When it was really bad for me, at first I could barely walk just around my appartment, then I slowly graduated to walking to the mailbox and going up the stairs (super slow). Then started exploring a little further, until I was able to slowly walk around the block or so. I'm almost a year into my PCS and can only tolerate 30-40 mins of slow walking.
But being able to get outside and do some walking always felt great. Sometimes it feels like a slow walk after dinner actually helps with my symptoms.