Biomechanics of increased exposure to lumbar injury caused by cyclic loading: Part 1. Loss of reflexive muscular stabilization.

摘要: Study design The recording of electromyographic responses from the in vivo lumbar multifidus cat, obtained while cyclic loading was applied as occupational bending/lifting motion over time. Objectives To determine whether effectiveness stabilizing reflexive muscular activity diminishes during prolonged activity; recovery lost muscle by a 10-minute rest; and such diminished is caused fatigue, neurologic habituation, or desensitization mechanoreceptors spinal viscoelastic tissues resulting its laxity. Summary background data literature repeatedly confirms observation that functions expose workers to 10-fold increase episodes low back injury pain. biomechanical evidence indicates creep spine causes increased laxity intervertebral joints. impact on function muscles, which are major structures spine, not known. Methods Electromyography performed L1 L7 muscles passive 0.25 Hz L4-L5. Cyclic for 50 minutes, followed 10 minutes rest second 50-minute session. A third period also after preload reset 0.5 N offset effect Results Reflexive recorded all levels at initiation first loading. Activity electromyography quickly with each cycle 8 15% initial value. slower decrease evident throughout remaining period, settling 5% 10% level end minutes. provided 20% 25% activity, but within minute cycling. Offsetting resulted full restoration levels. Conclusions induced result desensitizes within, manifest dramatically allowing exposure instability injury, even before fatigue musculature sets in.