And proper pedaling technique. Before learning to spin, I set my saddle to the 108% formula as mandated by Eugene Sloane's Complete Book of Bicycling and mashed my knees into oblivion. I thought it was because my bike was too small.

After a break from the bike I started training with a racing club. The saddle came down and back, gearing came down and the feet turned faster. Forty years later, when I injure my knees, doing things like running too much, skiing, or peeling off climbing walls, cycling is part of the therapy. And I'm still riding the same size bike.