On a more serious note, I recommend reading on VO2max by Matt Fitzgerald http://mattfitzgerald.org/ and other of his articles. But this one especially caught my attention, on how VO2max affects performance, in brief, it is not everything but it helps. Also the long time belief that long distance runner cannot be the best sprinter and vice versa does hold some truth, but training on speed does improve endurance.

Put aside the scientific test and proof, for long distance runner like me, somehow I know for sure I need bigger lung capacity to last longer, and also maintaining at a constant speed is as equally important. So this artcle does explain abit why, and I like the way he uses analogies and examples for simple minded reader like me, though I still had to read a second time to understand.

Simply, it is the maximum amount of oxygen that one can take in per minute, V is the volume, O2 is the oxygen, or rather dioxygen (2 atoms of oxygen) exist at standard temperature and pressure, max is just maximum.

There is a site to measure your VO2max - http://health.drgily.com/walking-test-peak-aerobic-capacity.php

My VO2max is 33ml/kg/min VO2max, suffering an average mortality risk.