This study investigated the effect of static or dynamic back extensors endurance exercise in combination with McKenzie Protocol (MP) in patients with Long-term Mechanical Low-Back Pain (LMLBP). This randomized controlled trial involved 84 patients, who were assigned into MP Group (MPG), MP plus Static Back Extensors Endurance (SBEE) Exercise Group (MPSBEEG), or MP plus Dynamic Back Extensors' Endurance (DBEE) Exercise Group (MPDBEEG). Twenty-five, 22, and 20 participants in MPG, MPSBEEG, and MPDBEEG, respectively, completed the thrice weekly eight-week study (drop-out rate = 20.2%) and outcomes were measured in terms of SBEE, DBEE, and Back Muscles Fatigue (BMF) at the 4th and 8th week, respectively. There were significant differences in groups mean change scores on