I've been going numb in the saddle a lot recently, which I find alarming, to say the least. I ride a Cannondale R 900 which was set up at the shop where I purchased the bike by an experienced tech who is about my size, 6'3" and a couple of pounds over 200. Recently I've been able to push myself on the road, thanks to cardiac ablation surgeries that seem to have fixed a problem I've had for the last ten years, atrial fibrillation. Now that I'm getting in better shape, my riding posture has improved. I ride down on the drops most of the time, and use the aero bars that were recently installed for a couple of miles at a time, traffic and terrain permitting. Since I've been riding lower, I've noticed frequent numbness, which while I've read is not uncommon, cannot be good. I'd like to avoid complicating any plumbing issues that are a natural consequence of the aging process; I'm 53, and hope to continue riding to the best of my ability for some years to come. Would someone explain what's happening, and what I might do to avoid it? Thanks!