Having most ny vertebrae fused, I lost running ten years ago. I concentrate on walking, but lost that to gait disturbance. My cycling went by the wayside due to balance issues. I even tried using my hands to 'pedal' my exercise bike from the front.Not a real option. My option for aerobic exercise was lap swimming. Not my favorite exercise, having nearly drowning twice, but I got better at it after several years. Now I can do a mile in the locale aquatic center, year around. Since my legs were worthless in the pool, they dropped and impeded swimming. My physical therapist recommended a float device between my legs. What a relief! Keep on plugging!