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A good article here...
http://espn.go.com/nfl/story/_/id/9581925/seattle-seahawks-use-unusual-t...
It was a pretty big revelation at the time and it was before the title run.
Also, they approach it from not just the athletic angle, but also the mental sharpening.
Of note, the Seahawks have a sports psychologist on staff and integral in the program.
Watching some of the boneheaded things that go on on the diamond, you'd think mental sharpening would be helpful.
However, like there are many -dos (judo, kendo, aikido, etc.), there are many ways to this end (as visible in Ichiro).
Myself, I haven't tried. Mostly it's because I'm embarrassingly inflexible.
But after reading this thought stream, I'm definitely interested.