Just diagnosed with same problem. X-ray today confirmed stress fracture of 3rd metatarsal, been unable to run for 2.5 weeks now although cycling 30-50 miles a day 3 times a week doesn't cause any pain (running would be agony). I thought training for April's FLM (1st marathon)was going so well, anyone got any advice as to how long this takes to heal before one can sensibly start running again and any tips as to helping it heal properly. rgds.