This phrase seems to have passed out of the modern athletes vernacular, but in my day, I’ve heard athletes talk of a “second wind” where they feel a little rejuvenated after exercising for a while.
Is there some physiological explanation for a “second wind”?
IMHO – there is some justification for it. There are 3 distinct engergy sources for athletics produced by the human body. I can’t think the names of them off-hand, but they are distinguished more for the time periods they are good for. There’s very short-term energy (like sprinting), medium (“normal”), and long-term (marathoning and such). If you exercise, at some point one source of energy will fade and (hopefully) another will start taking over. That seems like it might account for the “second wind”.
Then there’s the role of stretching and warming up, but I know even less about that!
I’m putting my money on endorphins.
http://www.proteamphysicians.com/patient/perf/endorphins.asp
or
http://www.shesgotsports.com/runningarticle.shtml
Muttrox has pretty much got it.
The deal is that when you begin exercising you get your energy from anaerobic (non-oxygen) systems. It takes a few minutes for your aerobic systems, such as the Krebs Cycle (remember first year bio?) to crank up.
So it takes around 12-15 minutes for your “wind” to get in gear. Some trainers and coaches have a trick they use, which is to tell their clients/athletes to just jog or swim or whatever for the first 15 minutes, and then they can stop if they feel exhausted. Well if you move at a moderate pace for that long, you WILL feel better because your aerobic systems have begun producing the bulk of your energy.