Sorry to read about your disc problems.Sounds like you've gotten results with the P.T. and that in itself is a good thing.The herniation most typically is the center,"nucleus populsis", that has a gelatenous composition has left the confines at the center of the disc and migrated through tears in the inner fiboruos rings.This creates the bludging that if protruding back and to the side effects the major nerve root at that level.The nucleus does sometimes retract and the torn rings can fill with scar tissue.This would be enhanced by not loading up the disc while any healing is taking place.Should say excessive loading.Especially in rotation which loads the outer rings.You can see the disc acting in a hydraulic manner.Since the disc is hydrophyllic, there's a transfer of fluid through the endplates of the vertebra above and below.Vertical loads push the N.P. outward and push the annular rings making them taut. Sitting loads the disc 6 times more than standing so sitting long periods typically increases symptoms of nerve root pressure. To me, in a lot of cases but not all,walking helps the healing process.This is why-Walking uses all the low back structures as they were intended to work and take loads.This simple normal movement gets everything working together ie; spine,pelvis,discs,ligaments,joint capsules,tendons,and muscles.Short walks on level ground,good footwear, with no increase in symptoms.Slowly building the walking time up without symptoms.I would probably tell someone to ice the low back at the spine for 15 minutes after walking.Also would advise someone to stop walking if symptoms reoccur.It helped in my case for what it's worth.No hurry just building up slowly