I don't have a medical for it but it has to do with my lower spine. I've ridden a few standard Treks and found I was stretched just a bit too far forward. I'd last maybe 20 min. before I'd start to tighten up. Then when I gt off the bike, it was a painful hour or so before I could stand fully upright. With the Pilot, I never felt like I was reaching forward and I never felt any pain. I am wondering if the Cannondale Synapse would be a reasonable substitute?