Abstract
[Purpose] This study compared the isolated contraction ratios of the hip extensors, erector spinae muscles of the lumbar region, and thoracic muscles during different back extension exercises. [Subjects] Twelve males participated in this study. [Methods] The subjects performed various back extension exercises. The activities of the T7 erector spinae muscles, L3 erector spinae muscles, and the gluteus maximus were measured, and the isolation contraction ratios were calculated. [Results] The isolated contraction ratio of the T7 erector spinae muscles significantly increased during exercise 2. The isolated contraction ratio of the gluteus maximus increased by a significant degree during exercise 1 compared with the other exercises. [Conclusion] This study demonstrated that the back extension exercises 1 and 2 can be applied to selectively exercise the hip extensors, thoracic muscles, and muscles of the lumbar region.