You may have heard this – “Make smooth pedal strokes” or “Pull up on the back side” or “put pressure on the pedals.” All helpful. BUT have you thought about the size of the circle? Probably not. The size of the circle doesn’t change but if you think of it as a small circle, your biomechanics will follow and all of a sudden you are creating perfect circles! Try it – SMALL circles.
When biking, keep your chin parallel to the ground. Why? It improves breathing and keeps your head and neck in alignment.
Proper bike setup – Something I observe often is riders and spinners seats set too high. This causes their hips to rock down toward the ground as their foot reaches the bottom of the pedal stroke. It is both inefficient and puts undue stress on the knees. Proper setup will have your knees still slightly bent at the bottom of the pedal stroke and your hips will remain stationary.