This study investigated the physical stresses in tractor logging operations using skidding road. As heart rate was considered a very useful index to evaluate physical stress, heart rate of a tractor operator during work was measured in this study. Of the work elements, prehauling (log gathering activities) was found to be higher intensity work, as it increased heart rate by as much as 60-70%. But energy consumption of the operator in this operation was moderate, because the rate of working time of those elements was low. Additionally, it was found that the operator's mental stress while driving on the skidding road was relatively high and the rate of working time of driving was high. Therefore, it was considered that reducing mental stress or strain would be necessary in this logging operation.

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In the investigations at actual tractor skidding sites, it was recognized that there was an increase in the operator's heart rate during off-road driving relative to on-road driving. There was no difference in heart rate if off-road driving was under good ground conditions at a slow speed. But in a simulated test, heart rate during off-road driving was higher than that during on-road driving when driving speed was the same. Therefore, it is clear that driving speed during off-road driving is a significant factor affecting the operator's physiological burden. Consequently, the tractor logging operation using skidding road is better in decreasing the operator's physiological load, keeping safer working conditions and improving productivity.

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