Increased Stiffness Is Evidenced in the Deep But Not Superficial Lumbar Multifidus Muscle in Professional Athletes With Chronic Low Back Pain. - Zhou, Emma Feng Ming; Wong, Arnold Yu Lok; Lin, Guohui; Fang, Jianhui; Wen, Tao; Peng, Juhua; Fu, Siu Ngor (Archives of Physical Medicine & Rehabilitation, 2025)