Abstract
Background
Courier service workers transport diverse packages on delivery trolleys. The repetitive pushing and pulling tasks of manual delivery trolleys can increase the risk of work-related musculoskeletal disorders among courier workers.
Objective
A comparison of different trolley types, task types, and transport directions was conducted to determine the physical workload and ergonomic demands of pushing and pulling tasks during last-mile deliveries.
Methods
A within-subjects experiment was conducted with 23 professional male courier workers. Participants performed pushing and pulling tasks with three delivery trolleys: a hand truck, hand cart, and rolltainer. Trolley type, task type, and transport direction (straight and curved) were examined. Muscle activity was measured using electromyography (sEMG). Joint flexion angles were obtained from video recordings using the OpenPose Body-25 model. Lumbar compression and shear forces were estimated using the 3D Static Strength Prediction Program (3D SSPP).
Results
Pulling generally induced greater activation of upper-limb muscles and greater flexion of the lower arms and neck than pushing, whereas pushing resulted in greater trunk flexion. Among the trolley types, the hand cart produced the highest muscle activity and the greatest lumbar compression and shear force. Hand trucks imposed the lowest biomechanical demands. Pulling a hand cart generated the greatest load on the lower back. Speeds of transport ranged from 0.66 to 1.15 m/s, with pushing and straight-line movements achieving significantly faster speeds than pulling and curved movements. Last-mile delivery caused the most subjective discomfort in the arms, followed by the lumbar region, while shoulders caused the least discomfort.
Conclusion
The findings indicate that trolley type and handling method substantially influence courier delivery workload and biomechanical demands. In routine delivery tasks involving moderate loads, hand trucks may be an ergonomically beneficial option. The findings of this study provide practical evidence for improving trolley selection, work methods, and injury prevention strategies in the courier industry.