What is the OCRA method?
OCRA was first presented in 1998 and has been developed and validated in successive epidemiological studies. Its approach differs from that of postural methods: instead of scoring a posture, it counts technical actions, understood as the elementary operations that the upper limb performs within the work cycle.
Exposure is expressed as an index calculated by dividing the total number of technical actions actually performed during the shift by the total number of technical actions recommended for that position. This recommended number is derived from a reference frequency corrected for force, posture, lack of recovery periods, task duration, and other additional factors.
The National Institute for Occupational Safety and Health describes it in Technical Prevention Note 629 and in its document on risk assessment for the upper limb in repetitive tasks.
What it evaluates and what it does not evaluate
- Evaluate. The exposure of the upper limb to repetitive movements , integrating frequency of actions, force, postures and forced movements, lack of recovery and complementary factors.
- Evaluate the entire shift. The result refers to the workday and the organization of the work, not a single moment.
- It does not assess heavy lifting, pushing and pulling, or exposure to vibrations, which have their own methods.
- It is not a postural method in the strict sense: posture intervenes as a corrective factor, not as the main object.
- It does not diagnose. A high index indicates an exposure that needs to be corrected, not an existing pathology.
Scope of application
OCRA is designed for jobs with short, repetitive cycles throughout a shift: assembly line work, product handling and packaging, food preparation and cutting, garment making, or finishing line work. Its application is time-consuming: for a task with a thirty-second cycle, it may take between two and three hours to analyze, including video recording.
For this reason, it’s advisable to first verify that the job actually presents a risk of musculoskeletal disorders due to repetitive motion, by first applying a checklist that identifies the jobs and operations that warrant detailed analysis. The OCRA checklist fulfills this function.
OCRA index and OCRA checklist
Both tools belong to the same family and are used at different times in the process, so they should not be confused or treated as independent methods.
- OCRA checklist. Abbreviated version, designed for screening and evaluating a large number of workstations. It assigns scores to lack of recovery, frequency, force, posture, and additional factors, and allows workstations to be ranked by priority.
- OCRA Index. Detailed version, which calculates the relationship between actions performed and recommended and requires a detailed analysis of the cycle, the organization of the shift and the breaks.
- Combined use. The usual practice is to screen using the checklist and reserve the index for positions that require it, or to verify the effect of a redesign.
Information needed to apply it
- Shift organization: duration, tasks, breaks, job changes and non-repetitive work.
- Duration of the cycle and description of the technical actions that comprise it.
- Frequency of actions per minute in each repetitive task.
- Applied force, estimated using a perceived exertion scale or by measurement where possible.
- Forced postures and movements of the shoulder, elbow, wrist and hand, with their relative duration within the cycle.
- Distribution of recovery periods throughout the shift.
- Additional factors such as vibrations, extreme precision, machine-imposed pace, or use of unsuitable gloves.
How to interpret the result
The exposure index is interpreted by zones. According to the classification compiled by the INSST, an index equal to or less than 1 corresponds to a situation with no risk; between 1.1 and 2 the risk is very low; between 2.1 and 3.9 the risk is low but may be significant, so health monitoring, training and improvement of conditions are necessary; from 4 onwards, the risk zone is entered, and the higher the value, the greater the risk, requiring the redesign of tasks and jobs.
The INSST document itself warns that the international standard recommended by OCRA subsequently modified these classification criteria, reducing the number of risk zones. When applying the method, it is advisable to explicitly state which classification criteria were used and which edition of the standard was consulted.
Limitations and situations in which it should not be used
- Applying it without specific training and without practice in task analysis: it is the most demanding method of those commonly used in physical ergonomics.
- Using it as a quick screening tool when what is appropriate is a checklist.
- Use it in non-repetitive, long-cycle or highly variable tasks, where counting technical actions loses its meaning.
- Transfer the result to factors that the method does not evaluate, such as lifting loads or hand-arm vibrations.
- Comparing indices calculated using different classification criteria without realizing it.
- Presenting the index as a regulatory exposure limit value, a condition it does not have in Spain.
Practical example
A canning plant reports wrist and elbow discomfort on the finishing line, with cycles of about twenty seconds and a rhythm dictated by the conveyor belt.
- Screening. The OCRA checklist is applied to the six stations on the line. Four are classified as low priority and two, lid placement and boxing, as high priority.
- Detailed analysis. The OCRA index is calculated for the two positions indicated, based on the cycle video and the actual shift organization.
- Measures. The frequency is reduced by rotating workers between tasks every ninety minutes, the lid is replaced with a less resistant format, and a short mid-morning break is added.
- Re-evaluation. The new calculation places both positions in a lower risk zone, and monitoring of the health of exposed personnel is maintained.
Differences with other methods
- Compared to RULA and REBA. These score specific positions; OCRA counts technical actions and evaluates the entire shift.
- Compared to OWAS. OWAS describes the distribution of global postures by sampling, without addressing the frequency of upper limb actions.
- Compared to the NIOSH lifting equation. This applies to manual lifting of loads with two hands and returns a recommended weight limit.
- Compared to the OCRA checklist. The checklist is an abbreviated version of the same method, intended for screening, not a different method.
Technical and regulatory framework
- Law 31/1995, articles 15 and 16. It requires the assessment of unavoidable risks and the adaptation of work to the person.
- Royal Decree 39/1997, article 5. Requires evaluation procedures that provide confidence in their outcome.
- ISO 11228-3:2026 . Second edition of the international standard on repetitive movements and efforts of the upper limb, published in May 2026, replacing the 2007 edition in which OCRA was incorporated as a reference method.
- INSST portal on repetitive work . It brings together the criteria and technical materials applicable in Spain.
No Spanish regulation mandates OCRA. Its use is based on Article 5 of Royal Decree 39/1997 and its recognition in international technical standardization.
