With EDS, strength can take the place of lax ligaments. The only problem with muscle tone is that fatigue can set in which is the limiting factor in EDS. I would not engage in activities that would stretch the spine like yoga but work on core and strength.
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.