well in AS , one certainly has to keep themselves physically fit (low body weight and High Muscle Strength) and keep moving the body parts.
If not able to walk is only difficulty then probably there is a compression of nerves which supply (lumbar region) lower extremity. If there is also a difficulty in moving Upper extremity then the compression is from NECK (cervical Region) and carefully therapy mobilization and strengthening along with traction would be required.
THE THerapy should that would be done will include releasing the compression (traction), + Muscle Release, + Stretching, +strengthening of mucle group,
Next Steps
Check with a PROFESSIONAL AND ONLY QUALIFIED PHYSIOTHERAPIST SPECIALISED IN NEUROLOGICAL or ORTHOPAEDIC stream so that he knows what exactly has to be done . and does it properly.
Health Tips
Please DONT RUSH THE PACE OF TREATMENT , IT WILL BE SLOW BUT STEADY, and EXPENSIVE (because of Longer Duration) but results are pretty good. STAY HEALTHY