Tehran University of Medical Sciences Iranian Journal of Public Health 2251-6085 49 10 2020 10 01 1894 1901 Ji-Hoon CHO Department of Sport and Leisure Studies, Shingyeong University, Hwaseong, Republic of Korea Ki-Hyuk LEE Department of Sport Culture, Dongguk University, Seoul, Republic of Korea Seung-Taek LIM Institute of Sport Science, Kangwon National University, Gangwon-do, Republic of Korea AND Nasaret International Hospital, Incheon, Republic of Korea AND Waseda Institute for Sport Sciences, Waseda University, Saitama, Japan 2020 02 04 2020 05 29 Background: The purpose of this study was to find the basic data of medical and exercise therapy by indexing lumbar extension muscle strength of low back pain (LBP) patients. Methods: In this cross-sectional study, 3078 chronic LBP participants from The J hospital, Seoul, Republic of Korea, from 2003 to 2010 were enrolled. Maximum muscle strength was measured at maximum flexion angle and maximum extension angle according to range of motion (ROM) results. For each isometric test, participants were seated and secured in the MEDX (medx lumbar extension machine, Ocala, FL, USA) machine. Results: The relative ROM (P=0.012) differed significantly among the aged groups in all participants. In addition, mean of strength (P<0.001), maximal of strength (P<0.001), mean of strength %BW (P<0.001) and maximal of strength %BW (P<0.001) are significant differences in all participants. The results of multiple regression analysis was the ‘model A’, maximal of strength for 32.1% of the variance in weigh, body mass index and range of motion. In addition, ‘model B’ was 30.4%, ‘model C’ was 28.8%, ‘model D’ was 28.5%, ‘model E’ was 21.7%, and ‘model F’ was 23.5% of the variance in weigh, body mass index and range of motion. Conclusion: We found the three predictor (weight, BMI, and ROM) variables accounted for 32.1% of the variance in maximal of strength %BW, the highest in < 29 yr groups. Our data indicate the basic data of medical and exercise therapy by indexing lumbar extension muscle strength of LBP patients. https://ijph.tums.ac.ir/index.php/ijph/article/view/19653 https://ijph.tums.ac.ir/index.php/ijph/article/download/19653/7005