Farheen Bano, Zulqernian Mallick & Abid Ali Khan International Journal of Ergonomics (IJEG), Volume (4) : Issue (1) : 2013 1 EMG Investigations Regarding Handle Size, Grip Force and Stroke Rotation In Screw Driving Farheen Bano farheenbano@gmail.com Department of Mechanical Engineering Jamia Millia Islamia New Delhi-110025. India Dr. Zulqernian Mallick zmallick2002@yahoo.co.in Department of Mechanical Engineering Jamia Millia Islamia New Delhi-110025. India Dr. Abid Ali Khan abida.khan@amu.ac.in Ergonomics Research Division, Department of Mechanical Engineering, Aligarh Muslim University, Aligarh-202002, UP, India Abstract The present study investigated the effect of handle size (35mm and 40mm), grip type (loose grip and tight grip) and supine stroke rotation (30⁰, 45⁰ and 60⁰) on electromyography i.e. EMG activity of forearm muscles for a screwing task in an experimental simulation. The eight participants performed the screw driving task for a 2 minutes duration (supination). The EMG activities of forearm muscles were recorded during this task. The muscles selected for EMG recording were FCR, FCU, FDS and ECRB muscles. The results showed that the flexor muscles were more activated than extensor muscles. Among giving conditions, 40mm handle size using loose grip with 60⁰ stroke was most comfortable. Keywords: Screw Driving Task, Stroke Rotation, EMG. 1. INTRODUCTION Hand tools are of primary focus in most of the industrial occupations. The industries primarily concerned with high percentage of injuries as found in literature [1]. Approximately 9% hand tool- related injuries were found out of all WMSDs in 23 states of the United States. Among all hand tool injuries reported by Aghazadeh and Mital [2] 79% are incurred by the use of non-powered hand tools. Screw driver is one of the most important hand tool used in many industries for assembly tasks. Many researchers conducted experiments on screw driving task [3], [4] and [5] and pneumatic/ electric screw drivers [6], [7] and [8]. Continuous efforts are made by researchers to have comfortable design of hand tools with reduced risk of WMSDs e.g. Kong and Lowe [9] investigated the handle diameters and orientations for evaluating maximum torque, perceived comfort, muscle activity and finger force for a torquing task. In another study, Kong et al. [10] evaluated three different shapes of handles specifically for screw driving using subjective discomfort rating and finger force. Chang et al. [6] studied the operation of in-line pneumatic screw driver affected by wearing gloves and wrist support in terms of hand transmitted vibration and EMG activity of flexor digitorum muscle. Chang and Wang [7] reported increased hand-arm stress while operating electric screw driver, investigations were based on finger force and EMG activity of the flexor digitorum muscle. These are not all but many more studies have worked on designing tools such as screw driver, power drill etc. However none of the study except Bano et al. [11] considered the torquing stroke rotation as independent variable and evaluated the effect of this variable either on discomfort or on EMG. The experiments shown in literature asked