It’s precisely because of the pain, precisely because we want to overcome that pain, that we can get the feeling, through this process, of really being alive- or at least a partial sense of it. Your quality of experience is based not on standards such as time or ranking, but on finally awakening to an awareness of the fluidity within action itself.
Haruki Murakami discussing triathlons in What I Talk About When I Talk About Running, a memoir of sorts by the Japanese writer/runner. He gets at the core of what athletic activity can represent- a chance to fully channel experience through the body, letting all thoughts, save total awareness of the moment, completely fade away.