チェンソー運搬者の生理的負担について

Abstract

森林作業, とりわけ伐木造材作業において大きい部分を占め、しかも作業負担の著しいチェンソー運搬作業を取りあげ, 運搬時の作業者の負担がどの程度なのか, また主たる影響因子は何であるかについて, チェンソー重量と作業負担の関係を中心にして検討した。そのために, 無線テレメーターを用いて作業中の作業者の心電図を連続して測定し, それら心電図から作業負担の指標としての心拍数を算出した。その結果, 作業者の心拍数水準から考えて, チェンソー重量は7kg以下であることが好ましく, 少くとも11kg以下でありたいこと, また運搬作業に影響を与える主たる因子は, 路面の状態, 運搬速度, 運搬方法等であることが明らかになった。

The carriage of the chain-saw occupies considerable weight in the felling and bucking operations, and the operation load of this is remarkable. Accordingly, in this paper we have dealt with this carrying operation, and investigated the level of the operation load and the major factors influencing the operation, in order to look for clues as to the possible reduction of the operation load of chain-saw operaters. Using a wireless telemeter, the electrocardiograms of carriers were recorded throughout the operation. From these electrocardiograms, heart-rate was calculated as the index of the operation load for each operation (for further details, see Literature 1), 2)). A summary of the results is shown below. 1) If possible, it is desirable to keep the weight of the chain-saw under 7 kg and, at least, under about 11 kg judging by the levels of heart-rate of the carriers (see Fig. 1). 2) As the results of the analysis of variance, the major factors influencing the operation were, in order, "Condition of road", "Speed of carriage" and "Method of carriage" (see Table 6). "Weight of chain-saw" generally had little influence compared with these three factors, but had great influence on carriage uphill (see Table 7). "Difference in age and working experience of workers" had little influence on heart-rate, but had remarkable influence on the standard deviation and the coefficient of variation of heart-rate (see Fig. 13 and Fig. 2). i) Average heart-rate increased by about 20% when carrying uphill (average inclination 7.9%) as compared with level ground, though there is little difference between downhill (average inclination 7.9%) and level ground (see Fig. 6 and Table 10). ii) Average heart-rate increased by about 17% when carrying at a fast pace (average speed 100 m/min.) as compared with an ordinary pace (82 m/min.), but decreased by only about 1.5% at a slow pace (65 m/min.) as compared with an ordinary pace (see Fig. 9). iii) Average heart-rate decreased by about 8.7% when carrying on the shoulder and about 12% with a SHOIKO, as compared with hand carriage. Therefore, when carrying a chain-saw over long distance such aids as the SHOIKO would be useful (see Fig. 10). iv) The range of heart-rate under 48 different types of conditions was 84-124 beats/min. and 98 beats/min. on average.