Relationship between one-handed push force and subjective rating of force exertion

Abstract

BACKGROUND: Pushing is a typical workplace activity that may result in musculoskeletal disorders (MSDs). A convenient method of assessing the risk of MSDs is to determine the association between the force applied and the subjective rating of force exertion. OBJECTIVES: This study aimed to determine the relationship between the subjective rating of force exertion and the force applied to both a fixed and a movable handle. It also aimed to confirm that the participants could apply a higher one-handed push force at shoulder height than at elbow height. METHODS: A one-handed pushing experiment was conducted. In the push-to-scale session, the participants pushed a handle fixed on a rig on four levels on the CR-10 scale. The push force was measured. In the force-rating session, the participants rated their force exertions when pushing a movable handle with metal blocks suspended on the two sides. The subjective ratings on the CR-10 were recorded. RESULTS: The one-handed push force at shoulder height was significantly higher than that at elbow height. More effort was needed to push on a movable handle than a fixed one. Two regression models were established to describe the relationship between the push force and the subjective ratings of pushing for each of the fixed and movable handles, respectively. The correlation coefficient results showed that these models are adequate to describe the relationship between the one-handed push force and the ratings of the CR-10 scale. CONCLUSION: Participants applied a higher one-handed push force at shoulder height than at elbow height was confirmed. Participants needed more efforts to push the movable handle under the same CR-10 level than the fixed handle. The predictive models developed in this study may be used to estimate the push force for one-handed pushing tasks when assessing the risk of MSDs.