Table 1 Questionnaire items related to the work environment

The environment of the workplace:

(1) Often work outdoors

(2) The floor of the workplace is unstable (e.g., slippery or rugged)

(3) Often exposed to significant trembling, vibration, or impact

(4) Often work in a noisy environment

(5) Often work in a narrow space

(6) Use fire during work

Working posture:

(1) Often work in a seated posture

(2) Often work in sitting posture

(3) Often work in a half-sitting posture

(4) Often work in a standing posture

(5) Often twist the waist during work

(6) Often bend forward at the waist to an extreme degree

(7) Often raise hands above shoulders or extend arms fully

(8) Sometimes work in a lying posture

The weight of carried loads (per person):

(1) Mainly 40 kg or more

(2) Mainly 20–40 kg

(3) Mainly 10–20 kg

(4) Do not handle heavy loads