http://www.youtube.com/watch?v=Pw05h_hcQ_4
Thankyou “christravis” for the link and pointing out the rear block issue:
For those who still advocate no force against the rear block in the start, check 3min 15sec into the above link to see the rear block collapse under pressure in Usain Bolt’s lightning start in his 1st round of the 100m at the 2011 World Championships in Daegu. He turns at around halfway to see where Dwayne Chambers is and then jogs the last half of the race. A man against children! Watch for Bolt’s “step-over” action and how soon he gets into this preferred position and how well he sustains this action throughout his race, qualifying fastest for the semis into a headwind.