I had disabling sciatica for a year and I thought a break from work would do me good; perhaps 3 months of exercise, no slouching over a computer, no deadlines, etc. would improve the situation. Nothing worked. In desperation, I consulted many, many specialists, even chiropractors, but nope, no change.
Alas, I had banked on _something_ changing in 3 months, so I had planned a walking holiday in Western Ireland (Dingle) before rejoining work. I wasn't prepared to cancel the tickets, so I went anyway. I took along a plywood board to help me sit angled on the seat to avoid having to sit at right angles!
Started the walk on The Dingle Way in a dubious frame of mind. I knew I was doing it only because I was too cheap to cancel tickets. Then magic happened. The place is so exquisitely beautiful that I walked 25 kms on the first day, even sharing a backpack with my wife. That evening, everything was hurting, but not in the usual places I had been conditioned to expect. The sciatica was GONE! I couldn't believe it, but it didn't recur the next morning. It has been 20 years now.
It is possible mine was a simple case that just required a structural realignment. But I had tried walking before, and many other strategies to improve posture etc. In hindsight, the only difference is that my brain in Ireland was fully engaged in the beauty of the place and people, and disengaged from the pain. Perhaps exercising my back without being focused on a cure is what worked.
Who knows? Perhaps this anecdote is of some value to your friend.
Thank you, Ireland!