Indoor riding allows for special concentration on technique and form, because one does not have to concentrate simultaneously on navigation, terrain, other vehicles, weather, rules of the road, rollerbladers, walkers, dogs, children, and other objects that make cycling complicated. It’s just the machine, the TV and/or iPod Shuffle, and me.
Just now I am working on the positioning of my knees and the movement of my feet. Both of these technical issues seem predetermined by the fact that my feet are always on the pedals and when I push the pedals with them my knees just follow along. But it turns out that the closer my knees come to the top bar of the bike (within reason) the better. Not only is it more aerodynamic, but also this position delivers the maximum force to the pedals with least effort, since the knees stay directly in line with the pedals. Keeping them there requires something of a knock-kneed pose, which fortunately is my natural disposition. My heels remain just slightly outboard of my toes when my feet are on the pedals. In fact, if the knees are too far away from the top bar, it probably means that the saddle height is insufficient, like a grownup riding a child’s tricycle.
As for circles: it’s all about the pedaling motion. Most novices stomp on their pedals on the downstroke. But serious riders have had clipless pedals since the mid-eighties, and toe clips before that. The purpose of these devices is to attach the rider’s shoes to his or her pedals. That means that when one foot pushes down on a pedal, and the other pedal moves upward, the upward moving foot, attached to the pedal, can “pull” the pedal up, just as the downward moving foot can push the pedal down. Thus the ideal pedal motion is not to “stomp” on the downward pedal, but to pedal perfect circles with both feet, neither stomping down on the forestroke nor letting up on the backstroke. Just apply equal pressure with both feet as the pedals rotate in perfect circles. The increase of power in relation to effort is enormous. On an outdoor bike it involves having judgment, knowing the “feel’ of your feet, and not trying to force the issue in training.