A 37-year-old architect who has run with a club four mornings a week for six years has withdrawn from a half marathon she had already paid for and swapped her runs for swimming. She has also pulled out of a hut-to-hut hiking trip she had been planning for a year, because she could not face several days of carrying a loaded pack. It has been building gradually for about five months. Her training partner made the appointment after watching her stop and walk twice on their last Sunday run. She looks fit and entirely well, walks in without a limp, and is brisk and practical: she wants a plan, not reassurance.