Is a "second wind"--getting back into things after feeling tired out--something that actually happens with the body, or is it all in the mind? Or some combination? Not every ride where I feel beaten up ends up on a positive note as I finish reasonably strong with a second wind. There are times when I just limp home, sometimes doing as little as 10 MPH on flat ground (and not into a headwind). But a second wind has happened on enough rides that it got me wondering, especially after I felt a second wind yesterday on a century ride.

Some SoCal BikeForums members were on a Sunday century where we went out harder than we intended, and so fatigue really started setting in on the way home. I started feeling it at around mile 75, and for the next 15 miles, my performance got worse and worse. The pace of my dragging myself home more or less stabilized by mile 90 and even started improving a bit, but there was a 6% grade (for 400 vertical feet) at mile 95. Oddly, as the climb went on, I felt better, and I felt really good on the last few miles after the climb. Any signs of cramping or other hurt had gone away, I could cruise at 20+ MPH again (as opposed to about 14 MPH a few miles earlier), and even more surprisingly, I had the ability to accelerate reasonably hard, something I really hadn't done for the last 20 miles.

Surely some of that must be psychological. Being a few miles from the end with no climb of note left, I could no longer concern myself with whether I would make it home, and thus I could go at it hard without consequences. But at other times, I've gotten a second wind on an unfamiliar route, far from the end of the ride. One occasion last month had me feeling pretty bad after a short but steep grade at mile 45 and considering abandoning from miles 55 to 70--didn't mostly because I couldn't since I was in the middle of nowhere--yet feeling okay from mile 70 to the end at mile 125. Never really fully recovered from the hurt the grade at mile 45 of the ride had put me in, but after recovering a bit (while riding) I settled into a consistent and reasonable tempo for the last 55 miles. Another occasion last September had me feeling pretty bad from about mile 40 to about mile 55, yet feeling pretty good from mile 60 to mile 90, and feeling great for the 35 miles after that. Indeed, for that last stretch, it was the best I've ever felt on a bike.

Is it all mental? If so, can sheer willpower allow one to avoid the painful middle stretch before the second wind kicks in? Is there a real physical second wind? If it's physical, is there some way to get it to kick in earlier?