Hi, On good days, I can walk 30 mn twice a day. That makes for me 3600 steps each time.BUT... Those are steps in my little garden, or park, on the grass without people around, no noise or any disturbances from the city life. This day, I woke up with good parameters - thought it was a good day- and I tried to walk on the pavement of the path outside of my building. 8h30 in the morning, any one except my physiotherapist with me (in case of a problem). The path begins with some gradient, so I know that I have to climb it on my return. I made about 80-100 meters before to go back, and after sveral steps, I began to experiment bad symptoms -always the same . It begins with contraction in my thighs (quadriceps), then I begin to feel spacey and struggle for each steps with the fear that I won't make it. It is less than 60 steps to the top, but real struggle. Sympathetic nervous system on alert, all the alarms are "ringing" and then I have to stop everything for a while. Classic PEM, but after 120 steps in total, far from the 3600 that I can on a regurlar basis on the grass (even with some gradient). What is the logic here ??? And this is always the same ! I can't reach any autonomy outside the house without my wheelchair. I have been sick with ME/CFS 20 years, and this phenomenon has been recurrent for more than 10 years now. As if, walking on the pavement was reminding of all the bad past evenements when I collapsed on the ground and couldn't stand up then for hours and days. Everytime (except once) it happened on street walking, standing in buses or shops, NEVER IN NATURE WITH CALM. STEPS in crowdy/city environnements are not equal to steps in the nature/wilderness OK I understand. I can understand the over-stimulation that the brain is experimenting. But 3600 steps against 60 steps I don't understand this gap ! As if there was some PTSD reactivated by the nature of the ground/environnement (all the past collapses on pavement/floors crowdy environnements) within just a few steps ! Do you experiment something like this ?