Revista Ciencias de la Salud
ISSN:1692-7273 | eISSN:2145-4507

Observational Methods for Assessing Ergonomic Risks for Work-Related Musculoskeletal Disorders. A Scoping Review

Métodos observacionales para evaluar los riesgos ergonómicos de los Desórdenes Músculo esqueléticos relacionados con el trabajo: revisión del alcance

Métodos observacionais para avaliar os riscos ergonômicos das Desordens Musculoesqueléticas relacionados com o trabalho: revisão do alcance

Wilhelmus Johannes Andreas Grooten, Elin Johanssons

Observational Methods for Assessing Ergonomic Risks for Work-Related Musculoskeletal Disorders. A Scoping Review

Revista Ciencias de la Salud, vol. 16, 2018

Universidad del Rosario

Wilhelmus Johannes Andreas Grooten *

Karolinska Insitutet, Suecia

Elin Johanssons **

University of Gävle, Suecia

Date received: 10 October 2017

Date accepted: 24 November 2017

Abstract: Introduction: Work-related musculoskeletal disorders (WRMSDS) are one of the most common causes of absence from work. Exposures in the work environment can cause or aggravate the impact of these musculoskeletal disorders and the identification of ergonomic exposures are essential in risk assessment. It is important to assess all three key indicators of these exposures (intensity, frequency and duration) for being able to estimate the risk level for the development of WRMSDS. Aim: This paper aims to give an overview of some of the observational methods that can be used for assessment of ergonomic risks at the workplace. Methods: This study was conducted as a scoping review of the medical and ergonomic literature and official governmental webpages in Sweden, U.S.A. and the Netherlands. Results: In total, 19 different observational methods were identified. We summarize our findings based on the body parts that were studied and what key indicators were assessed: 1) intensity of the work load (posture and force production), 2) frequency of the work load (e.g. repetitive movements), and 3) the duration of the work load (e.g. static work). In an appendix we include a brief presentation of these methods together with the work sheet (if available) and the source reference of the observational method. Conclusion: For ergonomists that perform risk assessments, there is a large number of observational assessment tools available and it is important to understand that different methods can be used simultaneously to be able to estimate the objective risk levels for WRMSDS.

Keywords assessment, ergonomics, musculoskeletal disorders, observational methods, risk.

Resumen: Introducción: los desórdenes músculo-esqueléticos relacionados con el trabajo (DME) son una de las causas más comunes de la ausencia laboral. Las exposiciones en el entorno de trabajo pueden causar o agravar el impacto de estos desórdenes músculo-esqueléticos y la identificación de exposiciones ergonómicas es esencial en la evaluación de riesgos. Es importante evaluar los tres indicadores clave de estas exposiciones (intensidad, frecuencia y duración) para poder estimar el nivel de riesgo para el desarrollo de DME. Objetivo: este artículo tiene como objetivo proporcionar una visión general de algunos de los métodos de observación que se pueden utilizar para evaluar los riesgos ergonómicos en el lugar de trabajo. Métodos: este estudio se realizó como una revisión del alcance de la literatura médica y ergonómica y de las páginas web gubernamentales oficiales en Suecia, EE. UU. Y los Países Bajos. Resultados: en total, se identificaron 19 métodos de observación diferentes. Resumimos nuestros hallazgos en función de las partes del cuerpo que se estudiaron y los indicadores clave evaluados: 1) la intensidad de la carga de trabajo (postura y producción de fuerza), 2) la frecuencia de la carga de trabajo (por ejemplo, movimientos repetitivos) y 3) la duración de la carga de trabajo (por ejemplo, trabajo estático). En un apéndice incluimos una breve presentación de estos métodos junto con la hoja de trabajo (si estaba disponible) y la fuente de referencia del método de observación. Conclusión: para los ergónomos que realizan evaluaciones de riesgo hay una gran cantidad de herramientas de evaluación observacional disponibles y es importante comprender que se pueden usar diferentes métodos simultáneamente para poder estimar los niveles de riesgo objetivo para DME.

Palabras clave: evaluación, ergonomía, desórdenes músculo-esqueléticos, métodos de observación, riesgo.

Resumo: Introdução: as desordens musculoesqueléticas relacionadas com o trabalho (DME) são uma das causas mais comuns da ausência do trabalho. As exposições no entorno de trabalho podem causar ou agravar o impacto destas desordens musculoesqueléticas e a identificação de exposições ergonómicas são essenciais na avaliação de riscos. É importante avaliar os três indicadores chave destas exposições (intensidade, frequência e duração) para poder estimar o nível de risco para o desenvolvimento de DME. Objetivo: este artigo tem como objetivo proporcionar uma visão geral de alguns dos métodos de observação que se podem utilizar para avaliar os riscos ergonômicos no lugar de trabalho. Métodos: este estudo se realizou como uma revisão do alcance da literatura médica e ergonômica e dos sites governamentais oficiais na Suécia, nos Estados Unidos e nos Países Baixos. Resultados: em total, identificaram-se 19 métodos de observação diferentes. Resumimos os nossos achados em função das partes do corpo que se estudaram e os indicadores chave avaliados: 1) a intensidade da carga de trabalho (postura e produção de força), 2) a frequência da carga de trabalho (por exemplo, movimentos repetitivos) e 3) a duração da carga de trabalho (por exemplo, trabalho estático). Em um anexo incluímos uma breve apresentação destes métodos junto à folha de trabalho (se estava disponível) e a fonte de referência do método de observação. Conclusão: para os ergonomistas que realizam avaliações de risco, há uma grande quantidade de ferramentas de avaliação observacional disponíveis e é importante compreender que podem-se usar diferentes métodos simultaneamente para poder estimar os níveis de risco objetivo para DME.

Palavras-chave: qavaliação, ergonomia, desordens musculoesqueléticas, métodos de observação, risco.

Background Ergonomics

Ergonomics involves the interaction between human, technology and organization in the purpose of optimizing health, well-being and performance (1). Deficiencies in the working environment affect the individual, the company and the community. Therefore, well planned ergonomic working environment not only implies health benefits for the individual but also lead to increased quality and productivity gains for the company (2) and for society (3). A specific part within the field of ergonomics is, according to the international ergonomics association (IEA), the compatibility among human anatomical, anthropometric, physiological and biomechanical characteristics and the static and dynamic parameters of physical work (4). Relevant issues are thus working postures, materials handling, repetitive movements, static work, work-related disorders and safety and health (4), aiming to prevent the occurrence of injuries of the musculoskeletal system. These injuries are one of the most common causes of absence from work, leading to individual suffering and enormous costs for society. The most common body-parts that are affected are neck/shoulder and low back (5). Biomechanical exposures in the work environment can cause (6) or aggravate (7) the impact of these injuries, therefore the term work-related musculoskeletal disorders (WRMSDS) is often used to describe these injuries (4).

Prevention of WRMSDS is less costly than rehabilitation and preventive measures aim to detect the potentially harmful ergonomic work situations at an early stage, before WRMSDS occur (2). This process of identifying and classifying the risk levels for WRMSDS is called risk assessment. Risk assessment should be performed systematically by the employer, but there is often a need for an ergonomists with more extensive knowledge about work- environmental conditions. Although risk assessment often is used on an individual level, for example in the investigation if the MSD of a specific worker could be related to his/her specific workplace, risk analyses should analyze the work task rather than focusing on the individual. Moreover, risk assessments should be performed by using methods that are objective and correct, in other words, reliable and valid. It is of great importance that risk assessment is performed before the work task is taken into production, for example, during the planning stage or when reconstructing existing workplaces. By assessing the WRMSD risk in this stage, it is easier to specify the individual demands that are needed to perform the specific task. Ergonomic risk analyses can also be performed when one aims to evaluate the effect of a workplace intervention. Most studies on effects of workplace interventions aim to evaluate the reduction of WRMSDS (8), but this approach is shadowed with a large number of methodological difficulties and it seems to be more feasible to study the effect on ergonomic exposures, rather than the occurrence of injuries.

Using an assembly line as example, workers are exposed to multiple concurrent factors that could lead to WRMSDS, such as the speed and height of the assembly line, the amount of products that are handled, the weight and shape of the products, the weight of the tools used, the duration of the working cycles and the number of pauses. The number of workers on the work site, the number of joints involved, the movement quantity and quality, the ability to alter body positions, psychological stress, time pressure, working hours, time of day, environmental factors (light, temperature, noise, vibrations), and the psychosocial work environment, etc. In a risk assessment of such a complex workplace it is important to structure the exposures into different components based on the pathophysiological mechanisms for WRMSDS. In the best of worlds, a risk assessment should cover all aspects, but often one need to focus on the two or three most important risks in order to find suitable interventions. In a multifactorial environment, one could use one specific assessment method that is perfectly constructed to assess one specific risk in one specific work task over a short time period, or use a general risk assessment method that assesses the total load over a longer time period. So the question is: which approach should be used?

Intensity, Frequency and Duration

When assessing the ergonomic risks, three key indicators of ergonomic exposure should be taken into account: I) the “intensity” of the work load; e.g. awkward posture of the trunk and/or extremities (posture) 3 and force production during lifting, pushing and pulling (due to lifting, pushing and pulling tasks), F) the “frequency” of the work load; e.g. repetitive movements, and D) the “duration” of the work load; e.g. static work, lack of changes in posture (9). Using these categories, many of the common ergonomic risks can be identified: manual handling (I), awkward posture (I/D), repetitive work (F), and static work (D) can be observed.

Table 1 provides examples of how these three key indicators of biomechanical exposure can be clustered against the aforementioned ergonomic risks for WRMSDS. This table also shows that many of the common WRMSDS, due to combinations of risks (6, 7), can be described by more than one key indicator. Moreover, different and similar categories could be expressed in different or similar measures, making it difficult to know which risk or key indicator is observed. For example, by measuring the inclination degree of the back during a lifting task (expressed in degrees and in Newtons) in combination with the time spent in this angle (expressed in percentage of working time or in seconds), one could assess the risk level for WRMSDS for the combination of awkward postures and static work. Previous researches show that the combination of risk factors is an especially important factor to consider in a risk assessment [6]. There is in addition a need for observing concurrent risk factors for WRMSDS.

Table 1
Classification of biomechanical loading into the three key indicators (Intensity, Frequency, and Duration) of the ergonomic risks for WRMSDS, their measures and some of the common WRMSDS associated with these exposures
Classification of biomechanical loading into the
three key indicators (Intensity, Frequency, and Duration) of the ergonomic
risks for WRMSDS, their measures and some of the common WRMSDS associated with
these exposures

Ver notas 4 y 5 .

It should be taken into account that the psychosocial (including organizational) factors, individual and environmental factors are not included in this table; these should be incorporated in the overall judgment of the level of the WRMSD risk at a later phase.

Ergonomic Risk Assessment and Intervention

Ergonomic risk assessment is part of the risk management process that will be included in a systematic analysis of potential hazards to ill-health and accidents. The purpose of making an ergonomic risk assessment is to eliminate work-related health risks by identifying existing or potential risks that may lead to MSDS. When risk factors are identified, interventions to reduce or minimize them must be carried out. Risk assessments can also be useful to evaluate an intervention performed at the workplace.

To successfully implement ergonomic improvements in the work environment, it is important to identify key persons who have the power and obligations to take action at the workplace at an early stage (10). It is of the outmost importance that the risk assessment is well imbedded in the organization and the key persons are employed by the organization. External consultants could be involved in the ergonomic risk assessment, but the intervention should be initiated from within the organization. Moreover, the employees should be included from the beginning. This so called participatory approach, i.e. where the employees are actively involved in the risk assessment and intervention development, has been proved successful in earlier studies (3).

Four Steps in an Ergonomic Risk Analysis

There are four steps involved in an ergonomic risk analysis. First, the physical working situation should map all performed tasks. There are several methods for this, but the hierarchical task analysis (HTA) is a recommended method for this mapping procedure [11]. The next step is to rank the tasks. This can be based on, for example, the time spent on a specific work task, or the severity of the ergonomic problems. This step is followed by an objective assessment of the three key indicators (intensity, frequency and duration) for each work task. Based on the assessment, a decision of the severity of the risk should be taken. A traffic light model —green (no obvious ergonomic problems), yellow/orange (minor/major ergonomic problems) and red (serious ergonomic problems, many workers are at risk of developing WRMSDS)— can be used for this. The fourth and final step is risk management.

In this paper, we focus on the second step, the objective assessment of the ergonomic exposures.

The methods available for the observation of risks can be divided into three categories: questionnaires, observation methods, and technical measurement methods.

  1. Questionnaires: Here, the employee assesses the organization ergonomic risks during work using a questionnaire with pre-defined answers, e.g. the Dutch Musculoskeletal Questionnaire (12). This method is easy to use with large groups of workers and enables comparisons over time and between groups. However in workers with WRMSDS, there could be validity problems since they experience their work with a higher perception in terms of intensity, frequency and duration compared to those with no WRMSDS, thus introducing a serious form of bias, i.e. differential exposure assessment bias (13).

  2. Observational Methods: These methods have to be based on concepts of an external observer (preferably an ergonomist) who fills in a predefined scoring sheet while watching a worker performing his/her work. These methods are more time-consuming but their reliability and validity have been found to be satisfactory (14). Currently, there are many different observational methods for ergonomic risk assessment and no consensus exists on how to choose between them. In 2010, Takala, et al. provided an overview of some of the existing methods (14), but we believe there is a need for an update of this review.

  3. Technical Methods: Lately, there has been a large development of new technical methods for observing postures, movements, and loads. For example, there are smartphones applications that can measure angles over time (15), as well as different types of accelerometers (16, 17, 18) and inclinometers (19, 20), smart clothing (21), and video-based systems (, etc. that could be used for ergonomic risk assessment. These instruments are usually very accurate, but with some disadvantages: they are more expensive than observational methods, they need to be handled by experts and they interfere with the organization’s work.

It is important to choose the most accurate and cost-effective method. We believe that weighing all the pros and cons of these three methods observational methods using pre-defined score sheets seem to be the most useful for ergonomists that work with daily ergonomic risk assessment in work environments.


The aim of this paper is to give an overview of observation methods that can be used in the assessment of ergonomic risks for WRMSDS at the workplace.

Materials and methods


This study was designed as a scoping review of the literature on ergonomic risk assessment. PUBMED, ARBLINE and GOOGLE SCHOLAR databases were searched using combinations of key words such as ‘ergonomic risk’, ‘assessment/measurement/methods’, ‘WRMSDS’, ‘intervention’, together with the three biomechanical exposure categories, intensity, frequency and duration. Moreover, websites from different national institutions (Sweden) and international (the Netherlands, US) were searched as well. The two authors (WG and EJ) searched for methods using a “snowball method”, which means that bibliography of papers also were used to find methods. Special focus was put on papers published after 2008, to add methods that were developed after the systematic review of Takala, et al. (2010) (14).

Included were original papers that present the assessment method of the ergonomic risk exposures at work. Only papers in English, Dutch or Swedish that were available in full text were included. Moreover, only methods that use objective assessment measures were included; that is, an external assessor performs the risk assessment based on a pre-defined scoring sheet without the use of technical equipment.


In total 19 methods were found that met the inclusion criteria, and for each method, the body part that is assessed together with the key indicators are presented in Table 2. In Appendix 1, the methods are described very briefly. In general, those methods had been found easy to use and provided useful information for the ergonomist to communicate the risk to the employer/employee in terms of green, yellow and red, and gave directions for ergonomic interventions.

Six methods assess risks in all body parts simultaneously (OWAS, PATH, PLIBEL, REBA, RULA, and WERA) while the other 13 methods study specific parts. One method (ALLA) focuses on the lower part of the body, only. Concerning intensity, all instruments measure this key indicator and all but one (HAL) assess the workers’ posture. Fourteen of the 19 methods capture the frequency of the work task, while one instrument (KC) only partially assesses frequency, i.e., it asks the examiner with a simple one yes or no question if there were any repetitive movements. Four observation methods (ALLA, LUBA, QEC and RULA) do not include frequency in their risk assessment. Seven methods establishduration (SI, ALLA, HARM, KIM I-II, KIM III, RAMP and WERA) and two methods measure duration only partially (ART, QEC), i.e., if the work task was performed 0-2h, 2-4 h or >4 h/day.

Of the instruments, six assesses all three key indicators: SI, HARM, KIM I-II, KIM III, RAMP and WERA, while one instrument assesses all key issues partly (ART).

Table 2
Observational Methods for the Assessment of Ergonomic WRMSD Risk
Observational Methods for the Assessment of Ergonomic


This study maps a large number of instruments that can be used in the assessment of ergonomic WRMSD risk factors. Table 2 shows an overview of which body parts and key indicators (I, F, D) are assessed by these instruments. All of the instruments assess posture (intensity), but the other two key issues of biomechanical exposure (frequency and duration) were not included in all observational methods. Considering the instruments, only six assess all three key indicators: SI, HARM, KIM I-II and KIM III, RAMP and WERA, and among these, only WERA measures the biomechanical WRMSD risk for all body parts.

For ergonomists that perform risk assessments, there is a large number of observational assessment tools available, it is important to understand that different methods can be used simultaneously in order to estimate the objective WRMSD risk levels.


The authors wish to thank Amanda Hansson for her valuable input on the manuscript.


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Appendix 1. Short description of the observational methods

Agricultural Lower Limb Assessment - ALLA

ALLA is a diverse and segmented ergonomic lower limb assessment tool developed for farm assessing farmers at work. ALLA is especially useful for studying lower limb burdening work [22, 40].

Assessment of Repetitive Task of the upper limbs - ART

ART is suited for tasks that involve actions of the upper limbs that are repeated every few minutes, or even more frequently, and occur for at least 1–2 hours per day or shift. Although ART mainly focuses on upper limbs, neck and back positions are monitored as well. The risk levels for the following factors are assessed: frequency and repetition of movements, power, work postures and influencing factors. If the predetermined risk levels do not fit, the assessment can be placed between two levels. ART can be used in assembly line, production, processing, packaging, packing and sorting work, as well as work involving the regular use of hand tools. ART is not intended for display screen equipment (DSE) assessments. ART has developed an excel sheet for analyzing several tasks that take into account the rotation frequency between different tasks (23).

Cumulative Trauma Disorder - CDT

The instrument was developed for the detection of repetitive strain injuries and includes four main factors that contribute to a sum score (based on a specific equation): the frequency, posture, force and miscellaneous factors (24).

Hand Activity Level

This method intends to assess the MSD risk in the hand and forearm in repetitive work that is performed for at least four hours. The method is based on two variables that are judged by simple observations and estimates of the person performing the work: 1) hand activity level (HAL), that indicates how often the movements are performed (assessed on a VAS scale), and 2) hand force, in which the produced force is estimated with a Borg cr-10 scale. These variables are placed on two axes in a chart with marked areas for red, yellow and green for identification of action and threshold limit values (TLV) (25).


HARM assesses the risk of load-related injuries in the hand, arm, shoulder and neck during work tasks that last for at least one hour while the weight of what is handled is less than 6 kg. The method is intended to be used only for manual and arm-intensive work. It should not be used for assessing computer work. The assessment is conducted on one work task at the time, i.e., if there are several hand-intensive tasks within the work, they are assessed separately. HARM assesses six different areas: time, most active hand, power, work posture, vibration, and other factors. For these areas, different risk points are calculated, which are finally combined, resulting in a risk assessment. Risk levels are graded in green, yellow or red (26). The assessment form is a five-page document, alternatively it is a computerized tool.

Keyserlings Cumulative Trauma Checklist

KC was developed to map the risk factors associated with MSDS in the upper extremities aiming to reduce accidents and inconvenience caused by poor ergonomics at the workplace in a car factory. KC assesses the occurrence of awkward posture, repetitive movements, external forces, vibration, temperature, drafts, tools, and glove use on 18 yes/no questions for both hands. For some factors, duration and frequency are also noted. A total sum score is obtained, the risks are graded into three levels (27).

KIM I (Lifting) and KIM II (Push and Pull)

KIM I is designed for assessment of work tasks that require manual handling during a working day. First, it determines if manual handling primarily involves lifting/holding, holding or carrying loads. This gives a time span. Then the weight of the load is established. The most common job posture is determined as well as various aggravating factors. Finally, a risk point is calculated. Risk levels are graded in green, yellow, orange or red (9).

In a similar way, KIM II is used for assessment of work that involves pushing and pulling. The procedure is similar to KIM I. First, a time point is given, based on the distance that the load is moved (more or less than 5 m). Then, the weight of the load and how it is moved is determined. If the work involves load pushing, the body posture is assessed. Movement speed and body posture are also determined, as well as aggravating factors. Finally, a sum of risk points is calculated. Risk levels are graded in green, yellow, orange or red (9).

KIM III (Repetitive Manual Handling for the Hand-Arm)

KIM III is developed after KIM I and II, it assesses repetitive manual handling for the hand-arm. The latest validated version was published in 2012. The analysis is based on observation of several working cycles. If the cycle time is less than 60 seconds, 5-10 cycles are observed. If the cycle time is longer than 60 seconds, 10-15 cycles are observed. The duration of the activity over a working day, the effort needed, position of hand and arm, work organization, body posture, etc. are determined. Risk levels are graded in green, yellow, orange or red (28).

Loading on the Upper Body Assessment - LUBA

In LUBA, a score is calculated for the posture of each body part. The combined individual score for the neck, shoulders, upper back, lower back, elbows and wrists/hands gives a postural load index (PLI). This PLI score shows how musculoskeletal loading is associated to the worker’s posture. LUBA classifies the risk of musculoskeletal disorders into four action categories (29).

Occupational Repetitive Actions

OCRA is a synthetic index describing risk factors related to repetitive actions at work. The total number of technical actions performed during the shift is divided by the total number of recommended technical actions. The latter is counted from observed actions multiplied by weights given for the following factors: muscle force, posture of the parts of the upper limb, lack of recovery periods, daily duration of the repetitive work, and other additional factors. The OCRA system comprise three assessment tools: 1) The OCRA mini-checklist, which is a simplified version, as a preliminary screening tool is intended for special sectors (e.g. craftwork, small business, agriculture, etc.) in which the work is not organized according to precisely defined rates, times and cycles as it is in industry, 2) the OCRA checklist for initial risk assessment, and 3) the OCRA index for precise and analytical risk assessment (30).

OWAS - the Ovako Working Posture Analysis System

In the OWAS method the four most common work postures for the back, three postures for the arms and seven postures for the legs are identified, together with the load handled (three categories), these 252 options are then classified into four action categories (31). A portable system for coding and analyzing is currently available.

Posture, Activity, Tools, and Handling - PATH

PATH has a work sampling-based approach, it was developed specifically to characterize the ergonomic hazards of heavy highway construction work. PATH is based on the OWAS definitions and uses the same risk levels [32].



PLIBEL is a method for the identification of musculoskeletal stress factors which may have injurious effects. The checklist is designed so that items, ordinarily checked in a workplace assessment of ergonomic hazards, can be listed and linked to symbols of five body regions. The list of items consists of questions concerning awkward work postures, tiresome work movements, poor design of tools or workplace, and stressful environmental or organizational conditions. For a PLIBEL registration there is no duration criterion, excluding rare events or peak loads (33).

Quick Exposure Check - QEC

QEC is suitable for the assessment of many different types of work and work tasks, but each task should be assessed separately. The starting point for the assessment is the worst possible work positions for each body part involved in a task. The observer assesses body posture and body movements while the employee (in cooperation with the observer) estimates time, level of force, visual requirements, vehicle driving, vibrating tools, work load and stress levels. Different combinations of these parameters give points that sum up one body part at the time. Priority levels for possible interventions are proposed for the endpoints (34).

Risk Management Assessment Tool for Manual Handling Proactively - RAMP

RAMP is a newly developed tool to support the assessment and management of risks of musculoskeletal disorder (MSD) in manual handling work. It consists of four modules: 1) a checklist-based “RAMP I” for screening of MSD risks (yes/no), 2) a “RAMP II” which enables a more in depth analysis, 3) a “Results module” for presenting, visualizing and communicating the results, and 4) an “Action module”, for the development of risk reducing measures and systematic risk management. RAMP uses a number of equations in which multiplicative interaction of different ergonomic factors are taken into account. The tool includes two types of assessments, the worst case and the average case, intended to cover both cumulative load and peak load. Both, the initial and the sustained force can be assessed (35).

Rapid Entire Body Assessment Method - REBA

This ergonomic assessment tool uses a systematic process to evaluate the whole body postural MSD and risks associated with work tasks. A single page worksheet is used to evaluate required or selected body posture, forceful exertions, type of movement or action, repetition, and coupling (36).

Source: Hignett, S. and McAtamney, L., Rapid Entire Body Assessment (REBA), Applied Ergonomics, 31, 201-205, 2000.

Rapid Upper Limb Assessment Method - RULA

A single page worksheet is used to evaluate required body posture, force, and repetition. Based on the evaluations, scores are entered for each body region in section A) for the arm and wrist, and section B) for the neck and trunk. After the data for each region is collected and scored, tables on the form are then used to compile the risk factor variables, generating a single score that represents the level of MSD risk. The RULA was designed for easy use without the need for advanced ergonomic knowledge or expensive equipment. By using the RULA worksheet, an evaluator will assign a score for each of the following body regions: upper arm, lower arm, wrist, neck, trunk, and legs. After the data for each region is collected and scored, tables on the form are used to compile the risk factor variables, generating a single score that represents the level of MSD risk (37).

Strain Index - SI

The methodology involves the measurement or estimation of six task variables (intensity of exertion, duration of exertion per cycle, efforts per minute, wrist posture, speed of exertion, and duration of task per day), the assignment of an ordinal rating for each variable according to exposure data, and then the assignment of a multiplier value for each variable. The strain index is the product of these six multipliers (38).

Workplace Ergonomic Risk Assessment - WERA

WERA provides a quick method for screening the working task for assessing the physical risk factors associated with WRMSDS. The WERA tool covers six physical risk factors including posture, repetition, force, vibration, contact stress and task duration and it involves the five main body regions: shoulder, wrist, back, neck and leg. It has a scoring system and contains action levels, which provide a guide to the level of risk and the possible need for action to conduct more detailed assessments (39).


3 It is important to understand that posture alone can cause/aggravate WRMSDS due to the weight of the body segments if they are not supported or due to end range positions of the joints involved.

4 Arthritis/arthrosis, hernia

5 Tendinitis, tendinosis 6 (Semi-)ruptures

Author notes

* Corresponding author:

** Elin Johanssons, PhD

Additional information

To cite this article: Grooten WJA, Johanssons E. Observational Methods for Assessing Ergonomic Risks for Work-Related musculoskeletal disorders. A Scoping Review. Rev Cienc Salud. 2018; 16(especial): p. 8-38. Doi:

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