You do also have to concentrate on core stability, relaxed but solidly placed. imagine the gut area is made of stone, or lead and it is the centre of you and the bike as you pedal. upper body and arms should be relaxed but not floppy. It also helps if your bar height and reach is set up correctly to distribute your weight and balance optimally. This is why many novices find it easier to spin whilst sitting upright, as the weight is taken from the arms/shoulders and placed over the saddle, keeping the core stable, unfortunately this become counter productive once you get into higher cadences, varying between people but maybe around 190-200RPM. This isn't to say people can't still pedal smoothly at 200RPM whilst sitting right back, but these are all considerations.
You do also have to concentrate on core stability, relaxed but solidly placed. imagine the gut area is made of stone, or lead and it is the centre of you and the bike as you pedal. upper body and arms should be relaxed but not floppy. It also helps if your bar height and reach is set up correctly to distribute your weight and balance optimally. This is why many novices find it easier to spin whilst sitting upright, as the weight is taken from the arms/shoulders and placed over the saddle, keeping the core stable, unfortunately this become counter productive once you get into higher cadences, varying between people but maybe around 190-200RPM. This isn't to say people can't still pedal smoothly at 200RPM whilst sitting right back, but these are all considerations.