The Effect of Grip Strength on Physical Workload in Manual Material Handling Tasks

Objective: The purpose of this research was to analyze the effect of grip strength on subjective physical workload according to the weight of objects and working posture in manual material handling tasks.<br/>Background: Studies related to the prevention of musculoskeletal diseases in Korea were concentrated on the analysis of the correlation between weight, force, and muscle. In most work sites, many tasks involve movements such as gripping objects, applying force, or using hand tools. However, studies investigating the relationship between worker's grip strength and their physical workload during such movements were insufficient.<br/>Method: 24 participants who predominantly used their right hand during work were selected. The grip strength of the subjects was measured. Subsequently, subjective physical workload was assessed using Borg's CR-10 Scale in a randomized experimental order. ANOVA was performed to analyze the effect of the grip strength on physical workload<br/>Results: ANOVA showed that both the weight of objects and the posture had statistically significant effect on subjective physical workload. The weight of objects statistically affected on Borg's CR-10 Scale values in both posture A (posture using the front arm) and B (posture with the arms extended to the maximum). However, grip strength showed a significant effect on subjective physical workload only in posture B, which required higher physical demand, while no significant effect was observed in posture A.<br/>Conclusion: Grip strength was associated with an increased subjective physical workload only under high-load condition during manual material handling tasks. In contrast, under lower workload conditions, grip strength dose not exert a significant influence.<br/>Application: The results of these studies were thought to contribute to the prevention of musculoskeletal disorders for workers in actual industrial sites who hold objects in their hands or frequently use hand tools, and can be used as basic data for future research related to grip strength.