[quote author="Jeremy Richmond" date="1253937487"]Explosive starts are very tiring on the quads for which the strength is essential during top speed running (to prevent collapse of the knee – maintain stiffness). If the focus is on top speed running then you will want to spare the energy in the quads so that you can execute a sufficient number of quality top speed reps (steps).
Of course a fly in from a slight hill would help the exercise more.
So, to prevent your quads from tiring, how should the run-in be done?[/quote]
I am not an expert on the subject but…
I have found that fly-ins do not get me the same degree of top speed running as those emanating from a sprint start. I would like to use a standing crouch position with something that the arms can use to help propel forward or a hill for some free acceleration. The savings are not much – perhaps only an extra 5m of top speed running by not getting up from a block start.
From personal experience the best top speed running was achieved from drop-jump or more likely drop-to-sprint starts from a height equivalent to the optimum drop-jump height.