Relationship Between Arm Swing Angles and Intervertebral Spinal Rotation Angles During Treadmill Walking.

Introduction Arm swing during walking plays an important role in reducing energy expenditure and enhancing motor control. Arm swing has been traditionally considered to occur due to passive factors associated with spinal rotational movements. However, the relationship between arm swing angles and rotational angles at each spinal level remains unclear. Therefore, this study aimed to investigate the relationship between arm swing angles and spinal rotation angles at each level. Methods A total of 21 young, healthy males were included in this study. Measurements were performed during steady-state walking on a treadmill (Split R, SENSTYLE Ltd., Kumamoto, Japan) at a controlled speed. The spine was divided into four levels using a three-dimensional motion analysis system (VICON MX-T, Vicon Motion Systems Ltd., Oxford, UK): upper thoracic (T1-T7), lower thoracic (T7-L1), upper lumbar (L1-L3), and lower lumbar (L3-S). The system calculated the horizontal plane rotation angles at these levels during one gait cycle and the sagittal plane rotation angles of the lateral epicondyles of the left and right upper arms as arm swing angles. Statistical analysis was performed to compare differences in arm swing angles between the left and right arms and in rotation angles between the spinal levels. Additionally, correlation analysis was performed to evaluate the relationship between arm swing angles and spinal rotation angles at each level. Results The left arm swing angle was significantly greater than the right arm swing angle. The rotation angle at the T1-T7 level was the lowest among all levels. Additionally, the analysis of the relationship between arm swing angles and spinal rotation angles revealed that the left arm swing angle was significantly positively correlated with the L3-S angle. Conclusions Although the lower lumbar vertebrae influence left arm swing during steady-state walking, arm swing is not entirely dependent on the rotational movement of the entire spine and may be influenced by multiple other factors.