People conceptualize conditioning in different ways," he said. "Some think it's a ladder straight up. Others see plateaus, blockages, ceilings. I see it as a geometric spiraling upward, with each spin of the circle taking you a different distance upward. Some spins may even take you downward, just gathering momentum for the next upswing. Sometimes you will work your fanny off and see very little gain; other times you will amaze yourself and not really know why.
John L. Parker Jr., Once a Runner
motivational, running, workout