In regards to the question of the Running A’s serving as a substitute for the special endurance, my view is that this is a far less optimal alternative in comparison to a split run. If the second rep of a 300m is not in the cards then go for 150 + 150, or 200 + 100 or what have you in order that the biodynamic activity is still the run yet the split aspect will provide for higher quality for those athletes who do not yet possess the special work capacity to perform the 300m repeats.