Maintaining a flat back is necessary in many sporting activities. For example, in doing squats, a rounded back will promote a tendency toward herniated discs because weight on the discs is not evenly distributed. Similarly, in cycling, it is recommended by sport physiologists that the back be straight and that the forward lean be accomplished by bending at the hips. The best example of poor posture on the bike is Lance Armstrong who has a pronounced arch in his back. http://www.doobybrain.com/2009/07/24...a-trek-madone/ As a man who also has back problems I'm always careful with my back. Maintaining a flat back keeps me pain free on the bike. It may be that this approach will work for you.