I'm not sure if you can or should compare a human athlete with an equine one.
But take Jahvid Best - the best running back in the Pac 10 last year. He gets a concussion and they don't even let him practice .. let alone play or even suit up for a single game for the final 8 weeks of the season.
As hard as this horse (he's the 1A) hit the top of his head on the gate less than a week prior to his workout - I'm pretty surprised he didn't get a concussion.
