坐姿全身振動暴露頻率與姿勢對腰背肌群之影響探討

工作場所各種不同型態工作人員長期暴露在全身振動中，全身振動暴露可能會造成前庭系統受損、生殖系統影響、與下背痛的產生，嚴重時導致椎間盤突出等傷病。在醫療上，全身振動被使用在復健中風患者或是中樞神經受損病患的物理治療；也有不少的運動訓練將全身振動作為肌肉訓練的方式，透過振動的刺激在復健上或是運動訓練上，促使牽張反射(Tonic Vibration Reflex, TVR )增進肌力、刺激神經肌肉(Neuromuscular)有更好的效益。本研究召募20名成人男性作為受測者，針對腰背肌群量測坐姿振動後，肌肉活化的程度以及身體平衡的影響。研究中使用生理肌電訊號(Electromyography, EMG)、振動平台、平衡評估系統，探討振動頻率、坐姿、與平衡的影響，並透過頻譜分析評估肌肉疲勞狀態。 研究結果顯示高頻(40Hz)振動對直立坐姿、扭轉坐姿有顯著影響，並在腰部肌肉(腹直肌、腹外斜肌)活化的程度較高。在直立坐姿經由振動後平衡能力受影響最大，且不論是在高、低頻振動皆有影響；但在肌肉疲勞指標及頻譜-振幅合併分析(Joint Analysis of EMG Spectrum and Amplitude ，JASA)顯示肌肉呈現疲勞人數並不多。由本研究結果增加了解振動頻率與坐姿，對人體腰背部肌肉與平衡能力的影響。

Workers from varying occupations with long-term exposure to vibrations to their entire bodies may result in damage to the vestibular system, the reproductive system, lower back pain, and in severe cases, herniated intervertebral discs. In the medical field, whole body vibration is used for the rehabilitation of stroke patients or physical therapy for patients suffering from damage to the central nervous system; many athletes also use whole body vibrations as a method to train muscles by utilizing the stimulation of vibrations in therapy or training to induce tonic vibration reflex (TVR) and increase muscle strength or cause neuromuscular stimuli for better benefits. This study recruited 20 adult males as subjects to measure the impact of exposing the lumbar-back muscles to vibrations in a seated posture and how muscle activation and balance are affected. The study utilized electromyography (EMG), vibration platforms, and balance evaluation systems to explore the impact of vibration frequency, sitting posture, and balance; frequency analysis was used to analyse the conditions of muscle fatigue. Study results concluded that high frequency vibrations (40Hz) had a significant effect on upright and torsion posture and a higher degree of activation in lumbar muscles (rectus abdominis and ventral oblique). Balance ability was most heavily affected after vibrations in the upright posture, regardless of whether vibrations were set at high or low frequencies. However, in the muscle fatigue index and spectrum – amplitude analysis (analysis of EMG spectrum and amplitude, JASA) results showed that few test subjects suffered from muscle fatigue. The results of this study may increase our understanding of the effects of vibration frequency and sitting posture on the lumbar-back muscles and balance.