Fast twitch recovery
My favorite exercise in spinning class goes like this: About midway through the hour when we are all well warmed up, the instructor puts on some music with a moderate beat and tells us to find a hill. Then, at intervals, more or less coordinated with the refrains, we are to pedal hard for a five-count, increasing the speed of our exertion as the count goes up, till we are pushing full-out when he says "five." Then we have a litle time for recovery, back on our hill at the same tension, for the remainder of the four or so minutes for the song.
The first few rounds of sprinting are okay, like being out on the road and trying to kick up into a passing cadence. But then my leg muscles start getting worn out, and I start to feel that lactic acid burn generated by the fast twitch fibers sorely beset, and it takes a lot of determination to put out the effort needed for the three or so seconds of peak effort. Right at the end, the thighs seem utterly spent, but the amazing thing is that they do come back around and the discomfort actually does vanish in time for the next five-count. This is nearly as exhilirating as the sprints themselves, to be shown that the rigors caused by pushing myself as hard as possible are survivable, and that the pain is not permanent. And, once again, after the class is over and we've had our stretch, I'm walking on clouds.