Three-Dimensional Kinematic Comparison of Spoon and Chopstick Use During Ingestion

Background/Objectives: Human feeding behavior involves the use of various tools. However, the kinematic differences between commonly used utensils such as spoons and chopsticks remain insufficiently understood. The current study aimed to quantitatively characterize and compare the three-dimensional kinematics of spoon and chopstick use during ingestion. Methods: A total of 24 healthy adult men (mean age: 27.4 years) were instructed to ingest green soybeans one at a time while seated at a desk. Three-dimensional kinematic data of the eating tools were recorded, and movement trajectories were modeled using polynomial approximations. Movement characteristics, including trajectory patterns, spatial displacement, and duration, were analyzed using multilevel modeling. Results: Multilevel analysis identified statistically significant trajectory patterns, showing that chopsticks exhibited more curved and laterally deviated trajectories, being inserted from a more frontal direction and directed posteriorly and superiorly within the oral cavity, whereas spoons followed more linear paths. Chopstick use was associated with significantly greater spatial displacement across multiple axes compared with spoon use. Overall movement duration was significantly shorter during chopstick use, whereas insertion durations did not differ significantly between tools and withdrawal duration was slightly shorter with chopsticks. Conclusions: These findings demonstrate that the same behavioral goal—transporting food to the mouth—is accompanied by different tool-related kinematic patterns. The observed endpoint patterns may reflect utensil geometry and functional constraints; however, their relationship to underlying movement organization cannot be determined from tool-tip kinematics alone. The results provide a quantitative biomechanical characterization of tool-related feeding movements and may contribute to the evaluation of functional feeding movements.