2.4. Study population
The study population consisted of Thai rubber tappers in Sawi
District, Chumporn Province who were employed in a rubber
plantation for at least one month and were between 15 and 60
years old. Participants who had any history of major back trauma
such as a motor vehicle accident, sports injury, fall from height,
potentially serious spinal condition including cancer, compression
fracture, spinal infection, ankylosing spondylitis, spinal stenosis,
herniated disc, cauda equina syndrome, drug abuse and mental
disorder were excluded.