Purpose <p>No studies have elucidated the dynamic spinal balance in patients with dropped head syndrome (DHS) categorized by global spinal alignment. We investigated the differences in dynamic spinal balance and corresponding muscle activity during prolonged walking in patients with DHS based on their global spinal alignment.</p> Methods <p>Three-dimensional gait analysis combined with electromyography was conducted to evaluate kinematic spinal parameters during walking, including the sagittal vertical axis (SVA) in the cervical (C-SVA), thoracic (T-SVA), and lumbar (L-SVA) regions, along with the muscle activity. Patients were divided into two groups based on C7 SVA from standing whole spine radiographs: SVA + and SVA–. Parameter changes were compared between the first and final laps of prolonged walking in each group.</p> Results <p>Twenty-eight patients were included (11 in the SVA + group and 17 in the SVA– group). In the SVA + group, prolonged walking caused a significant increase in T-SVA and L-SVA (<i>P</i> = 0.002, 0.014), with no compensatory increase in paraspinal muscle activity. In the SVA– group, C-SVA and T-SVA increased significantly (<i>P</i> = 0.002), with a decrease in cervical paraspinal muscle activity (<i>P</i> = 0.009).</p> Conclusion <p>Three-dimensional gait analysis with electromyography highlighted the distinct pathophysiological mechanisms in patients with DHS, as determined by their global spinal alignment. In the SVA + group, gait-induced thoracolumbar imbalance increased without compensatory activation of the lumbar paraspinal muscle. Conversely, in the SVA– group, gait-induced cervicothoracic imbalance increased without compensatory activation in cervical paraspinal muscle activity. These findings suggest that although DHS presents with similar symptoms, it may involve different underlying pathophysiologies depending on the global spinal alignment.</p>