First you feel strong and sprint of like you are being followed by a herd of mad cows. However, about half a minute later, you start feeling out of breath and you feel oncoming pain in your legs and another few seconds later the pain in your legs has risen to the unbearable as the lactic acid accumulates, so you have no choice than to ease off a little, but just enough so that the pain is bearable and keep at that effort till the 3minutes is over. It is in these 10 seconds of total pain from when your legs are full of lactic acid to when you ease off a little that I ask myself why am I doing this to myself?
There's also a Wikipedia entry about lactic acid.
I also had to do a few 1min flat out efforts today, these go like this: pedal like you are being followed by the "Infected" for 1min, then recover. And you know how these feel? They start is quite similar to the VO2 max drill, only that you go harder from the start and when the pain rises into the unbearable, you DON'T ease off..... which means that at 15 seconds to go your eyes start going cross, at 10 seconds to go you think you are going to fall off the bike, at 5 seconds to go you think your legs are going to explode and the last second feels like the hardest pedal stroke you have ever done in your whole life.
And yes, you've done it correctly when you feel like you want to give up competitive biking just after the drill ends...
So I guess the difference between world champ level and local champ level (if having comparable genetic disposition - ah the old nurture vs. nature argument) is just about who goes furthest in preparing your body and mind, you know, doing all those little things like pushing yourself this little bit further, turning that pedal one more time even when you think you can't, not eating that tasty triple chocolate muffin and not partying till late at night. However, there is also something sickly rewarding in enduring all these pains and sufferings, you do appreciate lack of pain and just chilling out, eating a piece of chocolate and drinking a glass of wine soooo much more.