Industrial ERG

CHAPTER 14 HOW TO CONDUCT AN ERGONOMIC ASSESSMENT AND ERGONOMIC ASSESSMENT TOOLS

LEARNING OBJECTIVE

At the end of this module, you will be able to conduct an ergonomics assessment to include selecting and understanding the use of the applicable evaluation method for the task.

INTRODUCTION

An ergonomics assessment of a job or task leads one through the anticipation, recognition, evaluation, and prioritization and corrective action phases and directs their efforts toward the most effective improvements.

There are simple and complicated methods for the analysis of physical workplace risk factors but can be generalized into four categories:

· Checklist

· Interactive form based

· Observational

· Direct measurement.

No single assessment tool is perfect; however, some assessment tools can be of value to the ergonomist in the field (Marras & Karwowski, 2006). This chapter focuses on observational methods but urges the practitioner to consider using biomechanical modeling software as well as direct reading noise, temperature, and light meters where appropriate.

BACKGROUND

Checklist

· Pros: easy to use, special equipment not required, reminders

· Cons: easily misused, observer bias, not flexible.

Interactive Form Based

· Pros: can be validated, potential respondent anonymity, sample large population quickly

· Cons: responder bias, costly to validate.

Observational

· Pros: easy to use, flexible, can be validated

· Cons: observer bias, observer presence can alter environment.

Direct Measurement

· Pros: can be validated, reliable

· Cons: equipment can be costly, test environment may represent true working conditions, and equipment presence can alter work methods.

PREPARING FOR THE SURVEY

Conducting an observational assessment usually requires the following 13 steps. It is very similar to conducting a job hazard analysis (JHA) or job safety analysis (JSA). The evaluator should become familiar with the technique they intend to employ and practice using the tool before entering the work site.

Step One: Select the Job or Task for Evaluation

· Review medical records or injury logs

· Query workers and supervisors on the following:

· Which tasks are the most awkward or require the most uncomfortable postures?

· Which tasks take the most effort?

· Which tools or pieces of equipment are notoriously hard to work with?

· Have there been changes in processes or procedures?

· Visually assess the jobs or tasks, looking for the ergonomics risk factors that occur for durations longer than 4 h/day and as frequently as three times per week.

Step Two: In Preparation of the Site Visit

The appropriate office should be notified, for example, industrial hygiene, safety, or occupational medicine. It can also be helpful to invite someone from the respective office to accompany them on the site visit. After the visit, these same personnel may be integral to implementing interventions. Select a time that is representative of the task or job they expect to evaluate and plan to spend most of the shift (4–6 h) in the work area.

Step Three: Become Knowledgeable About the Area You Plan to Enter

Obtain permission from the supervisor to enter the area and speak with employees so that everyone understands the purpose, process, and expected outcome. When determining the sample size, generally the rules of industrial hygiene apply and one tries to sample the square root of the number of operators that fall into a similar exposure group. Alternatively, find the most and least experienced operator, conduct the survey and compare results.

Research industries with similar jobs or tasks, looking for best practices or lessons learned. Become familiar with the process by reading standard operating procedures, taking an initial walk through, or discussions with management.

Step Four: Gather the Appropriate Tools for the Assessment

· Measuring tape

· Video or digital camera

· Audio recorder

· Notepad and writing utensil

· All personal protective equipment required for the area and task to be evaluated

· Appropriate checklist or assessment tool

· Light meter

· Force/weight measuring device

· Be sure to calibrate equipment pre- and postsampling. Note that some survey methods such as RULA/REBA and HAL are best employed with the evaluator calibrated.

Step Five: Gather Data

Begin by introducing yourself and explaining the purpose of the site visit. Explain what ergonomics is if the employees and supervisor are not knowledgeable. Explain that the purpose of the survey is to help the workers and this is not an inspection.

Remember, it can be difficult for workers to accept, at first, a suggested change if they have been performing the task the same way for years. Be understanding and make suggestions instead of demands. If an employee is reluctant to change, ask them to try it another way for a few days.

Obtain job or task information, which is primarily accomplished through the interview of the supervisor or designated escort.

· Job name, department, point of contact information

· Shift length

· Production standards

· Rotation schedule

· Number of employees (level of turnover/absenteeism)

· Basic population demographics (age/gender)

· Workplace injuries

· Required personal protective equipment

· Is there seasonal work or fluctuations in production?

· Production rates and quotas

· Is there job rotation?

· Number and frequency of rest breaks

· Process improvement suggestions

· Total exposure time at each subtask or workstation.

Gather user data by interviewing employees.

· Length of time working at job

· Ask the operator to walk them through the tasks.

· Any pain or discomfort associated with the job?

· Number and duration of breaks

· Involvement in health and safety committees

· What are the hardest tasks associated with the job?

· What tools or pieces of equipment are notoriously difficult to work with?

· Previously diagnosed work-related musculoskeletal disorders (WMSDs) or are you under a physicians care for a WMSD?

· Any suggestions for process improvement?

· If they had unlimited funds what would they change?

Do not interfere with the normal process or discuss personnel issues. Avoid leading questions about pain or discomfort. Typically, answers that are more accurate are gathered when workers are not interviewed in groups.

Perform the task analysis by first observing the entire work area and then dividing the major tasks into subtasks. Alternatively, use the information collected from the interviews on where to focus the assessment. Reference assessment tools for specific procedures related to the tool of choice. Each subtask is typically examined for the determination of exposure to ergonomics risk factors. For example:

· Job constraints

· Risk factors (including bending, stretching, twisting, static loads, and maintaining undesirable postures)

· Task associated with the job and frequency

· Measure

· Part and tool weights

· Grip forces and push/pull forces

· Work heights

· Reach distances

· Carrying distances

· Seat heights

· Cart location

· Product dimensions and weights

· What tools are being used? Reference hand tools

· Draw a diagram of the process flow

· Employ the proper survey tool

· Note organization of work surfaces and process flow

· Is there wasted movement or material handling?

Video recordings or digital photographs are an important piece of documentation. Video recording is an opportunity to gather data, document and measure postures, cycle time, and work methods. Video tape also captures the difficulty of a task, is an audio record, can be played back in slow motion and can be used as a training tool. Some video and photographic considerations are as follows:

· Record the process from a variety of angles (front, back, right and left side, overhead)

· Record at least two of five angles

· Record both wide angle and close-up

· If feasible, record at least three cycles of a task

· Carry backup supplies:

· Batteries, film, and memory cards

Upon conclusion of the data gathering:

· Thank everyone for their time and cooperation.

· Inform them of the expected outcome (e.g., report).

· Obtain contact information for follow-up questions.

· Brief appropriate personnel on the findings (in general) and when they can expect a copy of the outcome.

· If time permits, conduct a brainstorming session with employees, OSH or IH personnel, querying their suggestions for task/job improvements.

Step Six: Analyze the Data

Analyze the data to determine if the risk factors are present in a sufficient dose to increase the risk of injury. Incorporate the findings from all the methods employed during the data gathering effort. The assessment tools section contains methods to determine risk prevalence. If possible, brainstorm solutions with others during the report writing stage. An example risk assessment report can be found in the Exercises Appendix section. Report elements can include the following:

· History/background

· Why was 

· the survey requested?

· Injury history.

· Cost figures – actual paid and potential costs.

· Workplace Summary

· Task summary

· Demographics:

· Number of workers

· Age and gender mix

· Reports of discomfort

· Survey findings

· Summarize the methods used to identify the risk factors.

· Summarize risk factor exposure.

· Illustrate with photography or video stills.

· Include the results of the Ergonomic Screening tool, Risk Factor Follow-on checklist; JR/PD or other evaluation method.

· Discuss consequence of current design.

· Recommendations

· Short- and long-term solutions.

· Details of each recommendation and how it will address the identified problems.

· Include diagrams of workstation or work flow suggestions.

· Provide sources for tools/equipment changes.

· Detail administrative controls and training recommendations.

· Cost summary for short- and long-term recommendations.

· Cost/benefit and payback projections.

· Provide assumptions and relate to current workers' compensation, productivity, and/or mission's readiness issues.

Step Seven: Distribute Report

Assist with implementation of recommendations and follow-up.

AMERICAN CONFERENCE OF GOVERNMENTAL INDUSTRIAL HYGIENISTS THRESHOLD LIMIT VALUE (ACGIH TLV) FOR LIFTING

Introduction

The American Conference of Governmental Industrial Hygienists (ACGIH) has developed a threshold limit value (TLV) for lifting. A TLV is defined as workplace lifting conditions under which it is believed nearly all workers may be exposed repeatedly, day after day, without developing work-related lower back and shoulder disorders associated with repetitive lifting tasks.

The ACGIH TLV is a quick and easy tool to assess lifting tasks. The results can also direct the user to job redesign strategies. The information was adapted with permission.

Limitations

When using tables based on psychophysical data, some limitations apply. The tables are based on a realistic, and valid, assessment of what a worker feels he or she can tolerate. It is questionable whether a subject can anticipate how much can be tolerated over the long term without incurring an injury. Therefore, a psychophysical approach may underestimate the actual level of risk.

In addition, the tables assume good coupling between the load and the hands and between the feet and the floor, a two-handed handling, unrestricted posture, less than 30° of twisting, and the task cannot exceed 8 h/day or 360 lifts/h.

Applying the TLV

The tool consists of three charts; the chart used determines the TLV. The charts are a function of lifting duration (less than or greater than 2 h a day) and lifting frequency (how many average lifts). Then based on one of the four vertical zones (refer to  Figure 14.1 ) and one of the three horizontal zones, a TLV for weight is given. In some cases, the chart indicates that there is no known safe limit for repetitive lifting under those conditions.

1. Step one: Determine the duration of the lifting exposure. Is the cumulative dose more than or less than 2 h/day?

2. Step two: Determine the frequency of lifting. How many lifts are performed in an hour or in a minute?

3. Step three: Locate the corresponding chart. Chart one is for infrequent lifting ( Table 14.1 ), chart two for moderate lifting ( Table 14.2 ), chart three for highly repetitive lifting ( Table 14.3 ).

Typically, the average lifting scenario is chosen. For example, a worker unloads five delivery trucks a day; each truck has approximately 50 packages. It takes the worker 1 h to unload each truck. The duration of the exposure is . The frequency of lifting is . .

For this scenario, 5 h/day, 50 lifts/h, chart 3 is chosen.

Table 14.1  TLV for low frequency lifting tasks

colspan="4">≤2 h/day with ≤60 lifts/h or >2 h/day with ≤12 lift/h
rowspan="2">Vertical Zone	Horizontal Zonea
Close<30 cm (12 in.)	Intermediate30–60 cm (12–24 in.)	Extendedb>60–80 cm (24–32 in.)
Reach limitc or 30 cm (12 in.) above shoulder to 8 cm (3 in.) below shoulder	16 kg (35 lb)	7 kg (15 lb)	No safe limit for repetitive liftingd
Knuckle heighte to below shoulder	32 kg (71 lb)	16 kg (35 lb)	9 kg (20 lb)
Middle shin to knuckle heighte	18 kg (40 lb)	14 kg (30 lb)	7 kg (15 lb)
Floor to middle shin height	14 kg (31 lb)	No known safe limit for repetitive liftingd	No known safe limit for repetitive liftingd

Source: From ACGIH®, 2013 TLVs® and BEIs® Book. Copyright 2013. Reprinted with permission.

a Distance from midpoint between inner ankle bones and the load.

b Lifting tasks should not be started at a horizontal reach distance more than 80 cm (32 in.) to the midpoint between the inner ankle bones ( Figure 14.1 ).

c Routine lifting tasks should not be conducted from starting heights greater than 30 cm (12 in.) above the shoulder or more than 180 cm above floor level ( Figure 14.1 ).

d Routine lifting tasks should not be performed for shaded table entries marked “No known safe limit for repetitive lifting.” While the available evidence does not permit identification of safe weight limits in the shaded regions, professional judgment may be used to determine if infrequent lifts of light weights may be safe.

e Anatomical landmark for knuckle height assumes the worker is standing erect with arms hanging at the sides.

Table 14.2  TLV for moderate frequency lifting tasks

colspan="4">≤2 h/day with >60 and ≤360 lifts/h Or >2 h/day with >12 and ≤30 lifts/h
rowspan="2">Vertical Zone	Horizontal Zonea
Close <30 cm (12 in.)	Intermediate 30–60 cm (12–24 in.)	Extendedb >60–80 cm (24–32 in.)
Reach limitc or 30 cm (12 in.) above shoulder to 8 cm (3 in.) below shoulder	14 kg (31 lb)	5 kg (11 lb)	No safe limit for repetitive liftingd
Knuckle heighte to below shoulder	27 kg (60 lb)	14 kg (31 lb)	7 kg (15 lb)
Middle shin to knuckle heighte	16 kg (35 lb)	11 kg (24 lb)	5 kg (11 lb)
Floor to middle shin height	9 kg (20 lb)	No known safe limit for repetitive liftingd	No known safe limit for repetitive liftingd

Source: From ACGIH®, 2013 TLVs® and BEIs® Book. Copyright 2013. Reprinted with permission.

a Distance from midpoint between inner ankle bones and the load.

b Lifting tasks should not be started at a horizontal reach distance more than 80 cm (32 in.) to the midpoint between the inner ankle bones ( Figure 14.1 ).

c Routine lifting tasks should not be conducted from starting heights greater than 30 cm (12 in.) above the shoulder or more than 180 cm above floor level ( Figure 14.1 ).

d Routine lifting tasks should not be performed for shaded table entries marked “No known safe limit for repetitive lifting.” While the available evidence does not permit identification of safe weight limits in the shaded regions, professional judgment may be used to determine if infrequent lifts of light weights may be safe.

e Anatomical landmark for knuckle height assumes the worker is standing erect with arms hanging at the sides.

Table 14.3  TLV for high frequency and long duration lifting tasks

colspan="4">>2 h/day with >30 and ≤360 lifts/h
rowspan="2">Vertical Zone	Horizontal Zonea
Close <30 cm (12 in.)	Intermediate 30–60 cm (12–24 in.)	Extendedb >60–80 cm (24–32 in.)
Reach limitc or 30 cm (12 in.) above shoulder to 8 cm (3 in.) below shoulder	11 kg (24 lb)	No known safe limit for repetitive liftingd	No safe limit for repetitive liftingd
Knuckle heighte to below shoulder	14 kg (31 lb)	9 kg (21 lb)	5 kg (11 lb)
Middle shin to knuckle heighte	9 kg (20 lb)	7 kg (15 lb)	2 kg (4 lb)
Floor to middle shin height	No known safe limit for repetitive liftingd	No known safe limit for repetitive liftingd	No known safe limit for repetitive liftingd

Source: From ACGIH®, 2013 TLVs® and BEIs® Book. Copyright 2013. Reprinted with permission. Source: Reproduced with permission from the American Conference of Governmental Industrial Hygienist Threshold Limit Value/Biological Exposure Indices Guide Book 2013.

a Distance from midpoint between inner ankle bones and the load.

b Lifting tasks should not be started at a horizontal reach distance more than 80 cm (32 in.) to the midpoint between the inner ankle bones ( Figure 14.1 ).

c Routine lifting tasks should not be conducted from starting heights greater than 30 cm (12 in.) above the shoulder or more than 180 cm above floor level ( Figure 14.1 ).

d Routine lifting tasks should not be performed for shaded table entries marked “No known safe limit for repetitive lifting.” While the available evidence does not permit identification of safe weight limits in the shaded regions, professional judgment may be used to determine if infrequent lifts of light weights may be safe.

e Anatomical landmark for knuckle height assumes the worker is standing erect with arms hanging at the sides.

4. Step four: Determine the horizontal zone at the start of the lift, reference  Figure 14.1 .

5. Step five: Determine the vertical zone at the start of the lift, reference  Figure 14.1 .

6. Step six: Locate the corresponding weight limit, this is the unadjusted TLV.

7. Step seven: Use your professional judgment to adjust (reduce) the TLV if any of the following conditions exist:

· High-frequency lifting >360 lifts/h (6 lifts/min)

· Lifting performed for longer than 8 h/day

· High asymmetry: lifting more than 30°

· One-handed lifting

· Constrained lower body posture, such as lifting while seated or kneeling

· Poor hand coupling: lack of handles, cutouts or other grasping points

· Unstable foot (e.g., inability to support the body with both feet while standing)

· During, or immediately after exposure to whole-body vibration at, or above the TLV for whole-body vibration.

8. Step eight: If the load is placed at the destination in a controlled manner, repeat steps four through seven for those parameters.

9. Step nine: If the recommended weight limit is exceeded, use the TLV tables (changing object location, handling frequency, or duration) to bring the task into a less hazardous environment. Refer the Manual Material Handling module and the Administrative Controls module for possible solutions.

Figure 14.1  Vertical and horizontal lifting zone (Adapted with permission from Ergonomic Image Gallery)

LIBERTY MUTUAL MANUAL MATERIALS HANDLING GUIDELINES

Introduction

The complete Liberty Mutual Manual Materials Handling Guidelines manual is found at ( https://libertymmhtables.libertymutual.com/CM_LMTablesWeb/taskSelection.do?action=initTaskSelection ).

The goals of the tool are as follows:

· Providing an objective risk assessment of manual handling tasks such as lift, lower, push, pull, and carrying tasks

· Controlling costs associated with manual handling tasks.

Background

· Tables based on psychophysical research by Dr Snook and Dr Ciriello with the LM Research Institute for Safety (Snook & Ciriello, 1991)

· In the Liberty Mutual studies, the worker is given control of the weight of the object being handled and all other variables frequency, size, height, distance, etc. are controlled by the researcher. The worker monitors his/her feelings of exertion or fatigue and adjusts the weight of the object accordingly.

· The psychophysical methodology included measurements of O2 consumption, heart rate, and anthropometrics.

Theory Behind Tables

· Designing manual material handling for greater than 75% of the female work population will offer protection from manual handling injuries.

· Tasks that have “population percentages of 10%” (only capable by less than 10% of the population) will most likely lead to injury.

· The tables can be used to perform “what-if scenarios.”

Benefits of the Tables

· Simple to use.

· Recommended for moderate frequency tasks. Physiological models recommended for high-frequency tasks and biomechanical models for lifting tasks with lower frequency and heavier weights.

· Provides male and female population percentages able to perform the job without becoming unusually tired, weakened, overheated, or out of breath. Encompasses lifting, lowering, pushing, pulling, and carrying tasks.

Limitations to the Tables

There are a number of other considerations besides population percentage that the tables do not address that must be considered in task assessment including the following:

· Injuries

· Frequent bending

· Frequent twisting

· Frequent reaching(horizontal or increasing hand distance away from body and vertical hand distance above shoulder height)

· One-handed lifts

· Note: The containers used by subjects in the lab had handholds.

· Catching or throwing items.

Applying the Tables

Example 1

As mentioned, the tables are relatively self-explanatory. Given the following scenario, this example will illustrate the steps required to determine the population percentage for the task:

You observe the following task in a manufacturing plant lowering air compressor parts. The task has the following characteristics:

· Object weight: 45 lb

· Hand distance: 10 in. from body

· Initial hand height: 24 in. off the walking surface

· Ending hand height: 6 in. off the walking surface

· Therefore, the lowering distance is (24–6 in.) = 18 in.

· Lifting frequency: Every 30 s

1. Step one: Find the correct male and female table that corresponds to the following:

a. Type of task (lifting, lowering, pushing, pulling, etc.)

b. Beginning/ending position of the hands and location

· OR

Type of force applied (initial or sustained).

Given this information, select the appropriate table from the Table of Contents page:

Therefore, the correct table is “4M and 4F.”

Figure 14.2  Liberty mutual table guide for different populations and lifting heights (Adapted from  https://libertymmhtables.libertymutual.com/CM_LMTablesWeb/taskSelection.do?action=initTaskSelection , Copyright 2005 Liberty Mutual Insurance, used with permission)

Figure 14.3  Liberty mutual table guide for step two male population percentages (Adapted from  https://libertymmhtables.libertymutual.com/CM_LMTablesWeb/taskSelection.do?action=initTaskSelection )

Figure 14.4  Liberty mutual table guide for step three female population percentages Step four Interpret results (Adapted from  https://libertymmhtables.libertymutual.com/CM_LMTablesWeb/taskSelection.do?action=initTaskSelection , Copyright 2005 Liberty Mutual Insurance, used with permission)

2. Step two: Find the appropriate male population percentages by entering the information into the websites calculator ( Figures 14.2  and  14.3 ):

3. Step three: Find the appropriate female population percentage by entering the information into the website calculator ( Figure 14.4 ).

The population percentage for this task is determined to be acceptable within the range of less than 10–57%.

As a general rule of thumb, designing manual tasks for greater than 75% of the female work population will offer the best protection from manual handling injuries. Studies have shown that two-thirds of low back claims from low percentage tasks (tasks capable of being performed by a small percentage of the population) can be prevented if the tasks are designed to accommodate at least 75% of the female work population (Snook et al., 1978). However, whenever manual handling and deep bending are combined, this significantly increases the risk of manual handling injuries. Therefore, additional protection for workers is recommended. When workers must bend noticeably during any lifting or lowering task, designing these manual tasks for greater than 90% of the female work population will offer a more appropriate level of protection from manual handling injuries.

Finally, for certain jobs and industries, it is very difficult to design jobs that can be performed by 75% or greater of the female work population. These tables are very often used to perform what-if scenarios of various ergonomic interventions to help determine the most cost-effective and practical solution that offers the highest degree of control. There is no right answer or wrong solution. Whatever solution offers the most practical, cost-effective and highest degree of control possible is a good result.

PHYSICAL RISK FACTOR CHECKLIST

Introduction

The Physical Risk Factor Checklist is a tool used to identify and evaluate ergonomics stressors. The checklist was adapted from the Washington State Labor and Industries hazard and caution zone checklists and is used by the US Navy and can be found in OPNAVINST 5100.23 (series) Chapter 23 Ergonomics Program.

The Physical Risk Factor Checklist ( Figure 14.5 ) examines individual body areas for risk based on posture, force, duration, and frequency.

Figure 14.5  Physical risk factor checklist that can be found in  Appendix C  (Adapted from OPNAVINST 5100.23 (G) Chapter 23, Appendix A)

Applying the Checklist

Start by identifying the ergonomics stressors, either through direct observation, or watching a videotape play back. Watching a video in slow motion enables greater accuracy.

This checklist is used for typical work activities that are a regular and foreseeable part of the job, occurring more than 1 day/week, and more frequently than 1 week/year.

The Physical Risk Factor Ergonomics Checklist is a tool used to identify physical stressors in the workplace. For each category determine whether the physical risk factors rate as a “caution” or “hazard” by placing a check (.) in the appropriate box. Make a notation if a category is not applicable.

If a hazard exists, it must be reduced below the hazard level or to the degree technologically and economically feasible. Ensure workers exposed to ergonomics stressors at or above the “hazard” level have received general ergonomics training and provide a refresher of the ergonomics physical and contributing risk factors.

If the task rates a “caution,” reevaluate at least yearly since changes in the work environment may create new ergonomics stressors.

Reduce to the lowest level feasible significant contributing physical risk factors and consider contributing personal risk factors in evaluation. Contributing risk factors contribute to but do not cause WMSDs. Physical contributing risk factors may include temperature extremes, inadequate recovery time, and stress on the job. Personal contributing risk factors may include but are not limited to age, pregnancy, obesity, thyroid disorder, arthritis, diabetes, or preexisting injuries such as wrist/knee/ankle strain or fracture, back strain, trigger finger, and carpal tunnel syndrome. Professional judgment should be used in instances where personal or physical contributing factors are present. The risk of developing a WMSD increases when ergonomics risk factors occur in combination. See the complete physical risk factor checklist in  Appendix C  of this manual.

AMERICAN CONFERENCE OF GOVERNMENTAL INDUSTRIAL HYGIENISTS THRESHOLD LIMIT VALUE FOR HAND ACTIVITY LEVEL (ACGIH HAL)

Introduction

ACGIH has developed an action limit (AL) for hand-arm activity levels (HAL) and a TLV. The TLV and AL are based on the peak hand force and the hand/arm activity level for a given task. Peak hand force can be measured quantitatively (i.e., strain gauge, biomechanical analysis), or qualitatively (observer or worker ratings, strength based on anthropometric percentiles). HAL can also be measured quantitatively (i.e., calculations based on the frequency of exertions and the work/recovery ratio), or qualitatively (worker or observer ratings). This chapter focuses on qualitatively. This material was adapted with permission.

Limitations and Benefits

The ACHIG TLV for HAL is designed to analyze monotasks. HAL is most valuable for jobs with repeatable steps that involve performing a similar set of motions or exertion repeatedly, for four or more hours per day. A few examples are working on an assembly line and using a keyboard and mouse.

Applying the Survey

HAL is a combination of average HAL and peak hand force (Pf) that indicate (from available data) when hand, wrist, and/or forearm WMSDs are as follows:

· Possible in many people

· Possible in some people

· Unlikely in most people.

Step one: The first step is observing at least three complete task cycles. A useful tool for collecting data can be found in  Table 14.4 . Disregard irregular or spurious actions and then determine the HAL using the observer ratings on a scale of 1–10 with anchors detailed in  Figure 14.6 . The scale is a modified Borg Scale. Compare the task with known examples as necessary. The rating is an average for the entire work cycle. Rate what you see. Ratings can then be adjusted for other factors, for example, increased or decreased production rates, and force.

Table 14.4  HAL and NPF Data Collection Sheet

colspan="3">Date:
Job:
	Left	Right
Hand-arm activity level (HAL) Refer to scale
Normalized peak force (NPF) Refer to scale
Ratio = NPF/(10 − HAL)
Determine results TLV = 0.78 AL = >0.56	>TLV  AL to TLV  <AL	>TLV  AL to TLV  <AL

Figure 14.6  HAL-observed rating scale (From ACGIH®, 2013 TLVs® and BEIs® Book. Copyright 2013. Reprinted with permission)

A data collection sheet can be used as a guide when gathering data.

Step two: The second step is to determine normalized peak hand forces. Disregard irregular or spurious actions and then estimate the normalized peak force (NPF) using observer ratings on a scale of 1–10 with anchors detailed in  Table 14.5 . Compare the task with known examples as necessary. The rating is an average for the entire work cycle. Rate what you see. Ratings can then be adjusted for other factors, for example, increased or decreased production rates, force.

Table 14.5  Estimation of Normalized Peak Force for Hand Activity Level

rowspan="2">% MVC	Subjective Scale	Moore–Garg Observer Scale (Alternative Method)
Score	Verbal Anchor
0	0	Nothing at all
5	0.5	Extremely weak (just noticeable)	Barely noticeable or relaxed effort
10	1	Very weak
20	2	Weak (light)	Noticeable or defined effort
30	3	Moderate
40	4		Obvious effort but unchanged facial expressions
50	5	Strong (heavy)
60	6		rowspan="2">Substantial effort with changed facial expression
70	7	Very strong
80	8
90	9		Uses shoulders or trunk for forces
100	10	Extremely strong (almost maximum)

Source: Adapted from Borg's perceived exertion and pain scales (Borg, 1998).

Notes: The TLVs are guidance on the levels of exposure and conditions under which it is believed workers may be repeatedly exposed day after day, without adverse health effects. TLVs are not single numbers, but rather a combination of measured parameters and/or its effects on workers. Wide variations in individual susceptibility, exposure of an individual at, or even below, the TLV may result in annoyance, aggravation of a preexisting condition, or occasionally even physiological damage.

1. Step three: The third step is to locate the combination or intersection of HAL and NPF on the TLV graph. For example, an NPF of 4 and a HAL of 6 is considered an unacceptable exposure. See  Figure 14.7 .

· Posture

· Sustained, nonneutral positions such as wrist flexion

· Extension, deviation or forearm rotation

· Contact stress

· Vibration

· Low temperature (<20 °C)

· Extended work shifts

· Preexisting injury.

Figure 14.7  Normalized peak hand force and hand activity level threshold limit value determination (From ACGIH®, 2013 TLVs® and BEIs® Book. Copyright 2013. Reprinted with permission)

RAPID UPPER LIMB ASSESSMENT (RULA)

Introduction

The Rapid Upper Limb Assessment (RULA) method has been developed by Dr Lynn McAtamney and Professor E. Nigel Corlett, ergonomists from the University of Nottingham in England (Dr McAtamney is now at Telstra, Australia). RULA is a postural targeting method for estimating the risks of work-related upper limb disorders. A RULA assessment gives a quick and systematic assessment of the postural risks to a worker. The analysis can be conducted before and after an intervention to demonstrate that the intervention has worked to lower the risk of injury.

The full RULA tables are shown in  Appendix C – Survey Tools. Below each step is shown an illustration demonstrating how to score that step.

Applying the Assessment Tool

The following are the steps of a RULA analysis:

1. Step one: Locate upper arm position and score the position of the upper arm ( Figure 14.8 ).

2. Step two: Locate the lower arm position and score the position of the lower arm ( Figure 14.8 ).

3. Step three: Locate wrist position and score the wrist position ( Figure 14.9 ).

4. Step four: Determine wrist twist, score accordingly ( Figure 14.10 ).

5. Next we need to determine the score from Table A ( Figure 14.9 ). This value is then fed into Step five.

6. Steps 6–8 are performed using data from the previous steps as shown in  Figure 14.11 .

7. Step 9: Locate and score the neck position and enter in the box ( Figure 14.12 ).

8. Step 10: Locate the trunk position and then scoring the position in the box ( Figure 14.12 ).

9. Step 11: Determine the score for supporting the legs and scoring ( Figure 14.12 ).

10. We next need to determine the score from Table B to be used in Step 12 (  Figure 14.13 ).

11. Steps 13–15 are performed to determine the neck, trunk, and leg scores ( Figure 14.14 ).

Figure 14.8  Upper and lower arms score (Created by Dr Ostrom)

Figure 14.9  Wrist score

Figure 14.10  Find the accurate value by finding the intersection of steps one through four on the matrix which is Table A

Figure 14.11  RULA force and muscle use values (Original graphic by Dr Ostrom)

Figure 14.12  RULA neck, torso, and leg score

Figure 14.13  RULA Table B trunk posture score

Figure 14.14  Leg, posture, and muscle activity calculation

The final score is determined from RULA Table C ( Figure 14.15 ).

Figure 14.15  Final RULA score

The RULA action levels give you the urgency about the need to change how a person is working as a function of the degree of injury risk.

1. Action level 1 – RULA score 1–2 means that the person is working in the best posture with no risk of injury from their work posture.

1. Action level 2 – RULA score 3–4 means that the person is working in a posture that could present some risk of injury from their work posture, and this score most likely is the result of one part of the body being in a deviated and awkward position, so this should be investigated and corrected.

2. Action level 3 – RULA score 5–6 means that the person is working in a poor posture with a risk of injury from their work posture, and the reasons for this need to be investigated and changed in the near future to prevent an injury.

3. Action level 4 – RULA score 7–8 means that the person is working in the worst posture with an immediate risk of injury from their work posture, and the reasons for this need to be investigated and changed immediately to prevent an injury.

RAPID ENTIRE BODY ASSESSMENT (REBA)

Introduction

The Rapid Entire Body Assessment (REBA) method was developed by Dr Sue Hignett andDr Lynn McAtamney, ergonomists from University of Nottingham in England (Dr McAtamney is now at Telstra, Australia). REBA is a postural targeting method for estimating the risks of work-related entire body disorders. A REBA assessment gives a quick and systematic assessment of the complete body postural risks to a worker. The analysis can be conducted before and after an intervention to demonstrate that the intervention has worked to lower the risk of injury.

Appendix C contains the REBA tables.

The following are the steps of a REBA analysis. Below each step is shown an illustration demonstrating how to score that step:

1. Step 1 is to determine the neck position and how to score (Figure 14.16).

2. Step 2 is to determine trunk position and how to score (Figure 14.16).

3. Step 3 is to determine score for the legs and enter (Figure 14.16).

4. Step 4 is to determine the posture score. To perform this you find the score on Table A using the values from Steps 1–3 above (Figure 14.17).

5. Steps 5 and 6 determine which row in Table C the final score will be located (Figure 14.18).

6. Step 7 determines the score for the upper arm posture and is placed in the box.

7. Step 8 determines the scoring for the lower arm (Figure 14.19).

8. Step 9 determines the score for the wrist (Figure 14.20).

9. Step 10 determines the posture score from Table B as shown in Figure 14.21.

10. Steps 11 and 12 determine which column in Table C the score is found.

11. Step 13 determines the activity score.

12. Step 14, final step, combines the scores from Steps 6, 12, and 13. This is the REBA Score. Figure 14.22.

Figure 14.16  REBA neck, trunk, and leg score (Original graphic by Dr Ostrom)

Figure 14.17  REBA Table A posture scoring

Figure 14.18  REBA posture and force score will be fed into REBA Table C at the end of the process (Original graphic by Dr Ostrom)

Figure 14.19  REBA upper and lower arm score

Figure 14.20  Reba posture scoring Table A for neck, trunk, and legs

Figure 14.21  REBA posture scoring that will feed into REBA Table C at the end of the process

Figure 14.22  REBA Table C determines the final action-level score that is used to assess risk in the workplace

Table 14.6 shows the Action Levels based on the REBA score.

Table 14.6  REBA Action-Level Scores and Action Required

Action Level	REBA Score	Risk Level	Action Required
0	1	Negligible	None
1	2–3	Low	Maybe necessary
2	4–7	Medium	Necessary
3	8–10	High	Necessary soon
4	11–15	Very high	Necessary now

MIL-STD-1472F, MILITARY STANDARD, HUMAN ENGINEERING, DESIGN CRITERIA FOR MILITARY

Systems, Equipment, and Facilities (Section 5.9.11.3 Weight)

Introduction

The Department of Defense Design Criteria Standard for Human Engineering 1472F (Defense, 1999) (MIL-STD 1472G) is intended to present human engineering design criteria to achieve mission success.

Limitations

A limitation of the MIL-STD 1472 is its primary purpose is in the design and development of new systems and is intended to be used for infrequent lifting.

Applying the Standard

1. Step one: Observe the lifting task to obtain lifting frequency (lifts/min), cumulative lifting duration, maximum and average weight handled, average object size, lifting heights (ground to 3 ft or ground to 5 ft) and user population (male, female, or mixed). Where it is not possible to define the height to where the object is lifted, the shoulder height value can be used (5 ft).

1. Step two: The weight limits in Table 14.7, conditions A (lifting to 5 ft) and B (lifting to 3 ft), can be used as the maximum values in determining the weight of items lifted by one person with two hands. The weight limits can be double if two people are performing the lift, with two hands and the load is evenly distributed.

· If one male is lifting, use the male-only population column.

· If one female is lifting, use the female and male population column.

· If two (or more) males are lifting, use the male-only population column.

· If two females (females and males) are lifting, use the male and female column.

· If the load is not evenly distributed, the weight limit applies to the heavier point.

· Where three or more persons are lifting simultaneously, not more than 75% of the one-person value may be added for each additional lifter, provided that the object is sufficiently large that the lifters do not interfere.

2. Table 14.7  Weight Limit Table, Values for Two Lifters in Parenthesis

Handling Function	Male and Female (lb)	Male Only (lb)
A. Lift an object from the floor and place on a surface not greater than 5 ft above the floor	37 (74)	56 (112)
B. Lift an object from the floor and place on a surface not greater than 3 ft above the floor	44 (88)	87 (174)

3. Source: Adapted from MIL-STD 1472G.

4. For example:

· One male can safely lift 56 lb from the floor to 5 ft.

· One male can safely lift 87 lb from the floor to 3 ft.

· One female can safely lift 37 lb from the floor to 5 ft.

· One female can safely lift 44 lb from the floor to 3 ft.

· Two males can safely lift (56 × 2) 112 lb from the floor to 5 ft.

· Two females (or a male and female) can safely lift (37 × 2) 74 lb from the floor to 5 ft.

· Three lifters (mixed population) can safely lift 92.5 lb from the floor to 5 ft.

Calculation as follows:

The one-person value plus 75% of the one-person value for each additional lifter

Step three: adjust the maximum weight limit if the following conditions occur:

Lifting frequency: If the frequency of the lift exceeds 1 lift in 5 min or 20 lifts in 8 h, the permissible weight limit is reduced by  where LF is the lifting frequency in lifts for minute.

1. In the previous example, three people can safely lift 92.5 lb. If the lifting frequency is 6 lifts/min, then the maximum permissible weight is reduced by 50%.

Calculation as follows:

Load size: The maximum permissible weight limits in  Table 14.7  apply to an object of uniform mass that does not exceed . This places the hand at half the depth or 6 in. from the body. If the depth exceeds 24 in., the permissible weight is reduced by 33%. If the depth exceeds 36 in., the permissible weight is reduced by 50% and by 66% if the depth exceeds 48 in.

Obstacles: If an object limits a lifter's approach, the maximum permissible limit is reduced by 33%.

NATIONAL INSTITUTE FOR OCCUPATIONAL SAFETY AND HEALTH WORK PRACTICES LIFTING GUIDE

Introduction

In 1991, the National Institute for Occupational Safety and Health issued a revised work practices lifting guide (WPLG) for the design and evaluation of manual lifting tasks. The 1991 equation uses six factors that have been determined to influence lifting difficulty, combining the factors into one equation. Using the guide involves calculating values for the six factors in the equation for a particular lifting and lowering task, thereby generating a recommended weight limit (RWL) and lifting index (LI) for the task.

The equation incorporates a term called the lifting index, which is defined as a relative estimate of the level of physical stress associated with a particular manual lifting task. The estimate of the level of physical stress is defined by the relationship of the weight of the load lifted divided by the recommended weight limit.

· An LI below 1 indicates the task is safe for most healthy workers.

· An LI between 1 and 3 indicates that the object weight exceeded the RWL and should be addressed using either administrative or engineering controls. The task is safe for some but not all workers.

· An LI level greater than three indicates that the lifted weight exceeds the capacity to safely lift for most of the population, is likely to cause injury, and should be modified by implementation of engineering controls immediately.

Limitation

A limitation of the NIOSH WPLG is it assumes one person is performing a lift and does not take the stature of the individual into account. In addition, the RWL is within the strength capabilities of 75% of all women and 99% of all men.

NIOSH WPLG Assumptions

Application of the NIOSH WPLG assumes the following:

· Lifting task is two-handed and smooth.

· The hands are at the same height or level, and the load is evenly distributed between both hands.

· Manual handling activities other than lifting are minimal and do not require significant energy expenditure.

· Temperatures (66–79 °F) and humidity (35–50%) are within an acceptable range.

· One-handed lifts, lifting while seated or kneeling, lifting in a constrained or restricted work space, lifting unstable loads, wheelbarrows and shovels are not tasks designed to be covered by the WPLG.

· The shoe sole to floor surface coupling should provide for firm footing.

· Lifting and lowering assumes the same level of risk for low back injuries.

· Lifting outside of the ranges may increase the risk of injury.

Using the WPLG in situations that do not conform to these ideal assumptions will typically underestimate the hazard. The computed values of the lifting index are used by the OSH professional as a guide to estimate risk. The numbers by themselves do not identify a hazardous activity. The employer's incidence of injuries and lack of programs for training, work practice controls, and engineering controls related to lifting are elements used to determine the seriousness of the hazard.

Applying the Guide

The relevant task variables must be carefully measured and clearly recorded in a concise format. The Job Analysis Worksheet for either a single-task analysis or a multitask analysis provides a simple form for recording the task variables and the data needed to calculate the RWL and the LI values. The data needed for each task include the following:

The lifting equation for calculating the RWL is based on a multiplicative model of the six variables ( Table 14.8 ).

where if a formula results in a number less than one, use one. None of the values can be negative and therefore where appropriate the absolute value is used.

Table 14.8  NIOSH Work Practices Lifting Formula

Multiplier	Definition	Formula	Notes
LC	Load constant	51 lb
HM	Horizontal multiplier	10/H
VM	Vertical multiplier
DM	Distance multiplier	where D is
AM	Asymmetric multiplier		A is between 0° and 130°
FM	Frequency multiplier	From look-up table
CM	Coupling multiplier	From look-up table

Anatomy of a Lift

Explained in  Figure 14.23

1. Weight of the object lifted – Determine the load weight (L) of the object (if necessary, use a scale). If the weight of the load varies from lift to lift, record the average and maximum weights and calculate an LI for each.

2. Horizontal location of the hands with respect to the midpoint between the ankles (H) – The horizontal location of the hands at both the start (origin) and end (destination) of the lift is measured. The horizontal location is measured as the distance from the midpoint between the employee's ankles to a point projected on the floor directly below the midpoint of the hands grasping the object (the middle knuckle can be used to define the midpoint). The horizontal distance should be measured when the object is lifted (when the object leaves the surface).

3. Vertical location of the hands (V) – The vertical location is measured from the floor to the vertical midpoint between the two hands.

4. Travel distance (D) – The total vertical travel distance of the load during the lift is determined by subtracting the vertical location of the hands at the start of the lift from the vertical location of the hands at the end of the lift. This number is always positive.

5. Angle of asymmetry (A) – Determine the angle of asymmetry at the origin and destination of the lift. If the worker's hands are directly in front of the body and the worker is not twisting the angle would be 0. If the worker is twisting to where the hands are over the hips, the angle would be closer to 90°. See  Figure 14.24 .

6. Lifting frequency – First determine the total lifting time or duration of lifting and then use the frequency table to find the multiplier based on lifts per minute and the position of the hands,  Table 14.8 .

7. Coupling type – Classify the hand-to-container coupling based on  Table 14.9 .

8. Frequency of lift – Determine the average lifting frequency rate (F), in lifts per minute, periodically throughout the work session (average over at least an 15-min period). If the lifting frequency varies from session to session by more than 2 lifts/min, each work session should be analyzed as a separate task. The duration category, however, must be based on the overall work pattern of the entire work shift. The value is determined via a look-up table as seen in  Table 14.10 .

Figure 14.23  Anatomy of a lift

Figure 14.24  Asymmetry multiplier (Adapted from Ergonomics Plus Sweetster IN)

Table 14.9  Coupling Look-Up Multiplier Table

Good	Fair	Poor
CM = 1	V < 30 in. then CM = 0.95 V ≥ 30 in. then CM = 1	CM = 0.9
For containers of optimal design, such as some boxes and crates, a “good” hand to object coupling would be defined as handles or handhold cutouts	For containers of optimal design a “fair” hand to object coupling would be defined as handles or handholds of less than optimal design (hand cannot form a 95° angle)	Container of less than optimal design or loose parts or irregular objects that are bully or hard to handle
For loose parts or irregular objects, which are not usually containerized such as casting and stock, a “good” hand to object coupling would be defined as comfortable grip in which the hand can be easily wrapped around the object		Lifting nonridge items

Table 14.10  Work Practices Lifting Guide Frequency Look-Up Table

Frequency (lifts/min)	≤1 h	>1 h but ≤2	>2 h but ≤8
	V < 30 in.	V > 30 in.	V < 30 in.	V > 30 in.	V < 30 in.	V > 30 in.
0.2	1	1	0.95	0.95	0.85	0.85
0.5	0.97	0.97	0.92	0.92	0.81	0.81
1	0.94	0.94	0.88	0.88	0.75	0.75
2	0.91	0.91	0.84	0.84	0.65	0.65
3	0.88	0.88	0.79	0.79	0.55	0.55
4	0.84	0.84	0.72	0.72	0.45	0.45
5	0.8	0.8	0.6	0.6	0.35	0.37
6	0.75	0.75	0.50	0.50	0.27	0.57

The RWL is a simple calculation once all the factors have been accounted for. The RWL is a starting point and is a recommendation based on the parameters of the lift. The RWL is used to calculate the lifting index.

1. LI = Actual Weight of the Load/RWL

1. Interpretation: increased risk of low back injury if the LI exceeds 1

2. <1 OK

3. =1 OK

4. >1 may have increased risk

5. >3 likely have increased risk.

Some believe that if workers are properly screened (based on the task requirements) and trained, they can safely work at lift indexes greater than 1 but less than 3.

Other Tools

The healthcare, hand tools, and manual material handling sections of this text include additional assessment tools as well as  Appendix C .

SUMMARY

Workers exposure to physical workplace risk factors can be evaluated using many methods and no one method is correct in all situations. It is recommended that a variety of methods are used to improve the fit between the worker and the workplace.

While it is near impossible to eliminate a worker exposure to all the physical workplace risk factors, they can be reduced to lessen the probability of injury since it is the combination of risk factors that increase injury probability. For example, in a situation that has a high exposure to force in an awkward posture, changing the posture to neutral will reduce the force component as well. Small changes can make a large impact on a worker's overall exposure profile.

Control options can be identified and developed for each of the physical workplace risk factors found. A sound technique is to evaluate each solution against each other in a cost-benefit trade-off analysis.

Keep in mind the four basic approaches to controlling risk hazards proceeding from eliminating the hazard to using administrative controls. Full descriptions of the hazard control options are listed below in order of highest to lowest priority. As with other industrial hygiene and safety methods for controlling hazards, elimination, engineering, and substitution are preferred over administrative. In the context of ergonomics, few PPE solutions exist when it comes to hazard control.

A useful approach is to provide the risk reduction against each hazard control option and use it for a tired approach ( Table 14.11 ).

Table 14.11  Hierarchy of Control

Levels of Hazard Control

1. Elimination – A redesign or procedural change that eliminates exposure to an ergonomic risk hazard; for example, using a remotely operated soil compactor to eliminate vibration exposure 2. Engineering controls – A physical change to the workplace; for example, lowering the unload height of a conveyor 3. Substitution – An approach that uses tools/material/equipment with lower risk; for example, replacing an impact wrench with a lower vibration model 4. Administrative – This approach is used when none of the above can be used or are impractical to implement. Administrative controls are procedures and practices that limit exposure by control or manipulation of work schedule or the manner in which work is performed. Administrative controls reduce the exposure to ergonomic stressors and thus reduce the cumulative dose to any one worker. If you are unable to alter the job or workplace to reduce the physical stressors, administrative controls can be used to reduce the strain and stress on the work force. Administrative controls are most effective when used in combination with other control methods, for example, requiring two people to perform a lift

KEY POINTS

· Small changes to a worker's exposure to the physical risk factors can result in a major impact on their safety, health, and overall well-being.

· Many tools exist to evaluate the physical workplace risk factors, but no tool is encompassing and therefore using multiple tools is a good approach.

REVIEW QUESTIONS

1. What are the four major parts of an assessment?

2. What tools should be brought to an assessment?

3. What is a limitation of the ACGIH TLV for lifting?

4. What is a limitation of the NIOSH WPLG?

5. What factors should be considered when evaluating a lifting task?

EXERCISE

1. Reference the Exercise appendix.

REFERENCES

1. Borg, G. (1998). Borg's Perceived Exertion and pain Scales. Champaign, IL: Human Kinetics.

2. Department of Defense. (1999). MIL-STD-1472F, Department of Defense Design Criteria Standard: Human Engineering. United States Government Printing Office.

3. Marras, W. S. & Karwowski, W. (2006). Interventions, Controls, and Applications in Occupational Ergonomics. The Occupational Ergonomics Handbook 2nd edn. CRC Press.

4. Snook, S. H., & Ciriello, V. M. (1991). The Design of Manual Handling Tasks: Revised Tables of Maximum Acceptable Weights and Forces. Ergonomics, 1197–1213.

5. Snook, S. H., Campanelli, R. A., & Hart, J. W. (1978a). A Study of Three Preventative Approaches to Low Back Injury. Journal of Occupational Medicine, 478–481.

ADDITIONAL SOURCE

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

2. MacLeod, D. (1994). The Ergonomics Edge: Improving Safety, Quality, and Productivity. Industrial Health and Safety. Wiley.

3. McAtamney, L., & Corlett, E. N. (1993). RULA: A Survey Method for the Investigation of Work-Related Upper Limb Disorders. Applied Ergonomics, 91–99.

1. Opnavinst. (n.d.). Navy Occupational Safety and Health Instruction 5100.23G.2307. Retrieved February 2015, from Department of the Navy Issuances: https://acc.dau.mil/adl/en-US/377924/file/51114/ref%20r_ONI5100.23G_Navy%20SOH%20Manual.pdf.

2. Pheasant, S. (1991). Ergonomics, Work and Health 1st edn. Aspen.

3. Schumann, W. O., and Konig, H. (1954). The Observation of Atmospherics at the Lowest Frequencies. Retrieved from The Healers Journal: http://www.thehealersjournal.com/2012/05/21/the-schumann-resonance-earths-powerful-natural-vibration/#sthash.qrXSOhWM.dpuf.

4. Snook, S., Campanelli, R. & Hart, J. (1978b). A study of three preventative approaches to low back injury. Journal of Occupational Medicine, 20(7), 478–481.

5. The Ergonomics Group, Health and Environmental Laboratories, Eastman Kodak Company. (1989). Ergonomic Design for People at Work, vol. 2. Wiley.