This is my opinion based on what I have been able to do where I live. I have said in an earlier post I join CF because I do not understand programming, I do not say I can’t coach.
Look at the vid from 1.00. over Saidy’s shoulder a drill is being done, it is not speed dynamics, no stepping over the knee or straightening the knee so you can paw the ground. After the start he loses control.
Call it a dynamic stretch if you want but it is a drill that I have been using on kids that the system coaches over here would not train because they were not at a high enough level, after they improved several were approached and told they were at that required level and would be coached if they asked again.
Asafa Powell’s start is in my opinion is good, what is lacking is a balance (left verses right) hence veering to the left. Look at Saidy’s start it is almost the same.
Sady, could you please tell me what school you went to, so I can make sure not to send my kids there? :D. Content aside, your punctuation is so bad it makes most of your posts a nightmare to read!