A study on trunk muscle activation patterns according to tilt angle during whole body tilts

Background: Lower back pain has a lifetime prevalence of 80% for people in a modern society, and in recent years, spinal stabilization movement has been highlighted as a method to treat lower back pain and an unbalanced position. Objective: The objectives of this study were to assess the trunk muscle activities in accordance with the tilt angles (10°, 20°, 30°, 40°) during trunk tilt exercises with a 3D dynamic exercise device. Methods: Active tilt mode (a self-generated active movement in the angle and direction steered by the user) was used in this study. The rotation capability enabled the investigation of the anterior (A), anterior right (AR), right (R), posterior right (PR), posterior (P), posterior left (PL), left (L), and anterior left (AL) tilt directions. EMG signals of the trunk (3 global muscles: rectus abdominis, RA, external obliques, EO, latissimus dorsi, LD, and 1 local muscle: multifidus, MF) muscles were obtained. Results: The MF muscle activity was higher while the anterior tilt was maintained, and the abdominal muscle activity was higher while the posterior tilt was maintained. Also, as the tilt angle increased, the activity of the muscles opposite the tilt direction increased. Conclusions: The results indicate that to maintain equilibrium through posture stabilization during whole body tilting, the human body maintains a proper interaction among the body segments as well as between the body and the execution environment. Moreover, stability is maintained through the co-contraction of antagonistic and agonistic muscles. In future studies, it will be important to conduct research on improving imbalance in the trunk muscles.