Investigation of diaphragmatic and deep abdominal muscle function in patients with ankylosing spondylitis and its relationship with clinical parameters: An ultrasound-based study - Ugur Verep; Tuba Demirci Yildirim; Ozkan Urak; Fatos Onen; Ismail Sari; Seher Ozyurek (Journal of Back and Musculoskeletal Rehabilitation, 2026)