重體力工作之評估研究──以鏟沙與敲擊作業為例

Evaluation of Heavy Physical Works-- Hammering and Sand-Shoveling

機械化已經大大的降低操作者作業時身體成本的付出，但在許多行業裡，仍有多項作業屬於重度工作。然而有關重體力工作之定義或是相關規範，國際間或學術上皆有所差異，但多數以勞工作業時的能量支出作為界定標準。雖然能量支出是衡量身體工作負荷的重要指標，但對於偶發性或局部性的工作而言，純粹採用作業型態或能量消耗的觀點作為界定依據似有不足之處。有鑑於此，本研究除收集工作分類界定標準外，並針對 6 位受試者實際模擬我國法定重體力作業（鏟沙與敲擊作業），收集其氧攝取量、心搏率、肌電訊號以及主觀評比等生理與主觀資料。研究結果顯示，鏟沙與敲擊作業兩項法定之重體力作業，會因作業型態的不同，工作時之能量消耗具有差異。在鏟沙作業中，平均的攝氧量為每分鐘 1.2 公升（6 kcal/min），心搏率為每分鐘 140 跳，鏟沙作業的攝氧量百分比為 59.0％。在敲擊作業中，平均的攝氧量為每分鐘 0.9 公升（4.5 kcal/min），心搏率為每分鐘 132 跳，敲擊作業的平均攝氧量百分比為 43％。以 AIHA 能量消耗標準來看，鏟沙作業每分鐘平均消耗6 kcal，是屬於重度作業；然而敲擊作業每分鐘平均消耗4.5 kcal，是屬於中度工作。局部肌肉疲勞的部分，敲擊時橈側屈腕肌、尺側屈腕肌與肱二頭肌的 NEMG% 大於鏟沙作業，其差異乃是因作業姿勢的不同（敲擊著重在手臂局部施力）所致。而在下背直肌 NEMG% 很明顯的可以看出，鏟沙作業大於敲擊作業，原因在於鏟沙必須將軀幹大幅度前彎（鏟的動作），直背後將沙投出，導致下背直肌 NEMG% 大於敲擊作業。實驗結果亦發現，受試者進行敲擊作業時會因為局部肌肉疲勞而放棄作業。

Although the cost of labor has been reduced through automation, many heavy manual tasks still exist in various industries. In most writing, the term“ heavy work” is defined by oxygen consumption during work. Oxygen consumption is well related to the load of work for whole-body exertion, but it does not seem to fit very well for static or local muscle exertion. Therefore, this study evaluated hammering and sand-shoveling tasks and collected data on oxygen consumption, heart beat rate, and muscle EMG. The results show that oxygen consumption varied for different activities. In sandshoveling, the average oxygen consumption was 1.2 l/min, about 59% of maximal VO2, and the average heart rate was 140 beats/ min. In hammering, the average oxygen consumption was 0.9 l/min, about 43% of maximal VO2, and the average heart rate was 132 beats/min. According to AIHA standards, sandshoveling can be rated as heavy work an hammering as medium-heavy work. The lower arm muscle EMGs for hammering were greater than those for shoveling, but the lower back muscle EMG was greater for sandshoveling. The subjects gave up hammering not because of the heavy load of oxygen consumption, but because of the heavy load on local muscles.