I know you said on general but I think it is worth pointing out that MIT doesn't specifically mark any athletes for admission like most schools can and do. At least when I applied.

I knew a varsity crew and varsity sailing athlete and despite both being nationally notable in their sports my understanding was the coaches could do nothing to "recruit" them. It of course helps in admission as much as playing a music instrument at a high level or being a published author might. If you have that plus elite academic achievements then you probably have a decent chance at admission to a school of your choosing.