Originally Posted by
79pmooney
Usually, you go over the bars because your front wheel has slowed. So , unless the fork crumples, the bike has little choice but to pivot over the slower moving wheel. Your head goes forward, yes, roughly parallel to the ground, but the bike seat goes up, taking your butt with it. Now your butt is higher than it was and has more potential energy to impart to your head when it slows as it contacts the ground.
I think the easier way to think about it is dispersal of kinetic energy. The lowest impact crash is a low-side, because almost all the kinetic energy is dispersed by sliding (RIP skin).
When you OTB, your front wheel has locked but your kinetic energy is still within you. So it gets changed to rotational energy with the front wheel as a pivot. Now when you hit the ground, you’ll hit it dead on. No sliding. All the kinetic energy is going to get dispersed by your skull, teeth, shoulders etc.