The influence of rice plow handle design and whole-body posture on grip force and upper-extremity muscle activation

Abstract

A previous job screening study revealed ergonomics risk factors in rice field plowing. This work motivated the present experimental investigation of the influence of plow handle design and farmer whole-body posture on grip force and arm muscle activity. A total of 24 experienced farmers performed a simulated plowing task, including walking on even and uneven ground while rolling a tiller equipped with conventional horizontal and proposed vertical handles. Results revealed the proposed handles, designed to promote neutral wrist posture, to increase upper-arm muscle use between 47% and 70% across ground types, as compared with conventional handles. The ratio of grip force to forearm muscle activity (or efficiency in muscle use) increased from 1.85 when using conventional handles on uneven ground to 2.16 when using the proposed handles with symmetrical body posture on even ground. However, participants perceived higher discomfort when using the proposed handles, as they were accustomed to the conventional design. PRACTITIONER SUMMARY: The findings of this work may be used to educate farmers on the potential for hand and arm injury in rice cultivation activities. Results may also provide a basis for redesign of existing tiller handles to promote neutral wrist posture, greater efficiency in muscle use and machine control.