上肢肌肉骨骼傷害之危害因素包括工作姿勢不良、過度施力、高重複 性及工作與休息安排等因素,對於上肢高重複性工作與休息時間安排之相 關探討仍為少數。 本研究利用生理訊號量測系統、荷重計及心率監視器,收集12 位男性 受測者從事重複性作業時,其右手上肢肌群肌電訊號(Electromyography, EMG)、荷重及心搏率等資料,作業時間為9 分鐘。實驗因子包括4 種不 同休息時間(作業時間的0.25、0.5、1、1.5 倍)及2 種不同搬移重量(1 及2 公斤)。利用實驗室自行開發的Viewlog 軟體,計算各肌群EMG 之恢 復%MVC,以探討上肢肌群之肌力恢復情況。 結果顯示,肱二頭肌、中三角肌及前三角肌在休息時間為作業時間的 0.25 倍時,其肌肉疲勞之恢復與其他3 種休息時間具顯著性差異,於恢復 %MVC 中在休息時間為作業時間的0.5 倍時,恢復程度超過至90%以上; 肱三頭肌在休息時間為作業時間的0.25、0.5、及1 倍時與休息時間為作業 時間的1、1.5 倍有顯著差異。因此,建議搬移物重1 公斤及高重複性作業 時,休息時間建議可以設定為作業時間的0.5 倍,恢復程度在87.3%至98.6% 之間;若工作/休息時間安排成更短而頻繁之設計時,則建議休息時間能設 定為作業時間的0.25 倍,其恢復能力可達83.9%以上。
Four main ergonomics factors to affect the upper limb musculoskeletal disorders are: awkward postures, overexertion, repetition and work/rest. However, few literatures have been emphasized on the work and rest time arrangement for upper limb repetitive tasks. An experiment was conducted to collect electromyographic data (EMG), force and heart rate when a simulated repetitive task was performed in the laboratory. Twelve young male subjects were recruited. Eight experimental factors were included:4 different rest time periods (0.25, 0.5, 1, and 1.5 times of work time of 9 min) and 2 different object loads (1 and 2 kg), in this study. The Viewlog software developed was used to calculate %MVC (maximum voluntary contraction, MVC) from electromyographic signals of tested muscles to explore the upper limb muscle fatigue recovery. The EMG results showed that the rest time period change might significantly affect the tested muscles. The EMG results, on rest time period of 0.25 times work time, obtained from biceps brachii, middle deltoid, and anterior deltoid, had the significantly different muscle fatigue recovery (p<0.05) when compared with the other three rest time periods (the recovery more than 90%). The EMG results measured from triceps brachii on the rest time period of 1.5 times work time showed significantly different (p<0.05) when compared with the other rest time periods. It was recommended rest time should be taken at 0.5 times of the working time, and the recovery might reach between 87.3% and 98.6%.