Repetitive trunk flexion can damage spinal tissues, however its association with low back pain in the workplace may be confounded by factors related to pain sensitivity. Muscle fatigue, exercise-induced hypoalgesia, and creep-induced neuromuscular changes following repetitive trunk flexion may all affect this assumed exposure-pain relationship. This study’s purpose was to determine how mechanical pain sensitivity in the low back is affected by a repetitive trunk flexion exposure and identify factors associated with changes in low back pain sensitivity. Pressure pain thresholds, perceptions of sub-threshold stimuli, and muscle fatigue in the trunk and tibia, as well as lumbar spine creep were tracked in 37 young healthy adults before and up to 40 min after a 10-min repetitive trunk flexion exposure. Pressure pain thresholds (p = 0.033), but not perceptions of sub-threshold stimuli (p > 0.102) were associated with approximately a 12.5% reduction in pain sensitivity 10 min after completing the exposure, while creep and local muscle fatigue effects were only observed immediately following the exposure. Creep and fatigue interactions and the corresponding tibial measure co-varied with individual low back pressure pain thresholds. The net hypoalgesic effects of repetitive trunk flexion have the potential to partially mask possibly injurious loads, which could contribute to the severity or incidence of lower back injuries related to these exposures.

反复的躯干屈曲会损伤脊柱组织，但是其与工作场所中的下背痛的关联可能会与疼痛敏感性相关的因素混淆。反复的躯干屈曲后，肌肉疲劳，运动引起的痛觉过敏和蠕动引起的神经肌肉变化都可能影响这种假定的暴露疼痛关系。这项研究的目的是确定反复的躯干屈曲暴露对下背部机械疼痛敏感性的影响，并确定与下背部疼痛敏感性变化有关的因素。在37名年轻的健康成年人中，在重复10分钟重复性躯干屈曲之前和之后的40分钟内，追踪压力痛阈值，对躯干和胫骨的亚阈值刺激和肌肉疲劳以及腰椎蠕动的追踪。压力疼痛阈值（p = 0.033），但在暴露完成后10分钟，对低于阈值的刺激的感觉（p> 0.102）并不会使疼痛敏感性降低约12.5％，而蠕变和局部肌肉疲劳效应仅在暴露后立即观察到。蠕变和疲劳相互作用以及相应的胫骨测量值与各个低背压痛阈值共同变化。躯干反复屈曲的净镇痛作用有可能部分掩盖可能有害的负荷，这可能会导致与这些暴露相关的下背部受伤的严重性或发生率。而蠕变和局部肌肉疲劳效应仅在接触后立即观察到。蠕变和疲劳相互作用以及相应的胫骨测量值与各个低背压痛阈值共同变化。躯干反复屈曲的净镇痛作用有可能部分掩盖可能有害的负荷，这可能会导致与这些暴露相关的下背部受伤的严重性或发生率。而蠕变和局部肌肉疲劳效应仅在接触后立即观察到。蠕变和疲劳相互作用以及相应的胫骨测量值与各个低背压痛阈值共同变化。躯干反复屈曲的净镇痛作用有可能部分掩盖可能有害的负荷，这可能会导致与这些暴露相关的下背部受伤的严重性或发生率。