Healthiest posture
Assuming zero preexisting back problems, what would be the healthiest cycling posture to maximize back AND knee health in the long-run? Is upright posture of European / classic roadster bike better than bent over road bike posture? Why? I'm guessing that an upright posture allows for better spine neutrality, but I'm not sure. Are there any legitimate studies on the subject (as opposed to uneducated opinions)?
Thanks!