Abstract
BACKGROUND: Efficient methods to reduce erector spinae stiffness are important for solving lumbar spine problems, however, the trunk training positions effective for reducing erector spinae stiffness are unclear. Furthermore, it unclear whether whole-body vibration and trunk training are synergistic. Therefore, this study aimed to clarify the differences in the immediate effects on reducing erector spinae stiffness among three types of training: simple spinal flexion training, spinal neutral position training, and spinal flexion training combined with whole-body vibration. METHODS: This single-blind randomized controlled trial included 36 healthy university students who were assigned to either the spinal neutral position training group, spinal flexion training group, or whole-body vibration (vibration conditions: 35 Hz, 4 mm) + spinal flexion training group. Training consisted of only one session of the assigned exercise in each group (20 s × 8 sets, rest 15 s). The outcomes measured were erector spinae stiffness, tenderness threshold of the erector spinae, lumbar proprioception, and maximum lumbar forward bending angle. All statistical analyses were performed using a split-plot design analysis of variance. RESULTS: There were no significant group × period interactions for erector spinae stiffness; however, a significant main effect of time was observed (p < 0.01). Comparison of pre- and post-intervention stiffness indicated no significant differences in the spinal flexion training group. In contrast, both the spinal neutral position (p < 0.01, pre-intervention: 49.0 [10.6], post-intervention: 47.1 [6.4]) and whole-body vibration + spinal flexion training groups (p = 0.02, pre-intervention: 49.8 [12.6], post-intervention: 47.9 [9.4]) showed significantly less stiffness post-intervention compared to pre-intervention. CONCLUSIONS: Trunk training performed in the spinal neutral position or spinal flexion position combined with whole-body vibration reduces erector spinae stiffness more effectively than simple spinal flexion training. TRIAL REGISTRATION: This study was registered in the Japan Registry of Clinical Trials as a clinical trial (ID: jRCT1042240153; registration date: 20/12/2024).