Thanks Charlie!
Just one question: in your Big Circuit, what is the distance walked btween 200s? 100+200+200+100? Is plus 50m walk between 200s? Thanks
the + is a 50m walk yes, sometimes a ++ is written in, thats 100m - normally ++ is done between sets, if im not mistaken 
Yes, all +s are 50m walk with advanced athletes but a beginner might use 100m walks to achieve the goal- which is to finish at the same pace as you started with.
There is NO line.
Athlete C would be the best prepared to function “aerobically” at high intensity,hence display speed and power while consistently recovered and supported by his aerobic energy production pathways.
Extensive tempo and alactic speed (as from Charlie’s words) are one way to get there,and one very easy to manage:just appropriately manipulating the respective proportions of work according to the demands of the event and the to the needs of the individual,you can create the above described C athlete,and let him lead the way…