[Kaizer007]

I'm sorry to have misrepresented my skepticism on the subject. I was not trying to make any point or mute point. My only inquiry was about acceleration.
You did point out that the negative acceleration would be off the charts when running into a lamp post and it would be much higher than a normal runner would be used to. Also it could not be measured by means in a foot race.
My objection is that infinity could not be reached negatively or positively in the real world.
A bullet, for example, stops instantly to our eyes, but it starts instantaneously to our eyes as well, and your argument stated that the ramp up is true, but not the ramp down. Even if it could not be measured, wouldn't logic state it couldn't get to be an infinite instantaneous stop if the runner hits a lamp post and just a very negative slope?