Stretching “a lot” can certainly cause the nerve to become re-inflamed. The nerve is a membrane that has some damage to it due to the initial herniation. Healing takes some “quiet time” for the nerve. The nerve can be “moved” in a normal day to day fashion during this healing but significant stretch of the legs will stretch the nerve.
This does not mean that activity will inflame the nerve but heavier stretching and cardiovascular activity can.
Donald Corenman, MD, DC is a highly-regarded spine surgeon, considered an expert in the area of neck and back pain. Trained as both a Medical Doctor and Doctor of Chiropractic, Dr. Corenman earned academic appointments as Clinical Assistant Professor and Assistant Professor of Orthopaedic Surgery at the University of Colorado Health Sciences Center, and his research on spine surgery and rehabilitation has resulted in the publication of multiple peer-reviewed articles and two books.