Evaluating Ergonomic Risks in Manual Lychee Harvesting Using PATH and Hierarchical Task Analysis: An Observational Cross-Sectional Study.

Musculoskeletal disorders (MSDs) are prevalent among agricultural workers, particularly during harvesting activities involving awkward postures and heavy manual handling. Despite Thailand's significant role in global lychee production, ergonomic risks in lychee harvesting remain under-investigated, even though exposure is evident. This cross-sectional observational study was conducted during the 2022 lychee harvest season across eight orchards in Phayao Province, Thailand. A total of 104 male harvesters were systematically video-recorded during full-task execution. Hierarchical Task Analysis (HTA) was used to segment workflows into goal-directed sub-tasks, and ergonomic exposures were assessed using the Posture, Activity, Tools, and Handling (PATH) method, with postures coded as neutral or non-neutral using a structured checklist. The harvesters were predominantly older working-age adults (mean age 53.5 years) who worked long hours (7.65 hours/day), often carrying 9.5 kg baskets unilaterally on one shoulder. Postural analysis revealed frequent ergonomic risks: 59% of neck postures and 58% of trunk postures were non-neutral, including 15% with severe forward flexion and 24% involving lateral bending or twisting. Arm elevation above shoulder height was common during climbing and fruit detachment. Spatial layout imposed long travel distances (over 30 meters), contributing to cumulative fatigue. Ladder height, tool design, and task repetition further exacerbated biomechanical strain. Lychee harvesting imposes significant ergonomic risks due to non-neutral postures, load asymmetry, and task repetition. Evidence supports the urgent implementation of ergonomic interventions, including bilateral-carry basket redesign, improved ladder safety, and participatory workflow reorganization to reduce WMSD risks in seasonal fruit agriculture.