Work Study and Ergonomics

Introduction

In general, the upper limb or distal upper extremity (DUE) includes the muscle forming the rounded contour of the shoulder to the hand which is called deltoid region. Therefore, DUEs are the limbs like armpit, upper and lower arm, elbow, wrist and hand. These are perceived to be more associated with nerve injury. The risk to these DUE disorders can be assessed using some qualitative and quantities methods. Moore and Garg (1995) proposed a method ‘The Strain Index’ to analyze jobs for risk of distal upper extremity disorders and to distinguish between jobs which are associated with distal upper extremity disorders from those which are not. However, Drinkaus et al. (2005) proposed that the Strain Index (SI) may be modified to estimate the risk of distal upper extremity injury. The SI was developed and validated using single task jobs. It was proposed that the SI would be more useful; however, if it could be extended to estimate the risk of a job with more than one task. Two methods were mentioned: the first is maximum task and the second is CARD (Cumulative Assessment of Risk to the Distal Upper Extremity) approach. Stephens et Al. (2009) evaluated the SI for various worksites with job titles including assemblers, painters and office workers (which performed very different tasks between the different worksites even with the same job titles), and some unique job titles to specific worksites such as hook fabricator and deck hand. These authors used different SI computation methods and resulted in significantly different SI scores along with different risk level classifications calculated by the different computation methods. Vishal et al. (1999) developed a cumulative trauma disorders (CTD) risk assessment model for predicting injury incidence rates. The model was found best suited for job tasks with cycle times greater than 4 sec. Moore and Garg (1998) evaluated the effectiveness of a corporate ergonomics programme that used a participatory approach to solving problems related to musculoskeletal hazards. The corporation experienced a significant decrease in the percentage of recordable disorders related to musculoskeletal risk factors, a marked decrease in the lost-time incidence rate, and a marked decrease in total and per capita annual workers' compensation costs. Garg et al. (2007) presented three different studies showing that the SI is capable of identifying jobs with no distal upper extremity morbidity as ‘safe’ and jobs with distal upper morbidity as ‘hazardous’.