inadequate time for relaxation. Most of them had a low level of
social support but still lived in supportive families. Otherwise, there
was no conflict with co-workers or the employers during the period
of work. During a period of depressed rubber prices, which were on
average 50 baht/kg at the time of this study, most of the participants
had an inadequate income but they were still satisfied with
their jobs (Table 2).
At the time of this study most of the participants were tapping
rubber trees at a level below their waist for durations of 6e12
months. The average working time at night was 6 h with an average
number of tapped trees at nearly 500 trees per person per day. The
physical ergonomic characteristics of the tapping task included
a high frequency of repetitive postures with weight lifting, bending
and twisting of the trunk. This task also had a prolonged period of
walking and standing (