The RULA Method

Rapid Upper Limb Assessment (RULA) method was designed to analyze the biomechanical/postural stresses on worker’s Upper limbs and to identify the muscular effort associated with a work posture. The RULA ergonomic assessment tool is in conformity with the European directive 90/270/EEC.

RULA uses a systematic process to evaluate required postures related to work cycle, muscle use frequency and forceful exertions.

The RULA assessment requires the determination of joint angles of different body parts (shoulder, elbow, wrist, trunk and neck). This method was developed to investigate the exposure to the individual risk factors assicoted with Musculoskeletal disorders (MSDs). Validated by several studies, RULA  method is used by many ergonomists around the world.

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THE RULA METHOD

Indications

The RULA method mainly evaluates the upper limbs (shoulder, elbow, wrist) but also the neck and trunk. It applies to tasks in which the worker’s uses mostly his upper limbs, with little or no movement. The postures are mainly studied, taking into consideration muscle use frequency and forceful exertions.

Restrictions & limits

  •  The RULA method is not recommended for evaluating manual handling tasks.
  • The RULA method mainly evaluates posture but takes into account muscle use and forceful exertions, however it focuses on the analysis of work postures.
  • It does not take into account the activity duration, the recovery period nor vibrations.
  • A separate assessment of right and left sides of the body is essential when using RULA. There is no specific way to obtain an overall result for the whole body.
  • The cumulative effects of all activities performed in a job or task are not taken into account.

Process

STEP 1 - Request analysis

Analysis of the request and development of criteria for work situations  choice to be observed

STEP 2 - Workstation observations

  • Observation of all workstation elements ( operator posture, tools used).

  • Identification of all possible interactions between the different elements.
  • Select the posture to be evaluated for the specific task.

STEP 3 - Task assessment

Evaluation of critical postures using RULA postural assessment method to estimate postural risk level.

STEP 4 -Processing of analysis results

Analysis of postural data in order to draw up a list of priorities and to seek solutions and proposals for improvement.

STEP 5 - Improvement solutions

Formulation of the improvements based on the analysis results and implementation of measures taking into account the identified risk factors.

STEP 6 - Evaluation of corrective measures

Once the changes have been made, reassess with the RULA assessment tool to validate the results.

The RULA assessement method

You must respect the different steps to to analyze the postural risk with the RULA method

Example of the RULA method

A. Shoulder,elbow and wrist analysis

The shoulder score varies between 1 and 6. It’s based on the angle of flexion or extension of the shoulder. As well as the abduction/adduction angle or if the arm is supported.

The shoulder flexion corresponds to the anterior elevation movement of the arm. The extension of the shoulder is defined as a posterior movement of the arm

1a – Adjustments

In addition to your previous scoring, you will need to make some adjustments. If the worker’s shoulder is supported or if the worker is leaning forward, you have to score (-1). If the shoulder is raised, add (+1) and (+1) if the shoulder is abducted.

Dans cet exemple, l’épaule est fléchie d’un peu moins de 32° pour un score de (+2).

The elbow score varies between 1 et 3 . This angle is based on the flexion angle of the elbow.

2a -Adjustments

Select the forearm adjustment if either of the forearm movement is across the midline or outside the body..

In this example, the elbow is flexed for  61° for a score(+1).

The wrist score ranges from 1 à 4. The score is based on the angle of flexion or extension of the wrist.

3a – Adjustments

 

 

Potential adjustment of (+1) if ulnar/radial wrist deviation is observed.

In this example,we observe an ulnar deviation, so we add  (+1) .

Determine the angle corresponding to the rotational movement of the frontal and sagittal planes that is described in the transverse plane.

The angle of pronation of the forearm corresponds to rotation in the direct direction while supination corresponds to rotation in the indirect direction.

The pronation angle is limited to 80°  and to 85° for supination.

In this example, a pronation is observed, so (+1).

Cross the scores obtained in steps 123, 4 to obtain the result corresponding to the first group A including shoulder, elbow, wrist, wrist pronation/supination. 

If the posture is held static for more than 10 minutes or if the action is repeated more than four times per minute, add (+1). If these conditions are not met, no points need to be added.

– If the load is less than 2kg intermittently, add (0),
– If the load is between 2kg and 10kg intermittently, add (+1),
– If the load is between 2kg and 10kg with a static or repetitive posture, add (+2),
-If the load is more than 10kg with repetition or shocks, add (+3);

In this example, the person is carrying a load between 2kg and 10kg intermittently, so we add (+1).

Add the values from steps 5 through 7 to obtain the Group A score including shoulder, elbow, forearm pronation/supination and wrist.

B. Analysis of the neck, trunk and legs

The neck position score varies between 1 and 6. The score is based on the angle of flexion or extension of the neck, as well as any adjustment for axial rotation or lateral bending of the neck.

Neck flexion is the forward movement of the head from a point of neutral neck position. Neck extension is the backward movement of the head from a point of neutral neck position. The neutral position corresponds to the position where the upper body is straight.

9a – Adjustments

Make an adjustment of (+1) if there is lateral bending or rotation of the neck.

In this example, the neck position is between 0 and 10° with a score of (+1).

The trunk position score is between 1 and 6. It is based on the trunk flexion angle, as well as on the axial rotation or lateral bending of the trunk.

Trunk flexion is the rotation of the frontal and transverse planes described in the sagittal plane.

10a – Adjustments

Make an adjustment of (+1) if there is a tilt or rotation of the trunk.

In this example, the trunk position was flexed up to 30°, so we add (+3).

The score for the leg position is between 1 and 2. If the legs and feet are in bipodal support, the score is (+1). If the legs and feet are in monopodal support, the score is (+2).

In this example, the legs are in bipodal support (+1).

Using the values obtained in steps 9 to 11, locate the score in table B corresponding to group B including the neck, trunk and legs.

If the posture is held static for more than 10 minutes or if the action is repeated more than four times per minute, add (+1). If these conditions are not met, no points need to be added.

– If the load is less than 2kg intermittently, add (0),
– If the load is between 2kg and 10kg intermittently, add (+1),
– If the load is between 2kg and 10kg with a static or repetitive posture, add (+2),
-If the load is more than 10kg with repetition or shocks, add (+3);

In this example, the person is carrying a load between 2kg and 10kg intermittently, so we add (+1).

Add the values from 9 through 11 to obtain group B score including neck, trunk and legs.

Cross the values obtained from group A adjusted by muscle activity and effort and load score and the values from group B adjusted by steps 12 to 14 to obtain the representative postural risk score using table C.

Interpretation of results

The RULA score represents the postural risk level of the work task being evaluated. The minimum score is 1, and the maximum score is 7. After referring to table C on the total score for A and B, rate the MSD risk based on the final score.

In this example, the final score of 4 indicates a low risk. A change may be needed to improve work practices to reduce the risk of MSDs.