Thanks for your reply, CouchWarrior, The Muay-Thai Roundhouse must generate tremendous power, either that or that guy's bones must be thin from cancer. Why did that guy have such a weak shin? I saw on the "Fight Science" video that a Muay-Thai's shins get lots of bone strengthening from repeated practice striking on the bags.
By the way, I know that girl is not showing a Mauy-Thai kick. It's a Karate Kick. But it appears to be faster than a Mauy-Thai style. If the Mauy-Thai is always so slow, and if the defense is as easy as lifting your knee, then why bust your shin?