The old Second City routine comes to mind... "Blowed 'em up good." "Yep, blowed 'em up real good!"
So, yesterday I was out on a ride of pretty moderate intensity, and did a couple of all out attacks on two short hills. The second I hit spinning as fast as I could under the circumstances (120rpm), and crested it as fast as I would using my normal technique. My heart rate went higher than it would have using my normal technique, within 4 bpm of my fastest-ever observed heart rate. It was a short effort, about 60 seconds. And I blew! Afterwards, my legs weren't particularly tired, but my energy level went out the window.
Which got me wondering, does anybody know what happens, physiologically, when you blow up?