Very good point dogmama. If you want a fluid stroke, using as many different muscles as possible you must be clipped in. Toe clips are truly inferior on this point, but certainly better than nothing at all. I love one legged drills. I always unclip my other leg and then you really learn how much stronger one leg is than the other. Plus you really learn where you are making mistakes on your circular motion. You really have to complete the circle to keep up your cadence. No quad pumping!