We refer to repetitive movements as those performed in activities that are generally repeated in short cycles, involving rapid efforts or movements of muscle groups, bones, joints, tendons, ligaments, and nerves in a part of the body, usually the upper limbs. According to the UNE EN 1005-5 standard, a task is repetitive when it is characterized by repeated work cycles. That is, repetitiveness is a characteristic of the task that causes the worker who performs it to continually repeat the same work cycle, technical actions, and movements.
To identify whether a task is repetitive, or whether it is repetitive but not risky, the UNE EN 1005-5 standard indicates that there is no risk of repetitiveness if:
The task is not characterized by work cycles.
The task is characterized by work cycles, but perceptive or cognitive activities clearly prevail, and movements of the upper limbs are residual.
Check List OCRA allows assessing the risk associated with repetitive work. The method measures the level of risk based on the probability of developing musculoskeletal disorders within a certain time, focusing on assessing the risk in the upper limbs of the body.
Many types of tasks, for example, those performed on an assembly line, force workers to perform repetitive movements that can sometimes lead to health problems. Excessive intensity, duration, or frequency of repetitive movements have harmful effects on health, which are exacerbated by maintaining forced postures, exerting force, or the absence of breaks that allow muscle recovery.
Most musculoskeletal disorders due to repetitive movements (such as tendonitis or carpal tunnel syndrome) appear gradually after long periods of exposure to overly demanding working conditions.
Check List OCRA is a tool derived from the OCRA method developed by the same authors. The OCRA method (Occupational Repetitive Action) takes into account the risk factors recommended by the IEA (International Ergonomics Association): repetitiveness, inappropriate or static postures, forces, forced movements, and lack of breaks or recovery periods, assessing them over the worker's activity time. In addition, it considers other influential factors such as vibrations, exposure to cold, or work rhythms. Therefore, there is international consensus on using the OCRA method for assessing the risk of repetitive work in the upper limbs, and its use is recommended in the ISO 11228-3 and EN 1005-5 standards.
Despite being the reference method for evaluating repetitive work, applying the OCRA method is complex and labor-intensive. The level of detail in OCRA results is directly proportional to the amount of required information and the complexity of the necessary calculations. The abbreviated Check List OCRA method allows for obtaining a basic risk assessment result for repetitive movements of the upper limbs with less effort, highlighting the urgency of conducting more detailed studies. There is a high correlation between the results obtained by both methods, making Check List OCRA the most suitable tool for an initial risk assessment, as stated in the ISO/NP TR 12295.
Remember...
According to the UNE EN 1005-5 standard, a task is repetitive when it is characterized by repeated work cycles.
Technical actions are elementary manual actions needed to complete operations within the work cycle, such as holding, turning, pushing, cutting...
A Work cycle is a sequence of technical actions that are always repeated in the same way.
The Work cycle time is the time interval from the moment the operator starts a work cycle until the same work cycle begins again.
The Technical action frequency is the number of technical actions performed per unit of time (usually in a minute).
Remember...
The Check List OCRA is a tool derived from the OCRA method.
Check List OCRA is the most suitable tool for conducting an initial risk assessment for repetitive work.
It considers risk factors such as: repetitiveness, inappropriate or static postures, forces, forced movements, lack of breaks, organizational factors, and environmental factors.
The Check List OCRA conducts a detailed analysis of many of the risk factors present in tasks performed at the workplace. To determine the risk level, different factors are analyzed independently, weighing their evaluation by the amount of time each factor is present within the total task duration. This way, risk factors are scored using scales that may differ for each factor. The most common scales range from 1 to 10, but others may reach higher values. From the scores of each factor, the Check List OCRA Index (OCLI) is obtained, a numerical value that allows classifying the risk as Optimal, Acceptable, Very Low or Uncertain, Unacceptable Mild, Unacceptable Moderate, or Unacceptable High. Based on this risk classification, corrective actions are suggested, such as improving the workstation, requiring medical supervision, or providing specific training for workers to occupy the workstation.
In general, the method assesses the risk of workstations considering a generic occupation of 8 hours per day (full-day risk). However, a worker may occupy the workstation for fewer hours, occupy multiple workstations in one day, or rotate between several workstations. In these cases, the risk for the worker can be determined by calculating the full-day risk of the workstations they occupy and weighing them by the time spent in each workstation. Thus, the method allows evaluating the risk associated with a workstation, a set of workstations, and, by extension, the exposure risk for a worker who occupies a single workstation or rotates among several workstations.
Time consideration is crucial in the Check List OCRA method. The importance of risk factors is assessed by considering the duration they are present in the activity carried out at the workstation. Furthermore, not all tasks performed at the workstation need to be necessarily repetitive, so the method takes into account the actual net duration of repetitive work. On the other hand, the actual occupation time of the workstation by the worker and the duration of breaks and rest periods are also considered in the analysis.
Another important feature of Check List OCRA is its simplicity and quick application compared to the OCRA method. Evaluating a workstation with a 15-second work cycle can be completed in 3-4 minutes. For a 15-minute cycle, the evaluation time may be approximately 30 minutes, including additional tasks for recording information (risk maps, software, videos, etc.).
Moreover, calculating risk factors independently provides scores for each factor, allowing the evaluator to understand how much they contribute to the total risk and guide them in the process of improving the conditions of the workstation.
Remember...
To carry out an evaluation of a workstation, the following should be considered:
Work time organization: the time the worker occupies the workstation during the day, and breaks and non-repetitive tasks. Recovery periods: periods during which one or more muscle groups involved in the movement remain entirely at rest. Frequency and type of actions: Work Cycle time, number and type of Technical Actions in a Work Cycle. Postures adopted: primarily considering the shoulder, elbow, wrist, and grips, as well as the presence of stereotyped movements. Forces exerted: this information is necessary only if forces are exerted with the hands or arms repeatedly at least once every few cycles. Additional risk factors: such as the use of personal protective equipment, impact, exposure to cold, vibrations, or inadequate work pace.
The application of the method aims to determine the Check List OCRA Index (OCLI) value and, based on this value, classify the risk as Optimal, Acceptable, Very Low, Low, Medium, or High. The OCLI is calculated using the following equation:
OCLI = ( FR + FF + FFz + FP + FC ) · DM
Check List OCRA Index (OCLI)
The value of OCLI is the result of adding five factors, subsequently multiplied by the duration multiplier (DM). As a preliminary step to calculating each factor and the duration multiplier, it is necessary to know, based on the work organization data, the net time of repetitive work and the net work cycle time.
In the following sections, we will explain how to calculate the Net Time of Repetitive Work (NTRW), the Net Cycle Time (NTC), and each of the factors and multipliers of the equation.
As a preliminary step to calculating the different factors and multipliers to obtain the Check List OCRA Index, it is necessary to calculate the Net Time of Repetitive Work (NTRW) and the Net Time of the Work Cycle (NTC).
The NTRW is the time during which the worker is at the workstation performing exclusively repetitive activities. That is, the time or duration of the work shift minus the time spent on non-repetitive activities such as break time, the time the worker spends on other non-repetitive tasks, rest periods, and other times of inactivity.
NTRW = DT - [ NRT + P + A ]
Net Time of Repetitive Work (NTRW)
In this equation, DT represents the duration in minutes of the shift or the time the worker occupies the workstation during the day. NRT is the non-repetitive work time in minutes, which is the time the worker spends on non-repetitive tasks such as cleaning, restocking, etc. P is the duration in minutes of the breaks the worker takes while occupying the workstation. A is the duration of the lunch break in minutes.
Once the NTRW is known, it is possible to calculate the Net Time of the Work Cycle. The NTC could be defined as the work cycle time if only the repetitive tasks performed at the workstation were considered.
NTC = 60 · NTRW / NC
Net Time of the Work Cycle (NTC)
The NTC will be expressed in seconds, and in this equation, NC is the number of work cycles that the worker performs at the workstation.
Remember...
The NTRW is the time or duration of the work shift at the workstation minus the breaks, the non-repetitive tasks performed at the workstation, rest periods, and other times of inactivity.
Break time should include both official breaks (those recognized by the company and to which the worker is entitled) and unofficial breaks (those not officially recognized by the company and taken at the worker's discretion).
You may be interested in...
To find out NC (the number of work cycles the worker performs at the workstation), you can do the following:
If the worker produces one piece per cycle, NC will be equal to the number of pieces produced.
If the worker produces x pieces per cycle, NC will be equal to the number of pieces produced divided by x.
Once the NTRW and NTC are known, we will proceed to calculate the factors and multipliers of the calculation equation for the OCLI.
The existence of adequate recovery periods after a period of activity allows the recovery of bone and muscle tissues. If there is not enough recovery time after the activity, the risk of suffering from musculoskeletal disorders increases. This factor of the OCRA Check List Index calculation equation assesses whether the recovery periods in the evaluated workstation are sufficient and conveniently distributed. The frequency of recovery periods, their duration, and distribution throughout the repetitive task will determine the risk due to the lack of rest and consequently the increase in fatigue.
To assess the recovery periods, the OCRA Check List measures the deviation of the actual situation in the workstation compared to an ideal situation. An ideal situation is considered to be one where there is a break of at least 8/10 minutes every hour (including the lunch break) or the recovery period is included in the work cycle, meaning the proportion between repetitive work and recovery is 50 minutes of repetitive task for every 10 minutes of recovery (the proportion between repetitive work and recovery period is 5:1).
Remember, a recovery period is...
...the time during which one or several muscle groups involved in the movement remain completely at rest. Examples of recovery periods are lunch breaks, visual control tasks, work breaks (official or not), tasks that allow rest for the muscle groups used in previous tasks (alternatively pushing objects with one arm and then the other), etc...
To calculate the value of the FR, you must use Table 1. This table presents possible situations regarding recovery periods, and you should choose the one most similar to the actual situation of the workstation.
| Recovery Period Situation | Score |
|---|---|
| - There is an interruption of at least 8 minutes every working hour (including lunch break). - The recovery period is included in the work cycle (at least 10 consecutive seconds out of every 60, in all cycles throughout the entire shift) |
0 |
| - There are at least 4 interruptions (in addition to the lunch break) of at least 8 minutes in a 7-8 hour shift. - There are 4 interruptions of at least 8 minutes in a 6-hour shift (without a lunch break). |
2 |
| - There are 3 breaks, of at least 8 minutes, in addition to the lunch break, in a 7-8 hour shift. - There are 2 breaks, of at least 8 minutes, in a 6-hour shift (without a lunch break). |
3 |
| - There are 2 breaks, of at least 8 minutes, in addition to the lunch break, in a 7-8 hour shift. - There are 3 breaks (without a lunch break), of at least 8 minutes, in a 7-8 hour shift. - There is 1 break, of at least 8 minutes, in a 6-hour shift. |
4 |
| - There is 1 break, of at least 8 minutes, in a 7-hour shift without a lunch break. - In an 8-hour shift, there is only the lunch break (the lunch break is included in the working hours). |
6 |
| - There are no real breaks, except for a few minutes (less than 5) in a 7-8 hour shift. |
10 |
Unlike the other factors in the equation, where the score depends on the time spent performing the activity, the score for this factor depends on the total duration of the workstation occupation.
If it is not possible to find the specific situation of the evaluated workstation among those proposed in Table 1, the closest one should be chosen.
The frequency of repetitive movements influences the risk they pose to worker health. Therefore, a higher number of actions per unit of time, or a shorter time to perform a given number of actions, increases the risk.
To determine the value of the Frequency Factor, it is necessary to identify the type of technical actions performed in the workstation. There are two types of technical actions: static and dynamic. Dynamic technical actions are characterized by being brief and repeated (periodic succession of short-duration tensions and relaxations of the acting muscles). Static technical actions are characterized by having a longer duration (continuous and sustained muscle contraction for 5 seconds or more). Both types of technical actions should be analyzed separately. In addition, the actions performed by both arms will be analyzed separately, and a different evaluation should be carried out for each arm if necessary.
After analyzing both types of technical actions, Table 2 will be used to obtain the score for dynamic technical actions (DTA), and Table 3 to obtain the score for static technical actions (STA):
Remember, a Technical Action is...
...one or several movements needed to complete a simple operation involving one or several upper limb joints.
Examples of Technical Actions are: moving objects, reaching for objects, grasping an object with the hand or fingers, passing an object from the right hand to the left and vice versa, placing an object or tool in a specific location to perform an activity, pushing or pulling an object requiring force, pressing buttons or levers with the hand or fingers to activate a tool, bending, brushing, rotating, etc...
| Dynamic Technical Actions | DTA |
|---|---|
| Arm movements are slow (20 actions/minute). Frequent small pauses are allowed. |
0 |
| Arm movements are not too fast (30 actions/minute). Small pauses are allowed. |
1 |
| Arm movements are quite fast (more than 40 actions/minute). Small pauses are allowed. |
3 |
| Arm movements are quite fast (more than 40 actions/minute). Only occasional and irregular small pauses are allowed. |
4 |
| Arm movements are fast (more than 50 actions/minute). Only occasional and irregular small pauses are allowed. |
6 |
| Arm movements are fast (more than 60 actions/minute). The lack of pauses makes it difficult to maintain the rhythm. |
8 |
| Arm movements are performed at a very high frequency (70 actions/minute or more). Pauses are not allowed. |
10 |
| Static Technical Actions | STA |
|---|---|
| Holding an object for at least 5 consecutive seconds while performing one or more static actions for 2/3 of the cycle time (or observation time). |
2.5 |
| Holding an object for at least 5 consecutive seconds while performing one or more static actions for 3/3 of the cycle time (or observation time). |
4.5 |
With the values of DTA and STA known, the FF factor score is obtained as the maximum of the two values:
FF = Max ( DTA ; STA )
Frequency Factor (FF)
Although technical actions are generally identified in the OCRA Checklist application, Table 4 compiles some common technical actions that can serve as a guide for their identification:
| Technical Action | Definition and Criteria |
|---|---|
| MOVE |
Transport an object to a specific location using the upper limbs (without walking). |
| REACH | Extend the hand to a predetermined location. Reaching for an object should be considered an action only when the object is placed beyond the length of the fully extended upper limb and is not reachable by walking, so the operator must move the trunk and shoulders to reach the object. If the workplace is used by men and women, or only by women, the measure of the length of the fully extended upper limb corresponds to 50 cm (5th percentile of women), and this length should be used as a reference. Alternatively, it will be considered a technical action when the object is located outside the reach of the working area limits (A2, B2, C2) specified in the ISO 14738:2002 standard. |
| GRASP/GRAB | Hold an object with the hand or fingers to perform an activity or task. |
| TRANSFER HAND TO HAND | The actions of grasping an object with one hand, passing it to the other hand, and grasping it again with the other hand are considered two separate technical actions: one for the right hand and one for the left hand. |
| PLACE | Position an object or tool at a predetermined point. SYNONYMS: position, support, put, arrange, leave, reposition, replace. |
| INSERT/REMOVE | The action of inserting or removing should be considered a technical action when the use of force is required. SYNONYMS: Extract, insert. |
| PUSH/PULL | These should be counted as actions since they result from the application of force, even if it is minimal, with the intention
of obtaining a specific outcome. SYNONYMS: Press, disconnect parts. |
| ACTIVATE | Should be considered an action when starting a tool requires the use of a button or lever by parts of the hand or by one or more fingers.
If the activation is done repeatedly without changing the tool, consider one action for each activation. SYNONYMS: press button, lower lever. |
| TRANSPORT | If an object weighing 3 kg or more is transported at least 1 meter, the upper limb supporting the weight performs the technical action of "transporting." One meter signifies a genuine transport action (two steps). |
| SPECIFIC ACTIONS | Specific actions that are part of a particular process, for example: Bend, fold, curve, deflect, squeeze, rotate, turn, adjust, shape, lower, reach, strike, brush (count each brush stroke on the part to be painted), grate (count each stroke on the part to be grated), smooth, polish (count each stroke on the part to be polished), clean (count each stroke on the part to be cleaned), hammer (count each of the strikes), throw, etc. Each of these actions should be described and counted once for each repetition, for example, turning twice = 2 technical actions. |
| The following are not technical actions: | |
| RELEASE | If an object that is no longer needed is simply dropped by opening the hand or fingers, then the action should not be considered a technical action (it is a passive restitution or a dropping). |
| WALK, VISUAL CONTROL | They should not be considered technical actions as they do not involve any upper limb activity. |
The OCRA Checklist considers this factor significant only if force is exerted with the arms and/or hands at least once every few cycles. Additionally, the application of such force must be present throughout the repetitive movement. Otherwise, it will not be necessary to calculate FFz, assigning it a value of 0.
The calculation of the Force Factor is based on quantifying the effort required to carry out technical actions in the workplace. To do this, first identify the actions that require the use of force, such as the following.
Once the actions performed at the workplace requiring force application are identified, the effort required to perform each will be determined. The Borg CR-10 scale of perceived exertion can be used for this purpose. If no effort is perceived or it is weak, it will not be considered. If the effort is moderate (3 or 4 on the CR-10 scale), it will be considered Moderate Force. If the perceived effort is strong or very strong (5 to 7 on the CR-10 scale), the force will be considered Intense. If the effort is greater (more than 7 on the Borg CR-10 scale), the force will be considered Near Maximum.
Next, a score will be obtained for each of the identified actions based on the intensity of the effort (moderate, intense, near maximum) and the percentage of the work cycle time in which the effort is performed. To do this, the Table 5 will be used. Finally, the Force Factor (FFz) value will be obtained by adding all the scores obtained.
Remember...
The Force Factor should be calculated only if force is exerted with the arms and/or hands at least once every few cycles and if the force application is present throughout the repetitive movement.
Remember...
The Borg CR-10 scale allows measuring the intensity of an effort by observing the subject's expressions during the effort. The Force Factor in OCRA depends on the intensity of the effort according to the following Table:
Effort Score OCRA FFz None 0
Not considered Very weak 1
Weak 2
Moderate 3
Moderate force 4
Strong 5
Intense force 6
Very strong 7
Near maximum 8
Near maximum force 9
10
| Moderate force | Intense force | Near maximum force | |||
|---|---|---|---|---|---|
| Duration | Points | Duration | Points | Duration | Points |
| 1/3 of the time | 2 | 2 sec. every 10 min. | 4 | 2 sec. every 10 min. | 6 |
| 50% of the time | 4 | 1% of the time | 8 | 1% of the time | 12 |
| > 50% of the time | 6 | 5% of the time | 16 | 5% of the time | 24 |
| Almost all the time | 8 | > 10% of the time | 24 | > 10% of the time | 32 |
The OCRA Checklist considers, as a risk-increasing factor, the maintenance of forced postures and the performance of forced movements in the upper limbs. The analysis includes the shoulder, the elbow, the wrist , and the hand. In addition, the existence of movements that are repeated identically within the work cycle (stereotyped movements) is considered.
Regarding the shoulder, the position of the arm in terms of flexion, extension, and abduction should be assessed using Table 6, obtaining the score PHo. For the elbow, flexion, extension, and pronosupination will be assessed (using Table 7) to obtain the score PCo. Table 8 allows for the assessment of the existence of forced postures and movements of the wrist (flexions, extensions, and radio-ulnar deviations), determining the score PMu. Finally, the type of grip performed by the hand is carried out by consulting Table 9 which allows obtaining the score PMa. The grip performed will be considered when it is one of these types: pinch grip or pincer, hook grip, or palmar grip.
Remember...
OCRA Checklist assesses postures and movements performed with the shoulder, the elbow, the wrist, and the hand. In addition, it considers stereotyped movements.
Stereotyped movements are those movements that are repeated identically or very similarly within the work cycle.
At this point, a score will have been obtained for each joint (PHo, PCo, PMu, PMa). To assess the existence of stereotyped movements, Table 10 is used, through which the score PEs is obtained. This score depends on the percentage of the cycle time that these movements occupy and the duration of the cycle time. Note that if they do not exist, or stereotyped movements occupy less than 2/3 of the working time, the score for PEs is 0.
Once the previous 5 scores have been obtained, the value of the Posture and Movement Factor (FP) can be calculated. To do this, the highest score obtained for the shoulder, elbow, wrist, and hand will be added to the score obtained for the stereotyped factors according to the equation:
FP = Max ( PHo ; PCo ; PMu ; PMa ) + PEs
Posture and Movement Factor (FP)
| Shoulder postures and movements | PHo |
|---|---|
| Arm/s without support and slightly raised more than half the time | 1 |
| Arm held at shoulder height and without support (or in another extreme posture) about 10% of the time | 2 |
| Arm held at shoulder height and without support (or in another extreme posture) about 1/3 of the time | 6 |
| Arm held at shoulder height and without support more than half the time | 12 |
| Arm held at shoulder height and without support all the time | 24 |
| (*) the scores will be doubled if hands remain above head height. | |
| Elbow postures and movements | PCo |
|---|---|
| Elbow makes sudden movements (flexion-extension or extreme pronation-supination, jerks, hits) at least a third of the time | 2 |
| Elbow makes sudden movements (flexion-extension or extreme pronation-supination, jerks, hits) more than half the time | 4 |
| Elbow makes sudden movements (flexion-extension or extreme pronation-supination, jerks, hits) almost all the time | 8 |
| Wrist postures and movements | PMu |
|---|---|
| Wrist remains bent in an extreme position or adopts forced postures (high degree of flexion-extension or lateral deviation) at least 1/3 of the time | 2 |
| Wrist remains bent in an extreme position or adopts forced postures (high degree of flexion-extension or lateral deviation) more than half the time | 4 |
| Wrist remains bent in an extreme position, all the time | 8 |
| Grip Duration | PMa |
|---|---|
| About 1/3 of the time | 2 |
| More than half the time | 4 |
| Almost all the time. | 8 |
| (*) Grip will only be considered if it is one of these types: pinch or pincer grip, hook grip, or palmar grip. | |
| Stereotyped Movements | PEs |
|---|---|
| - Identical movements of the shoulder, elbow, wrist, or fingers are repeated at least 2/3 of the time - Or the cycle time is between 8 and 15 seconds. |
1.5 |
| - Identical movements of the shoulder, elbow, wrist, or fingers are repeated almost all the time - Or the cycle time is less than 8 seconds |
3 |
In addition to the risk factors considered so far, the OCRA Checklist takes into account other possible complementary factors that can affect the overall risk depending on their duration or frequency. Such risk factors can include the use of personal protective equipment such as gloves, the use of tools causing vibrations or skin contractions, the type of work pace (imposed by the machine), etc.
Additional factors are grouped into two types: physical-mechanical factors and factors derived from socio-organizational aspects of work. To obtain the score for the Additional Risk Factors (FC), choose an option from Table 11 to obtain the Ffm score for physical-mechanical factors. Then, find the appropriate option for socio-organizational factors in Table 12 to obtain the Fso score. Finally, add both scores to get the FC:
FC = Ffm + Fso
Additional Risk Factors (FC)
| Socio-organizational factors | Fso |
|---|---|
| Work pace is partially determined by the machine, with short periods of time when the work pace can be slowed down or sped up | 1 |
| Work pace is entirely determined by the machine | 2 |
| Physical-Mechanical Factors | Ffm |
|---|---|
| Inappropriate gloves (interfering with the gripping dexterity required by the task) are used more than half of the time | 2 |
| The activity involves striking (with a hammer, hitting with a pickaxe on hard surfaces, etc.) with a frequency of 2 times per minute or more | 2 |
| The activity involves striking (with a hammer, hitting with a pickaxe on hard surfaces, etc.) with a frequency of 10 times per hour or more | 2 |
| Exposure to cold (below 0°C) more than half of the time | 2 |
| Tools producing low/medium level vibrations are used for 1/3 of the time or more | 2 |
| Tools producing high-level vibrations are used for 1/3 of the time or more | 2 |
| The tools used cause skin compression (redness, calluses, blisters, etc.) | 2 |
| Precision tasks are performed more than half of the time (tasks on areas less than 2 or 3 mm) | 2 |
| Several concurrent additional factors are present, and they occupy more than half of the time | 2 |
| Several concurrent additional factors are present, and they occupy all the time | 3 |
| (*) If several factors concur, one of the last two options should be chosen. |
In the calculation of all the previous factors, a risk exposure time of 8 hours has been considered. That is, the risk has been assessed for an 8-hour shift in the evaluated workstation, where all the work cycle time is dedicated to repetitive work. However, the work shift may be shorter than 8 hours, and not all the time is dedicated to repetitive work if there are breaks, rest periods, and non-repetitive work. To obtain the risk level considering exposure time, the duration multiplier (DM) must be calculated. Unlike the other factors, which are added, DM will be multiplied by the sum of the remaining factors.
DM is calculated using Table 13 and depends on the value of the Net Time of Repetitive Work (NTRW) calculated previously. As can be seen in Table 13, if NTRW is equal to 480 minutes (8 hours), DM takes the value of 1. If the Net Time of Repetitive Work is less than 480 minutes, DM decreases, so the OCRA Checklist Index will be lower, while it will increase if NTRW is longer than 8 hours. The duration values less than 60 minutes that appear in the second part of Table 13 are used in multitask analysis where tasks are brief.
| Net Time of Repetitive Work (NTRW) in minutes | DM |
|---|---|
| 60-120 | 0.5 |
| 121-180 | 0.65 |
| 181-240 | 0.75 |
| 241-300 | 0.85 |
| 301-360 | 0.925 |
| 361-420 | 0.95 |
| 421-480 | 1 |
| 481-539 | 1.2 |
| 540-599 | 1.5 |
| 600-659 | 2 |
| 660-719 | 2.8 |
| ≥720 | 4 |
| Net Time of Repetitive Work (NTRW) in minutes (For multitask analysis only) | DM |
|---|---|
| ≤1.87 | 0.01 |
| 1.88-3.75 | 0.02 |
| 3.73-7.5 | 0.05 |
| 7.6-15 | 0.1 |
| 15.1-30 | 0.2 |
| 31-59 | 0.35 |
Once all factors and the duration multiplier have been calculated, the OCRA Checklist Index can be determined using the equation:
ICL = ( FR + FF + FFz + FP + FC ) · DM
OCRA Checklist Index (ICL)
With the calculated value of the OCRA Checklist Index, the Risk Level and Recommended Action can be obtained using Table 14.
| OCRA Checklist Index | Risk Level | Recommended Action | Equivalent OCRA Index |
|---|---|---|---|
| ≤ 5 | Optimal | Not required | ≤ 1.5 |
| 5.1 - 7.5 | Acceptable | Not required | 1.6 - 2.2 |
| 7.6 - 11 | Uncertain | New analysis or job improvement recommended | 2.3 - 3.5 |
| 11.1 - 14 | Mildly Unacceptable | Job improvement, medical supervision, and training recommended | 3.6 - 4.5 |
| 14.1 - 22.5 | Moderately Unacceptable | Job improvement, medical supervision, and training recommended | 4.6 - 9 |
| > 22.5 | Highly Unacceptable | Job improvement, medical supervision, and training recommended | > 9 |
There is a proven correlation between the risk index obtained through the OCRA Checklist and the OCRA Index (obtained with the OCRA method). The Equivalent OCRA Index shown in Table 14 is the value of the OCRA method index equivalent to the one obtained with the OCRA Checklist.
It may be useful to calculate the OCRA Checklist Index for a group of jobs or for a worker who rotates among various workstations. In the first case, to calculate the OCRA Checklist Index for a group of jobs, it is necessary to calculate the Index for each of the workstations individually, and then calculate the average of the obtained values.
OCLImean = ( OCLI1 + OCLI2 + ... + OCLIn ) / n
Average OCRA Checklist Index for n workstations
When a worker rotates among various workstations, it is possible to calculate the OCRA Checklist Index by knowing the Index of each workstation and the percentage of the workday each one occupies. In this case, two situations must be distinguished. When the worker changes workstations at least once per hour, the following equation will be used:
OCLImult = ( OCLI1 • %P1 + OCLI2 • %P2+ ... + OCLIn • %Pn)
Multitask OCRA Checklist Index for n workstations
When shifts at each workstation last longer than one hour, the previous equation is not applicable because it underestimates the actual risk, requiring a more complex calculation procedure.
Although it is a reference method for assessing the risk of repetitive work, the OCRA Checklist has certain limitations that must be considered in its application.
Its fundamental limitation is its preliminary nature. If the assessment detects the presence of risks, it must be completed with a more in-depth analysis, for example, using the full version of the OCRA method.
In addition to this fundamental limitation, there are some minor considerations:
Remember...
If the evaluation conducted with the OCRA Checklist detects the presence of risks, it should be completed with a more in-depth analysis, for example, using the full version of the OCRA method.
Colombini D., Occhipinti E., Grieco A., 2002. Risk assessment and management of repetitive movements and exertions of upper limbs. Elsevier. pp. 111-117.
Diego-Mas, J.A., Poveda-Bautista, R. and Garzon-Leal, D.C., 2015. Influences on the use of observational methods by practitioners when identifying risk factors in physical work. Ergonomics, 58(10), pp. 1660-70.
Occhipinti E., 1998. OCRA: a concise index for the assessment of exposure to repetitive movements of the upper limbs. Ergonomics, 41(9):1290-311.
International Standard, NEN-EN-ISO 11228-3. Ergonomics - Manual handling - Part 3: Handling of low loads at high frequency. 2007.
Instituto Nacional de Seguridad e Higiene en el Trabajo, Ministerio de Empleo y Seguridad Social (National Institute for Safety and Hygiene at Work, Ministry of Employment and Social Security). ,Repetitive tasks II: risk assessment for the upper extremity
Diego-Mas, Jose Antonio. Repetitive motion risk assessment using the Ocra Check List. Ergonautas, Universidad Politécnica de Valencia, 2023. Disponible online: https://www.ergonautas.upv.es/ergoniza/app_en/land/index.html?method=ocra
A cloud based software that integrates more than 20 tools for managing the ergonomics of the workstations in your company.
Evaluate all ergonomic risk factors of the workstations in your company: inadequate postures, repetitive movements, load handling, thermal environment...
Generate fully customizable reports in Microsoft Word or Adobe Pdf format.
In a multiuser environment so that your company can have access to your data everywhere.
You only need a free account on Ergoniza
ERGONIZA helps you manage the ergonomics of the workstations of your companies. Evaluate all the risk factors present in the workstations, manage the evaluations, and obtain editable and customizable reports.
You only need to register as a user of ERGONIZA to start testing.
Sign UpUnlock the full potential of Ergoniza. By becoming a Pro User you'll have access to all of Ergoniza and be able to use all of the online software without restrictions or time limits. You'll be able to use the results of evaluation methods and tools in your professional activity. You'll be able to print the results reports in pdf or Word and save your studies in files to open them later.
To register as a Pro user, you must first login to Ergoniza.
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(**) The price in american dollars has been calculated at the current exchange rate and may vary.
is a web by . Ergonautas is the specialized website in occupational ergonomics and ergonomic assessment of workstations at the . Ergonautas aims to be a useful support tool for the Occupational Risk Prevention and Ergonomics professional and people in training, providing rigorous technical information on occupational ergonomics, online tools for its application, research, training, and participation forums.
Ergonautas is formed by a large human team. In addition to technicians and programmers, the Ergonautas team is made up of researchers and professors from the Polytechnic University of Valencia. The team, led by José Antonio Diego Más, is at the forefront of research and teaching in ergonomics, teaching in official degrees and master's degrees, and developing research projects in the field of ergonomics and new technologies oriented towards humans.
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