Could you elaborate a bit on why it's impossible to sprint downhill? I realize that you have to draw the line when the decline becomes so steep that the runner is experiencing freefall more than self-generated propulsion but I fail to see how even at relatively moderate declines sprinting faster is rendered impossible. If this is in fact true, is it that perhaps on a decline the runner is "in the air" too long whereas if he were on a flat surface he would have his feet reach the ground sooner, thereby reducing the time between each act of propulsion? (The foregoing assumes of couse that a runner is better off relying solely on his own abilitiy to generate propulsion rather than incorporating into his forward motion the greater level of momentum that naturally occurs when moving downhill.) One advantage that a flat surface might have over a decline is that, when speaking strictly in terms of covering a prescribed LINEAR distance as fast as possible, like the 100m for example, it seems the runner will actually have to travel slightly further on a decline compared to a flat surface; while both surfaces will necessitate the runner pushing off and up with each stride the decline will force the runner to travel a greater distance to reach the next point where he will make contact with suface to make his next push due to the increased distance he has to drop. Again, I don't know how significant this difference in distance really is. On the other hand, one has to consider that unchecked sprinting downhill will almost certainly result in a "lengthening" of one's stride, meaning the runner will cover more distance with each step than he would on a flat surface. I suppose the crux of the matter is which variable is more important for getting from point "a" to point "b" the quickest: waiting less time between steps to generate the next instance of propulsion and taking the marginally shorter path(flat surface) OR covering more distance with each step by exploiting the help of gravity(decline). It seems possible that, in terms of TOTAL distance covered by a runner, a runner moving downhill might cover 100 total meters faster than he would on a flat surface even though at the point that the downhill runner has covered that 100m he may have actually only moved 95 LINEAR meters.
You speak as someone who has great authority in this area, and let me say I'm not assuming you don't have such authority. This post I started was merely a thought experiment, admittedly based mostly in theory, though in my own training I have experienced what I perceived was the ability to sprint faster downhill compared to on a flat surface. You suggest that this perception is not based on an actual comparative increase in forward speed but rather the effect of gravity distoring my senses. Yours is an interesting idea and perhaps it is based in epirical evidence. Are you aware of tests that have been conducted to determine if there is any validity to this? I'm not asking sarcastically but as someone who wants to know the truth. Perhaps proof in this matter requires nothing more than a few principles of physics and actual testing is not required. I really don't know. Everything I wrote here today (and in the original post)is just me thinking out loud. No need to get chippy, old chap.
While I have an idea, I was wondering if you could also explain what "taking the piss" means?