my back. I fall face-first toward the ground. My chin absorbs the impact of my body and hers.

The grass and goals are spinning when I stand up. My vision is laced with black spots. It is alarming, but I make an athlete's calculus, measuring these symptoms against the need to show some grit to this skeptical audience. After a brief break, I rejoin practice. Passes and players ricochet past me and I can't get anywhere quick enough. I can't read plays as they unfold. The black spots linger. I've slammed my brain hard against my skull.

About 250,000 young athletes are treated annually in an emergency room for a sports-related concussion. Those with the luck to avoid our fate fear that it is only a matter of time before an off-kilter tackle or mid-air collision comes for them, too. They know that a concussion can cause lasting damage, forcing them to choose between their brain and being a competitor who refuses to quit.