OCRA: a concise index for the assessment of exposure to repetitive movements of the upper limbs

Abstract

In the light of data and speculation contained in the literature, and based on procedures illustrated in a previous research project in which the author described and evaluated occupational risk factors associated with work-related musculoskeletal disorders of the upper limbs (WMSDs), this paper proposes a method for calculating a concise index of exposure to repetitive movements of the upper limbs. The proposal, which still has to be substantiated and validated by further studies and applications, is conceptually based on the procedure recommended by the NIOSH for calculating the Lifting Index in manual load handling activities. The concise exposure index (OCRA index) in this case is based on the relationship between the daily number of actions actually performed by the upper limbs in repetitive tasks, and the corresponding number of recommended actions. The latter are calculated on the basis of a constant (30 actions per minute), which represents the action frequency factor; it is valid--hypothetically--under so-called optimal conditions; the constant is diminished case by case (using appropriate factors) as a function of the presence and characteristics of the other risk factors (force, posture, additional elements, recovery periods). Although still experimental, the exposure index can be used to obtain an integrated and concise assessment of the various risk factors analysed and to classify occupational scenarios featuring significant and diversified exposure to such risk factors.

Self-administered questionnaire and direct observation by checklist: Comparing two methods for physical exposure surveillance in a highly repetitive tasks plant

“…Moreover, checklists are standardized but simplistic methods, compared to other observational methods: only the most frequent situations were explored with dichotomous exposure items, and without any weighting of these (some situations are probably worse than others). Several other checklists have been developed to assess UWMSD risk (Li and Buckle 1999), beyond the ones focused on posture (Karhu et al 1977;McAtamney and Nigel 1993): we could mention for instance the Concise Exposure Index (OCRA) developed in 1998 to quantify worker exposure to tasks involving repetitive movement of the upper limb (Occhipinti 1998), the Quick Exposure Checklist (QEC) developed also in 1998, which represents a UWMSD assessment checklist tool (Li and Buckle 1998) (Silverstein 1997), or standards (IS0 11226). However, when the study was designed, most of the existing checklists had not yet been validated for surveillance purposes (Kilbom 1994;Li and Buckle 1999).…”

Measurement Consistency Among Observational Job Analysis Methods During an Intervention Study

“…OCRA was chosen because it takes into account a wide array of risk factors, such as repetition, frequency, force, posture (hands, wrists, elbows and shoulders), and movement, recovery and additional factors (precision, mechanical pressure, rapid movement, etc.) [3]. OCRA considers the impact of all tasks in a work shift and separates the right and left sides of the body in two indices [3].…”

“…To date, many observational methods have been published to evaluate the exposure to MSD risk factors and guide the appropriate corrective actions, e.g., RULA [2], OCRA [3] and QEC [4]. These methods can be used for exposure surveillance of risk factors such as awkward joint postures, force requirements, etc., and can be used to evaluate the reduction in the exposure to risk factors after ergonomics modifications.…”

Design of assembly lines with the concurrent consideration of productivity and upper extremity musculoskeletal disorders using linear models

“…The cumulative trauma disorder (CTD) risk assessment model for the upper extremities was developed by (Seth, Lee Weston and Freivalds 1999, 281-291). Occupational repetitive actions index (OCRA) was developed by (Occhipinti 1998(Occhipinti , 1290(Occhipinti -1311. The rapid entire body assessment (REBA) was designed for reducing WMSDs by (Hignett and McAtamney 2000, 201-206).…”