Work Postural and Environmental Factors for Lower Extremity Pain and Malalignment in Rice Farmers

Abstract

In many Southeast Asian Countries, most tasks of the rice cultivation rely heavily on manual labor and require prolonged working in muddy terrain. Due to the lack of comprehensive ergonomic assessment and interventions, a series of studies were conducted to examine work postural and environmental factors contributing to lower extremity (LE) pain and malalignment in Thai rice farmers. This paper evaluates the collective results of our previous studies, which can be divided into two stages. The initial stage included a survey of pain perception and physical examination of LE alignment to specify the most problematic LE parts in a large group of 250 farmers, revealing that farmers generally perceived elevated hip pain. However, physical examination identified a high prevalence of foot pronation and knee valgus. A subsequent detailed analytical stage, conducted to identify factors of LE pain on a smaller group of 30 farmers, included two-stage ergonomic risk assessment and investigation of effects of muddy work terrain in different laboratory settings. The ergonomic assessment results indicated the planting process to pose the highest risk for LE injury, specifically leading to perception of knee pain induced by motion and posture factors, and foot pain induced by force exertion. Experiential results showed muddy ground to induce significantly higher force on knees and higher levels of knee and ankle muscle exertion. The findings suggest that further development of interventions should focus on reducing awkward posture and muscular exertion due to mud resistive force, particularly for knee and foot during the planting process.