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An Ergonomic Analysis of the Current Lifting Techniques

in Height Restricted Cargo Bins

at Company XYZ

by

Scott Rud

A Research Paper Submitted in Partial Fulfillment of the

Requirements for the Master of Science Degree

III

Risk Control

Approved: 2 Semester Credits

ale t -'- If /1// c~,~ti'tvv~ ~~-'VV\ l :vV Dr. Elbeli Sorrell

The Graduate School

University of Wisconsin-Stout

April, 2011

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The Graduate School

University of Wisconsin-Stout

Menomonie, WI

Author: Rud, Scott A.

Title: An Ergonomic Analysis of Current Lifting Techniques in Height

Restricted Cargo Bins at Company XYZ

Graduate Degree/ Major: MS Risk Control

Research Adviser: Dr. Elbert Sorrell

Month/Year: April, 2011

Number of Pages: 61

Style Manual Used: American Psychological Association, 6th

edition

Abstract

The aviation industry has one of the highest rates for back strains, shoulder strains and

long term MSDs. Company XYZ has experienced a higher than industry average injury rate due

to the limited height in the cargo bins and the restricted posture lifting. The continued presence

of higher than industry average back and shoulder strains and sprains in the height restricted

cargo bins at Company XYZ is placing the organization at risk of incurring continued employee

injury and other workers compensation related forms of loss. The four years of OSHA

recordable injuries, the results of the ergonomic-based risk factor assessment methods of the

Rapid Upper Limb Assessment (RULA) and Rapid Entire Body Assessment (REBA), and the

NIOSH lifting equation were compared to recognition and remediation measures for

musculoskeletal disorders (MSDs) that have been identified in professional literature on the

topic. The research results indicate that awkward postures and high repetition are the major

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causes for musculoskeletal disorders, back and shoulder sprains and strains and flexion of the

neck and spine. The conclusions of this research are that a selection of administrative controls

and personal protective equipment are used to educate the workers and reduce the risk factors

from lifting in the height restricted cargo bin. Since the elimination of these risk factors is not

feasible, reduction through proper training, implementation and employee cooperation is the

goal.

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Table of Contents

Page

Abstract ...................................................................................................................................... 2

List of Tables ............................................................................................................................. 6

List of Figures ............................................................................................................................. 7

Chapter I: Introduction ............................................................................................................... 8

Statement of the Problem ............................................................................................... 10

Purpose of the Study ....................................................................................................... 10

Goals of This Study ........................................................................................................ 10

Limitations of the Survey ............................................................................................... 10

Assumptions of the Survey ............................................................................................ 11

Definition of Terms ....................................................................................................... 11

Chapter II: Literature Review ................................................................................................... 13

Benchmarking Ergonomic Losses .................................................................................. 13

Ergonomic Risk Factors.................................................................................................. 17

Ergonomic-Related Injuries/Illnesses .............................................................................. 18

Task Analysis ................................................................................................................. 20

Ergonomic Job Analysis ................................................................................................. 20

Ergonomic Controls ........................................................................................................ 25

Engineering Controls ...................................................................................................... 26

Administrative Controls .................................................................................................. 27

Personal Protective Equipment (PPE) ............................................................................. 28

Summary ....................................................................................................................... 28

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Chapter III: Methodology ......................................................................................................... 30

Subject Selection and Description .................................................................................. 30

Instrumentation .............................................................................................................. 32

Data Collection Procedures ............................................................................................ 33

Data Analysis ................................................................................................................ 36

Limitations .................................................................................................................... 38

Summary ....................................................................................................................... 38

Chapter IV: Results .................................................................................................................. 39

Objective One ................................................................................................................ 39

Objective Two ............................................................................................................... 40

Objective Three .............................................................................................................. 43

Discussion ..................................................................................................................... 50

Chapter V: Summary, Conclusions and Recommendations........................................................ 52

Methods and Procedures ................................................................................................. 52

Major Findings ............................................................................................................... 53

Conclusions .................................................................................................................... 55

Recommendations .......................................................................................................... 56

Engineering Controls ...................................................................................................... 57

Administrative Controls .................................................................................................. 57

Personal Protective Equipment ....................................................................................... 58

Recommendations for Further Study ............................................................................... 59

References ............................................................................................................................... 60

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List of Tables

Page

Table 1: Company XYZ’s Performance Trends ..................................................................... 40

Table 2: Industry Averages .................................................................................................... 41

Table 3: TRCR Comparison .................................................................................................. 42

Table 4: DART Comparison .................................................................................................. 43

Table 5: One Minute Repetition Average............................................................................... 49

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List of Figures

Page

Figure 1: Rapid upper limb assessment worksheet ................................................................. 22

Figure 2: Rapid entire body assessment worksheet ................................................................ 24

Figure 3: Top view of cargo bins one and two ....................................................................... 31

Figure 4: Side view of cargo bins one and two ....................................................................... 32

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Chapter I: Introduction

Ergonomics is the science of fitting workplace conditions and job demands to the

capabilities of the working population (Occupational Safety and Health Administration,

Ergonomics, 2010). Ergonomic hazards exist in a multitude of industries and according to the

2008 OSHA incident rates the aviation industry ranks as one of the top industries for total non-

fatal occupational injuries (OSHA, 2008). There are a variety of ergonomic risk factors that

contribute to injuries in the luggage handling process of the airline ground handling industry.

These risk factors would include, restricted posture lifting, repetitive lifting, forceful lifting,

overexertion, pulling and pushing, and frequent heavy lifting. Working inside the height

restricted cargo bins have multiple risk factors which can lead to a higher than average

probability of causing long term Musculoskeletal Disorders (MSDs).

Incident rates of lost time MSDs such as shoulder and back strains in the airline ground

handling industry are some of the highest in all the private industry. The overall incident rate is

3.5 times the rate for private industry as a whole; rates of back and shoulder injuries are four and

five times the respective rates for private industry as a whole (Korkmaz et al 2005).

These MSDs evolve over an extended period of time due to the repetitive nature, frequent

heavy lifting and the posture restricted duties performed. Loading the height restricted cargo

bins is an extremely demanding job that possesses several ergonomic hazards. Long term risk

exposure to restricted posture lifting in time sensitive conditions are of great concern to the

ground handling industry.

Company XYZ is a ground handling company that performs the luggage handling

procedures for major airlines. They operate in over 100 different locations, employ over 5,000

ground handling employees and perform these duties in all types of weather conditions.

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Theoretically the process of performing the job is the same in each location as stated in Company

XYZ’s standard operating procedures manual. Realistically the challenges are many; those

challenges include different training styles, management styles, work ethics, and culture. There

are many unique challenges to this type of work, even with a standardized process the only real

constant factor is the limited height restrictions inside the cargo bin. Company XYZ has

demonstrated a strong commitment to their employee group, their share holders and the

communities with safety being their top core value. Commitments include but are not limited to,

training proper lifting techniques, pre and post stretching activities, and engineering controls

with self-propelled belt loaders. Self-propelled belt loaders are motorized pieces of equipment

that assist in moving luggage from the ground level to the cargo bins by the use of conveyor

belts. This piece of equipment reduces the employees risk exposure to repetitive lifting and

lifting above their shoulders, though all loading activities inside the cargo bins are manually

performed by the employees.

The maximum center height of the cylinder shape cargo bins in this study is 64” (5’4”)

with the front loading area measuring 58” (4’8”). The problem exists of how to properly lift

when your space is limited if the mean height of a man a 1999-2002 was approximately 69” and

for woman was approximately 64” (Center for Disease Control and Prevention, CDC 2004).

Some employees may fall in the range where proper lifting techniques can be performed, though

hiring individuals that meet height requirements to properly lift in these spaces are not feasible.

The commitment of Company XYZ of continuous improvement shows a high emphasis

to the safety, health and well-being of their employees. However, back strains, shoulder strains,

and long term MSDs are still occurring above the industry average and alternate means of

performing these job functions in a safer manor are needed.

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Statement of the Problem



to the limited height in the cargo bins and the restricted posture lifting.

Purpose of the Study

The purpose of this analysis is to determine the root causes of back injuries sustained

during the loading process inside the height restricted cargo bins. From this root cause analysis

an ergonomic solution can be derived to help reduce the severity of back injuries or ultimately

eliminate them.

Goals of This Study

1. Conduct an analysis of safety metrics of Company XYZ to better understand their

safety related performance and historical trends.

2. Conduct a review of national aviation accidents statistics to use as a basis for

comparison to Company XYZ.

3. Conduct task analysis of manual material handling activities performed by

employees in height restricted cargo bins at Company XYZ.

Limitations of the Study

1. This study is limited to only the lifting techniques inside the cargo bins of a

commercial aircraft.

2. No considerations will be made for lifting techniques outside the defined research

area.

3. This study is only for the purpose of identifying alternate lifting techniques to be

used in the height restricted spaces of a commercial aircraft cargo bin.

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4. These techniques will offer alternate methods of properly lifting to reduce the risk

exposures, lower the back and shoulder strains and to provide guidance for

training exercises.

Assumptions of the Study

1. The employee’s willingness to participate with this study may alter the results.

2. The employee’s willingness to perform their job functions in the same manor as

they would during a non observed day.

3. The employee’s will not alter there normal work practice or habit to adhere to the

current study.

4. The process analyzed, conclusions, and recommendations for this study pertain

only to the proper lifting techniques inside the aircraft cargo bin.

Definition of Terms

Engineering Controls. Physical changes to work stations, equipment, materials,

production facilities, or any other relevant aspect of the work environment that reduce or prevent

exposure to risk factors.

Ergonomics. Ergonomics is the science of fitting workplace conditions and job

demands to the capabilities of the working populations.

Ground Handling Company. Ground handling addresses the many service

requirements of a passenger aircraft between the time it arrives at a terminal gate and the time it

departs on it next flight. Speed, efficiency and accuracy are important in ground handling

services in order to minimize the turnaround time (the time during which the aircraft must

remain parked at the gate).

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Musculoskeletal Disorders (MSD). Disorders of the muscles, tendons, ligaments,

joints, cartilage, nerves, blood vessels, or spinal discs. Some examples are muscle strains,

ligament sprains, joint and tendon inflammation, pinched nerves, and spinal disc degeneration

(Chengular, et al., 2004).

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Chapter II: Literature Review

The purpose of this study was to conduct an ergonomic analysis of the current lifting

techniques in the height restricted space of a commercial airline cargo bin at Company XYZ.

The current lifting techniques can potentially expose the employees of Company XYZ to long

term musculoskeletal disorders, back and shoulder sprains and strains, flexion of the neck and

spine, abduction of arms, unilateral foot coupling and ulnar deviation of the wrists. The review

of literature, details current employee injury rates related to the luggage handlers in the aviation

industry, the ergonomic risk factors associated with musculoskeletal disorders, the tools used to

analyze the current lifting techniques, and the tools or controls which are used to implement the

best form of correction. Through the recognition of improper ergonomic lifting techniques, body

positioning and the implementation of correct techniques it may be possible to decrease the

current injury rates.

Benchmarking Ergonomic Losses

Benchmarking is the process of identifying standards to use in comparison of practices,

activities or standards (Teachnology, 2010). Creating a benchmark standard can help a company

compare if the losses of a company have increased or decreased. Benchmarking of loss is

divided into two main categories, reactive loss or lagging indicators and proactive loss or leading

indicators. Reactive loss response occurs after an injury or illness and usually has the purpose

of minimizing the costs associated with the injury or illness (OSHA, 2010). Whereas proactive

loss response takes place before an accident has occurred. It anticipates and tries to prevent

accidents.

Reactive Loss . Reactive loss or lagging indicators are after-the-fact measurements that

gauge past performance, such as OSHA incidence rates and injury and incident costs (Morrison,

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2010). This reactive approach provides better administration and temporary relief, but the effort

and investment must continue indefinitely because the root causes of the injuries are never

addressed (EHS Today, 2010). There are multiple reactive measures that a company can utilize

to compare past injury rates to the current incident rates. Incident rates take on more meaning

for an employer when the injury and illness experiences of their firm is compared with that of

other employers doing similar work with workforces of similar size (Bureau of Labor and

statistics, 2010). This type of measurement is dependent on incidents to drive their safety

activities and may reflect no more than random fluctuations and is not a valid indicator of safety

improvement (Dial, 1992). One of these reactive methods of measurement is the OSHA

recordable incident rate. This incident rate only takes into consideration recordable incidents and

is computed using an OSHA standard formula. The number of injuries and illnesses x 200,000

divided by the total employee hours worked will give you the incident rate. The 200,000

represents 100 employees working 40 hours per week and 50 weeks per year. An OSHA

recordable incident includes all work related deaths, illnesses and injuries which result in a loss

of consciousness, restriction of work or motion, permanent transfer to another job within the

company or that require some type of medical treatment or first aid (OSHA, 2010).

Another reactive measurement tool is using the Days Away, Restrictions and Transfers

(DART). The DART rate looks at the amount of time an injured employee is away from his or

her regular job. To compute the DART rate, multiply the number of DART incidents times

200,000, and divide again by your company’s total labor hours (Gokey, 2010). This reactive

measure is base only on those injuries and illnesses severe enough to warrant Days Away,

Restrictions or Transfers. Lost time case rate (TCR) is another reactive measuring tool. The

TCR considers only incidents in which workdays were lost. Here again you multiply your

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number of lost time cases by 200,000, and divide the result by the total number of hours worked

by your employees. And, once again, the result tells you how many employees lost time per 100

employees on your payroll (Gokey, 2010). Severity rate is another reactive measuring tool, this

looks at incidents in terms of the actual number of days that were lost on average. To calculate

the Severity Rate, you simply divide the number of lost workdays by the number of recordable

incidents (Gokey, 2010). Lastly, one of the most important reactive measuring tools is the

claims made and the monetary amount paid out for workers compensation. Workers

compensation is a state law mandated by the federal government that provides compensation

medical care for employees who are injured in the course of performing work functions

(Wikipedia, 2010). Using workers compensation as a reactive tool can help evaluate the

probability and severity of future workers compensation claims by utilizing historical claims

data. Evaluating the nature, severity and frequency of those claims has potential to identify areas

that have a higher probability for reoccurrence. A rise in workers compensation premiums can

be directly related to direct costs such as medical and compensation expenses, but in indirect

costs as well. Losses of production, time, employee morale and client goodwill are all indirect

costs that are hard to calculate (Yager, 2008).

For many companies, using reactive incident rates remain their primary method of

tracking company safety performance. Even when statistically valid, incidence rates are still less

desirable than a proactive approach that can predict incidents before they occur. The knowledge

that incidents are significantly increasing, even if founded on sound evidence, provides no

information as to the causes or means to correct them (Dial, 1992). The reasoning behind this is

due to the simplicity of calculating the injury rate, the ease of comparison between companies

that provide the same service and product, and are used by OSHA and industry.

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Proactive Loss. Proactive loss or leading indicators are a measure of future

performance, management commitment or systems to drive performance change (Morrison,

2010). The proactive approach to controlling loss is where companies begin to take a risk

management approach to managing work related musculoskeletal disorders (EHS Today, 2010).

It is the prevention of injuries and illnesses in the workplace before they occur. There are

methods used in the proactive approach to loss response, these methods would include, job safety

analysis, routine task and job hazard analysis, employee interviews, initial, recurrent and

specialized training, surveys, and questionnaires. Reported benefits of such interventions include

lowering the numbers and costs of injuries, reducing discomfort and fatigue, and improving

productivity (Marras, et al., 2000). Along with these reported benefits, leading indicators give a

more accurate picture of any company and can provide positive reinforcement for a job being

done correctly (Morrison, 2010). Interviews, surveys and questionnaires are an informative

method used to gather employee input on the job processes they are performing. These

informative methods can gather information electronically (computer based questionnaire) or

paper based. A questionnaire can be extremely reliable if it elicits the same response under the

same conditions and proctored by the same individual. Reliability is essentially about

repeatability of results either by another observer or the same observer at different times or under

different circumstances (Annett, 2002). These questionnaires are developed to extract attitudes

and perceptions of employees toward their work environment, job duties, and can be used in the

recording of information to be used for future changes or training sessions.

A paralleling proactive active approach is the completion and performance of work place

assessments, audits and inspections. Audits are designed to rate an organization’s total safety

and health program, identify its strengths and weaknesses, show were improvements are needed,

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and obtain commitment and target dates for correcting problems (The Hartford, 2002). In other

words, a proactive approach is a process orientated approach that emphasizes employee

contributions to the development and implementation of various controls that are directed at the

reduction of overall loss (National Safety Council, 2010).

Safety training. A proactive approach and critical factor to any company’s safety

management program is training. Most training interventions lead to positive effects on safety

knowledge, adoption of safe work behaviors and practices and safety and health outcomes

(Burke, et al., 2006). The purpose of proper training and education is to provide all levels of

employees with the correct information so they take ownership in their roles to reduce work

place injuries. Most organizations follow a strong vertical accountability. This type of

accountability tends to ensure compliance rather than commitment and goal focus (Ray, et al.,

2007). Ensuring that employees take ownership in their wellbeing is an important element to the

success of a proper training program. Training all levels in horizontal accountability instead of

vertical accountability will provide the necessary support within the same levels of the

organization. Horizontal accountability is the degree to which people communicate across the

organization, problem solve with all employees and teams, and build accountability for superior

outcomes (Ray, et al., 2007). Training and education at all levels of an organization in the signs

and symptoms related to MSDs, ergonomic issues and efficient early reporting will help this

company be proactive in taking proper action to reduce the severity of injuries.

Ergonomic Risk Factors

There are four major ergonomic risk factors that are associated to the contribution of long

term musculoskeletal injuries (MSIs). Those four work related factors are high pace of work,

excessive forces, fixed or constrained postures, and high repetition (Canadian Centre for

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Occupational Health and Safety, 2010). It is very important to know that MSIs and specifically

repetitive motion injuries (RMIs) rarely originate from one event or a particular factor. With

repeated or sustained muscle activity and in jobs in which the same motor units are used

extensively and repeatedly with small variations in working conditions, muscle fatigue is likely

to develop (Faucett, et al., 2002). Continuous muscle fatigue with the same repetitive motion is

the predecessor for RMIs. For this study restricted postures for spinal loading are the main

concern though high repetition and excessive forces are both contributing factors. Given that

forces from the active trunk muscles are the primary determinant of spinal load, increased

muscle loading associated with restricted postures impose increased spinal loading (Splittstoeser,

et al., 2007). Fixed or constrained postures is a body position that overloads muscles and

tendons or loads joints in an uneven or asymmetrical manner, typically from the deviation of the

neutral positions of the different body parts. Fixed or constrained postures typically include

reaching above, behind, twisting, forward or backward bending, pinching, squatting and

kneeling.

Ergonomic-Related Injuries/Illnesses

According to the Bureau of Labor and Statistics (2001) baggage handlers and airlines had

the highest total recordable injury rate of all industries. With an injury rate exceeding 13 injuries

per 100 employees in 2001, working at the airline is more hazardous than basic steel production,

lumberjacking, heavy construction, and more than double the average of all industries in the

private sector combined (BLS, 2001). That number has decreased to 8.5 injuries per 100

employees in 2009 according to the BLS, though still amongst the highest in the industry.

Ergonomic risk factors associated with the lifting techniques in the aviation industry

cover all aspects of employee injury; however, for this study the injuries most concerning are

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shoulder and lower back musculoskeletal disorders. Musculoskeletal disorders (MSDs), often

referred to as ergonomic injuries, are injuries or illnesses affecting the connective tissues of the

body such as muscles, nerves, tendons, joints, cartilage, or spinal disks (Bureau of Labor and

Statistics, 2007). It is well accepted that the manual handling of work is probably associated

with work-related lower back disorders (Yeung, et al., 2003). Among the physical risk factors,

scientific evidence indicates manual lifting as a strong predictor of the development of low back

complaints at work (Hoozemans, et al., 2008). Hand and wrist, neck, and elbow (Epicondylitis)

disorders are contributing factors and should not be overlooked however the majority of lifting

injuries are to the shoulders and back.

There is evidence for a positive association between highly repetitive work and shoulder

MSDs (National Institute for Occupational Health and Safety, 1997). The National Institute for

Occupational Health and Safety stated that prior to 1997 there had only been three studies that

specifically addressed shoulder tendinitis. These studies involve combined exposure to

repetition with awkward shoulder postures or static shoulder loads (NIOSH, 1997). Repetitive

motion is a persistent and continual movement that can cause localized musculoskeletal injuries

or illness. This type of motion is a large part of the luggage handlers’ duty during the loading

process of the cargo bins. Awkward shoulder and back postures are a result of the height

restrictions these employees face while performing lifting techniques inside the cargo bins.

Since the shoulder is the most mobile joint in the human body, the cost of such versatility is an

increase risk of injury (Quillen, et al., 2004).

Although low back pain is the most common disabling musculoskeletal symptom, there is

little understanding regarding the risk factors (Frymoyer, 1983). A lower back strain occurs

when the muscle fibers are abnormally stretched. Lower back sprains occur when the ligaments

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are torn from their attachments. These two conditions can occur from flexion of the back during

improper lifting techniques, awkward trunk posture, improper lifting techniques, unilateral foot

coupling and lifting heavy objects away from the body. Awkward trunk posture is the most

prevalent of these five distinct movements and positions all of which are typical to the loading

processes of luggage inside cargo bins. Awkward trunk postures, such as flexion, lateral

bending, and twisting, increase the likelihood of back injuries, particularly during lifting

(Keyserling, et al., 1991).

Task Analysis

Methods of collecting, classifying and interpreting data on human performance in work

situations lie at the very root of ergonomics. Task analysis, as these methods are collectively

known, reflects both our current understanding of human performance and the design of systems

that best serve the needs of human users (Annette & Stanton, 1998). The job task analysis is a

process by which a task is broken down into its component parts and produces three important

tools, task lists, job breakdowns and job performance standards (Andrea, 2009). Task analysis is

the big picture, by breaking a task down into smaller components you can begin to determine

root causes. For this study a smaller component of a task analysis, an ergonomic job analysis,

will be studied.

Ergonomic Job Analysis

Ergonomic job analysis is an open-ended process that involves detailed inspection,

description, and evaluation of the workplace, equipment, tools, and work methods (Keyserling,

et al., 1991). There are multiple tools available for a job analysis in assessing the lifting

techniques, body positions and forces needed to perform the required functions inside the cargo

bins. All assessment tools are used to determine the extent of the present symptoms. These tools

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include the rapid upper limb assessment (RULA), the rapid entire body assessment (REBA), the

national institute for occupational safety and health equation (NIOSH), digital inclinometer, and

the hydraulic push-pull dynamometer. These ergonomic job analysis methods measure the body

positioning and movement performance required during normal luggage loading procedures.

Rapid Upper Limb Assessment (RULA). The RULA method has been developed by

Dr. Lynn McAtamney and Professor E. Nigel Corlett, ergonomist from the University of

Nottingham in England (see Figure 1). Rapid Upper Limb Assessment is a survey method

developed for use in ergonomic investigations of workplaces where work related upper limb

disorders are reported (McAtamney, 1993). A RULA assessment gives a quick and systematic

assessment of the postural risk to a worker (Cornell University Ergonomics Web, 2010). Since

the RULA method needs no specialized tools, minimal training can be provided to employees to

perform the ergonomic based assessments. The RULA method is a quick method for

determining upper body posture risks to employees which uses diagrams of body postures and

scoring tables to evaluate risk exposure factors. Completing a RULA on a job task prior to

making changes will give you a risk factor for comparison. Once changes to the job task have

been implemented a post RULA should be performed to determine if the changes made have

lowered the risk factor. Risk factors addressed on this form are:

Force

Abduction and Adduction

Pronation and Supination

Flexion and Extension

Static Muscle Work

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Figure 1. Rapid Upper Limb Assessment Worksheet

Rapid Entire Body Assessment (REBA). The REBA was developed by Dr. Sue

Hignett and Dr. Lynn McAtamney in 1993 to associate the risk of musculoskeletal injury with

the recorded postures (see Figure 2). Rapid Entire Body Assessment has been developed to fill a

perceived need for a practitioner’s field tool, specifically designed to be sensitive to the type of

unpredictable working postures found in health care and other service industries (Hignett &

McAtamney, 2000). According to Hignett and McAtamney the development of REBA was

aimed to:

Develop a postural analysis system sensitive to musculoskeletal risks in a variety of

tasks.

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Divide the body into segments to be coded individually, with reference to movement

planes.

Provide a scoring system for muscle activity caused by static, dynamic, rapid

changing, or unstable postures.

Reflect that coupling is important in the handling of loads but may not always be via

the hands.

Give an action level with an indication of urgency.

Require minimal equipment – pen and paper method (Hignett & McAtamney, 2000).

The REBA is a worksheet used to assess entire body movements during specific tasks.

The worksheet is a good tool when looking at movements such as the neck, trunk, legs, upper

arms, lower arms, and wrists. There is only minimal input needed which tends to be a weakness

when looking at risk factors. The number system used to rank the severity of hazards works well

with this assessment tool as long as the values are only used for the intended job task. This tool

may not take into account all aspects of the task being performed; however it does provide a

starting point where the highest potential for injury can occur.

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Figure 2. Rapid Entire Body Assessment Worksheet

NIOSH lifting equation. The NIOSH lifting equations is a tool used to identify,

evaluate or classify risks associated with a lifting task. This equation will calculate the

Recommended Weight Limit (RWL) and the Lifting Index (LI). The RWL is the recommended

weight of the load that nearly all healthy workers could lift over a period of time (up to eight

hours) without an increased risk of developing lifting related low back pain or injury, given all

other task parameters remain unchanged. The LI is a relative estimate of the physical stress

associated with a manual lifting job. As the magnitude of the LI increases, the level of the risk

for a given worker increases, and a greater percentage of the workforce is likely to be at risk for

developing lifting-related low back pain. This tool is used for:

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Estimating the risk of a two-handed, manual lifting task.

Evaluating a job characterized by multiple lifting tasks.

Evaluating a lifting task that may include trunk rotation, different types of hand

coupling, repetitiveness, and duration.

Determining a relatively safe load weight for a given task.

Determining a relatively unsafe load weight for a given task.

Deciding the appropriate style of abatement for a job that has been identified as

having a lifting hazard.

Comparing the relative risk of two lifting tasks.

Prioritizing jobs for further ergonomic evaluation (Ergoweb, 2010).

Key variables for the NIOSH lifting equations are Load Constant (LC), Horizontal Multiplier

(HM), Vertical Multiplier (VM), Distance Multiplier (DM), Asymmetric Multiplier (AM),

Frequency Multiplier (FM), and Coupling Multiplier (CM).

Ergonomic Controls

To reduce injury, we must reduce hazards and at-risk behaviors. Once hazards are

identified they should be reduced or eliminated. This can be done by either designing

engineering controls, administrative controls or training, and finally if none of the above controls

are possible, personal protective equipment should be used (Roberts, 2007). Engineering

controls are used to eliminate the risk of injury by redesigning the process or the equipment.

Administrative controls eliminate or reduce the risk of injury by removing the worker from the

process. Personal protective equipment is used to reduce the hazards an employee is exposed to,

but does not eliminate the hazard. For this control to be effective, the employee must adhere to

use, care and training for each PPE used.

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Engineering Controls

Engineering controls are the most preferred method for controlling ergonomic risk factors

because they are more permanent and effective (OCAW, 2010). Engineering controls are

physical changes to workstations, equipment, facilities, or production that reduce or prevent an

employee’s exposure to risks. Engineering controls include modifying, redesigning or replacing:

Work stations and work areas

Materials/objects/containers design and handling

Hand tools used

Equipment (OWAC, 2010)

Engineering controls tend to be the most effective form to reduce workplace hazards,

employee hazards, and overall risk, however this form tends to be time consuming and more

expensive than the other two. Engineering controls utilize an engineer to redesign the equipment

or process to fit the individual needs of the employees. Engineering control strategies used to

reduce the ergonomic risk factors can include the following:

Modifying tables to adjust in height to meet the needs of all employees.

Modifying working surfaces to tilt toward an employee. This will allow individuals

to work on a surface in a more natural posture.

Reducing or eliminating the use of hand tools and changing them to low vibration

power tools.

The use of a hydraulic lifting devise to eliminate the need for employees to manually

lift items above their shoulder, away from there body or in awkward positions.

Designing a work area that is uncluttered, and creates a streamline process. This will

eliminate or reduce excess manual lifting or moving of products.

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Employees are a key asset to the implementation of engineering controls due to there

knowledge of the processes, materials and job demands. The utilization of employees during the

design phase, the testing phase and the rollout phase can help to ensure employee acceptance and

to insure the needs of the employees are met.

Administrative Controls

Administrative control is defined as any procedure that significantly limits daily exposure

by control or manipulation of the work schedule or manner in which work is performed

(Workrite, 2010). Administrative controls include but are not limited to:

Job rotation, use of rest breaks or alternative tasks.

Job enlargement to increase task variability.

Redesign of work methods.

Adjustment of work pace or number of repetitions (Workrite, 2010).

Reduction of overtime.

Training.

Although engineering controls is the preferred method of reducing work place hazards,

administrative controls can be effective when it is impossible to engineer out a hazard. An

example where engineering controls would not be the preferred method would be the cargo bins

of commercial airlines. You can not make the cargo bins taller with out redesigning the entire

fuselage of the aircraft, if you make the fuselage larger you need larger engines, larger engines

require more fuel and so on. In this example engineering controls are not feasible, with the

preferred methods being administrative controls and Personal Protective Equipment (PPE).

28

Personal Protective Equipment (PPE)

Personal Protective Equipment is any item worn by an employee that would help reduce

or control the risk factors while performing their job duties. Respirators, ear plugs, safety

goggles, chemical aprons, safety shoes and hard hats are all examples of PPE. This method

should be used as a principle means of control only as a last resort when neither engineering nor

administrative controls are possible, or in the event of an emergency (OCAW, 2010). This type

of control does not reduce the hazard it only offers a barrier between the employee and the

hazard. The most effective method of reducing or eliminating ergonomic hazards is to fix the

hazard, not the worker, through engineering or administrative controls (OCAW, 2010).

Summary

Restricted posture lifting, repetition, forceful lifting, overexertion, frequent heavy lifting,

pulling and pushing effect the human body differently; however each can be attributed to the

onset of musculoskeletal disorders. This disorder is of great concern for the aviation industry

where engineering controls are limited. This industry must rely on administrative controls,

employee self monitoring and PPE to effectively reduce the injury rate. There are three distinct

assessment methods used in this study, RULA, REBA and the NIOSH lifting equation which are

essential for creating a baseline for comparison after the controls have been implemented. In

correlation with these assessment tools, ergonomic instruments such as the manual goniometer,

video analysis, digital inclinometer, and the hydraulic push pull dynamometer are used insure the

assessment methods are properly compiled.

Once the exposures and risks have been identified and evaluated establishment of the

hierarchy of control are used to reduce or eliminate the risk exposures. The hierarchy of controls

include, engineering controls, administrative controls and personal protective equipment. The

29

least effective of the controls are the personal protective equipment. Although PPE provides a

barrier between the employee and the work hazard it does have some drawbacks. Theses

drawbacks come from the employee’s willingness to participate and accept the changes,

recommendations and guidelines. The use of quantitative and qualitative assessments will allow

this company to reduce the risk exposures to their employees by being able to test, analyze and

recommend changes to the current work practice.

30

Chapter III: Methodology

The purpose of this study is an ergonomic analysis of the current lifting techniques

involved during the luggage loading process inside a commercial aircraft cargo bin at Company

XYZ. In order to analyze the ergonomic risks associated with the loading process several tools

will be used to determine the severity of risk factors associated with awkward postures, force,

repetition and heavy lifting away from the body. This chapter will explain the subjects tested,

the instrumentation used, data collection procedures, data analysis, and the limitations of the

analysis. The steps of this study were as follows:

A behavior observation was conducted over a two week period with out constructive

interactions from the observer.

Conducting a RULA, and REBA analysis and the NIOSH lifting equation to record and

compare job functions and the types of motions used during the cargo bin loading

process.

Perform video analysis to determine flexion, extension, force and foot coupling using a

manual goniometer, digital inclinometer, and hydraulic push-pull dynamometer.

Subject Selection and Description

There were two subjects observed and analyzed for this study. Subject 1 is a male, 46

years old, 6’1” tall and weighs 230 pounds. Subject 2 is a female, 40 years old, 5’8” tall and

weighs 196 pounds. A behavior observation was conducted over a two week period without

constructive interactions from the observers. Both subjects were asked to perform the same job

functions of loading and packing luggage into the SAAB 340 cargo bin (see Figure 3 and Figure

4 for a visual description of the cargo bins). Both subjects are full time employees working four

flights a day for five days a week. The average amount of luggage each subject moves per flight

31

is 39.33 bags with an average weight of 50 pounds per bag. Over a one year period this would

amount to working 1,000 flights and packing 39,330 bags for a total weight of 983.25 tons.

Subject one was observed performing luggage loading procedures in cargo bin one on his knees

with maximum trunk rotation. Subject two was observed performing this same task in an erect

position bending with the lower back and rotating the trunk. Since the maximum height of either

cargo bin is 64” (5’4”) both subjects were observed deviating from proper lifting techniques to

accommodate the confined and restricted space.

Figure 3. Top view of cargo bins one and two.

32

Figure 4. Three dimensional side view of cargo bins one and two.

Instrumentation

The specific tools used in this study include the RULA assessment survey, the REBA

assessment survey, the manual goniometer, a behavior observation, hydraulic push-pull

dynamometer and the NIOSH lifting equation. The two assessment surveys used in this study

are essentially alike, though each focuses on different adherent risks. They all rate movements

of the body to determine the potential severity of a work process, assign a number rating and a

risk level. For this study one survey would suffice however all three were used to compare the

findings for accuracy. The REBA focuses on the entire body with an emphasis on flexion and

extension. The RULA focuses on the muscular effort which is associated with posture, force,

and static or repetitive work which may contribute to muscle fatigue on the upper limbs. The

final scoring system of each tool will yield different numbers and scoring categories, but they

should conclude similar recommendations and outcomes.

A behavior observation was conducted over a two week period with out constructive

interactions from the observers. This observation was non invasive, offered no opinions and

33

fielded no questions. The observation was strictly used to study the current work habits of the

two subjects during normal operating procedures. The results from the behavior observation

exercises will help the researcher determine the ergonomic risk factors that are present in

Company XYZ’s cargo bin loading process.

The NIOSH lifting equation is a tool for assessing the physical stress of a two handed

manual lift task. As with any tool, its application is limited to the conditions for which it was

designed (Ergoweb, 2010). Although this equation was not designed to assess tasks in a

constrained or restricted work space, it was still performed to help validated the other surveys.

Three instruments will be used to produce ranges of motion, postural angles, and forces

exerted to load luggage inside the height restrict cargo bins of Company XYZ. The manual

goniometer is similar to a protractor which is used to determine postural angles. The digital

inclinometer is another tool used to determine postural angles. These two tools used to measure

postural angles where compared to each other to verify the accuracy of the angles observed and

recorded. The hydraulic push pull dynamometer measures the amount of force needed to lift

push or pull an object and can only take measurement in one direction at a time.

Data Collection Procedures

Completing the REBA Survey. The following are recommended steps for the proper

completion of a REBA survey.

1. Observe the entire task procedures to become familiar with the work practices.

2. Posture, force, coupling, duration and repetition activities involved with the loading

process inside the cargo bins will be selected and recorded in the appropriate boxes.

3. Postures are scored and totaled for sections A and B.

4. Sections A and B are then combine to form a single score.

34

5. An activity score is then calculated.

6. The final REBA score combines table C score with the activity score.

7. Changes to procedures or action levels are determined by the final score.

8. Risk levels are based on the final REBA score and range from negligible, low,

medium, high and very high.

9. Complete another REBA survey after desired changes have been made to determine if

those changes reduced or eliminated the risks identified.

Completing the RULA Survey. The following are recommended steps for the proper

completion of a RULA survey.


2. The part of the job duty to test is identified which includes the postures to assess.

3. The observer will score the postures and forces on the RULA diagrams for the

postures of each chosen body part.

4. Scores are then put into a table by following the instructions listed on the RULA

score sheet.

5. Changes to procedures or action levels are determined by the final score.

6. Complete another RULA survey after desired changes have been made to determine

if those changes reduced or eliminated the risks identified.

NIOSH Lifting Equation. The NIOSH lifting equations is a tool used to identify,

evaluate or classify risks associated with a lifting task. The NIOSH Lifting Equation will

calculate the Recommended Weight Limit (RWL) and the Lifting Index (LI). The RWL is the

recommended weight of the load that nearly all healthy workers could lift over a period of time

(up to eight hours) without an increased risk of developing lifting related low back pain or injury,

35

given all other task parameters remain unchanged. The LI is a relative estimate of the physical

stress associated with a manual lifting job. As the magnitude of the LI increases, the level of the

risk for a given worker increases, and a greater percentage of the workforce is likely to be at risk

for developing lifting-related low back pain. From the NIOSH perspective, it is likely that lifting

tasks with a LI > 1.0 pose an increased risk for lifting-related low back pain and injury for some

fraction of the workforce. NIOSH considers that the goal should be to design all lifting jobs to

achieve a LI of 1.0 or less. This tool is used for:

Estimating the risk of a two-handed, manual lifting task.

Evaluating a job characterized by multiple lifting tasks.

Evaluating a lifting task that may include trunk rotation, different types of hand

coupling, repetitiveness, and duration.

Determining a relatively safe load weight for a given task.

Determining a relatively unsafe load weight for a given task.

Deciding the appropriate style of abatement for a job that has been identified as

having a lifting hazard.

Comparing the relative risk of two lifting tasks.

Prioritizing jobs for further ergonomic evaluation (Ergoweb, 2010)



Frequency Multiplier (FM), and Coupling Multiplier (CM)

This study used the RULA, REBA and the NIOSH lifting equations and four ergonomic

instruments to collect and review the data. These methods included the Hydraulic Push-Pull

Dynamometer to determine the force needed to lift an object of known weight. The digital video

36

recorder to assess repetition, duration, body posture, hand coupling, uni-lateral and bi-lateral foot

placement. A digital camera was used to capture body posture, and then used those digital

photos to access angles of body posture by using the goniometer and digital inclinometer for

spine angle flexion.

Data Analysis

Manual Goniometer/Video Analysis/Digital Camera. The manual goniometer used in

this study was for the purpose of measuring the total flexion and extension angles of the back. A

goniometer is used to measure, in degrees, active or passive joint range of motion. This is

pertinent to workplace design and functional reach. It can also measure progress in return of

range of motion after an injury (Michael, 2002). This tool is useful in the determination of the

exact range of motion and when combined with the use of video or digital pictures can track the

full range of motion through the entire process. Comparing the data recorded in the study using

the goniometer to reasonable range of motion limits you are able to determine if limits were

exceeded.

Video analysis is the process of using a camera or digital video recorder to tape the

loading process. Multiple angles should be taped in order to get the most accurate joint angles,

extensions and flexions. Using a video recorder will allow the research to study the process in

real time speed or reduced speed. This also assists the researcher in breaking down the step by

step processes.


2. Set two video recorders up one at a ninety degree angle and one directly behind the

two subjects as they performed their job tasks. Record the movements performed

during the loading procedures.

37

3. Take digital photos throughout the loading process to help determine angles of

extension, flexion, abduction, adduction and reach.

4. Measure the joint angle by aligning the fulcrum of the goniometer with the fulcrum of

the joint to be measured.

5. Align the fixed arm of the goniometer with the limb being measured.

6. During the movement of the joint note the beginning point and the end point of the

joint being measured.

7. The degree between the beginning point and the end point determines the entire range

of motion.

8. A video monitor will be used to review the data and to help determine joint range of

motion and joint angles.

Digital Inclinometer. The digital inclinometer is an instrument for measuring angles of

slope and inclination of an object by creating an artificial horizon. For this study the digital

inclinometer was used to determine angles of the back and neck during standing loading

operations in the height restricted cargo bins.

Hydraulic Push-Pull Dynamometer. The Hydraulic Push-Pull Dynamometer was used

to determine the amount of force that each employee had to exert when lifting a piece of luggage

while performing the cargo loading tasks inside the height restricted cargo bins. This device

usually embodies a spring to be compressed or weight to be sustained by the force applied,

combined with an index, or automatic recorder, to show the work performed (Michael, 2002).

This is an essential part of this research since force, repetition and awkward angles in and of

themselves may not cause injury, however in combination will greatly increase the risk of injury.

The procedure used is as follows.

38

Hook the force gauge to a known object weighing 50 pounds (average weight of a piece

of luggage) and measure the force required for subjects one and two to lift that object.

Limitations

This study is limited to only the lifting techniques inside the cargo bins of a commercial

aircraft. No considerations will be made for lifting techniques outside the defined research area.

This study is limited to a specific time frame for observation and data collection. Since the turn

time of the aircraft used in the study is only 20 minutes all data collection had to be conducted

during this time. Turn time by definition is the amount of time it takes to service the aircraft

from off loading passengers and luggage to on loading passengers and luggage or from the

moment the brakes are set to the time they are released. Other limitations to this study are the

security requirements set by the Federal Aviation Administration, Company XYZ security

department and the airport authorities. The subjects tested must be willing participants who

perform their duties in the same fashion as if they were not being studied. This study is only for

the purpose of identifying alternate lifting techniques to be used in the height restricted spaces of

a commercial aircraft cargo bin. These techniques will offer alternate methods of properly lifting

to reduce the risk exposures, lower the back and shoulder strains and sprains and to provide

guidance for training exercises.

Summary

This chapter contained the purpose of the methodology, how the data was collected and

how that collected data was analyzed. The redundancy in data collection was to verify and

compare findings for accuracy and to be able to show that multiple testing procedures can result

in similar findings.

39

Chapter IV: Results

The purpose of this study was to analyze current lifting techniques inside the height restricted

cargo bins at Company XYZ in order to determine the extent that ergonomic-based risk factors

are present. The results of this study directly addressed the three main objectives:

1. Conduct an analysis of safety metrics of Company XYZ to better understand

their safety related performance and historical trends.





Objective One

To conduct an analysis of safety metrics of Company XYZ to better understand their

safety related performance and historical trends. For this objective four years were collected for

a fair comparison with the industry average and to understand any trends. The total recordable

case rate (TRCR) as well as the days away restricted or transfer rate (DART) for Company XYZ

is listed in Table 1 and was obtained from the OSHA website.

40

As you can see in Table 1 the TRC rate and the DART rate mirror each other. If the TRC

rate goes up from the previous year so too does the DART rate. Both these rates are reactive loss

or lagging indicators which are after-the-fact measurements that gauge past performance. This

reactive approach provides better administration and temporary relief, but the effort and

investment must continue indefinitely because the root causes of the injuries are never addressed

(EHS Today, 2010). This type of measurement is dependent on incidents to drive their safety

activities and may reflect no more than random fluctuations and is not a valid indicator of safety

improvement (Dial, 1992).

Table 1

Company XYZ’s Performance Trends

Year

TRCR

DART

2007

2006

2005

2004

15.22

17.72

20.33

13.33

12.24

13.97

15.62

11.04

Objective Two

Conduct a review of national aviation accidents statistics to use as a basis for comparison

to Company XYZ. In Table 2 the total recordable case rate is compared for all employees in the

aviation industry for the same time period as Company XYZ. These average industry rates are

for organizations of greater than 1000 employees to have an accurate comparison with Company

XYZ. These rates were all obtained from the Bureau of Labor and Statistics (BLS). Again,

41

these are reactive loss or lagging indicators which are after-the-fact measurements that gauge

past performance.

As you can see in Table 2 the TRC rate and DART rates for the industry average do not

fluctuate as greatly, this is due to the large amounts of data used for the calculation in the

national industry average.

Table 2

Industry Average

Year

1000+ Employees

TRCR

100+ Employees

DART

2007

2006

2005

2004

10.6

10.6

10.3

10.6

8.2

8.5

7.9

8

Table 3 compares the industry average TRCR to Company XYZ’s TRCR for the years of

2004-2007. This side by side comparison clearly shows that Company XYZ is consistently

higher than the industry average for companies of similar size. The TCR considers only incidents

in which workdays were lost and is another reactive measuring tool. As you can see in Table 3,

the industry average for TRC rate stayed relatively flat, where as Company XYZ’s TRC rate

fluctuated considerably.

Incident rates take on more meaning for an employer when the injury and illness

experiences of their firm is compared with that of other employers doing similar work with

42

workforces of similar size (Bureau of Labor and Statistics, 2010). With this side by side

comparison it is easy to see where Company XYZ compares to the industry average.

As you can clearly see between 2004 and 2005 the industry average went down, where as

Company XYZ’s rates jumped considerably. The same holds true for 2005 to 2006 where the

industry average when up but Company XYZ’s average when down.

Table 3

TRCR Comparison

Total Recordable Case Rate

(TRCR)

Year

Industry Average

Company XYZ

2007

2006

2005

2004

10.6

10.6

10.3

10.6

15.22

17.72

20.33

13.33

Table 4 compares the industry average DART rate to Company XYZ’s DART rate for the

years of 2004-2007. The DART rate looks at the amount of time an injured employee is away

from his or her regular job. This side by side comparison clearly shows that Company XYZ is

consistently higher than the industry average for companies of similar size. This table also

shows that Company XYZ has made some improvements; the numbers do not mirror the

industry average. As you can clearly see between 2004 and 2005 the industry average went

down, where as Company XYZ’s rates jumped considerably. The same holds true for 2005 to

2006 where the industry average when up but Company XYZ’s average when down.

43

Table 4

DART Rate Comparison

Days Away Restricted or Transfer

(DART)

Year

Industry Average

Company XYZ

2007

2006

2005

2004

8.2

8.5

7.9

8

12.24

13.97

15.62

11.04

Objective Three

Conduct task analysis of manual material handling activities performed by employees in

height restricted cargo bins at Company XYZ. These qualitative tools consisted of the RULA,

REBA and NIOSH lifting equation. The RULA was used for the on load and off load process of

the male subject in the kneeling position. The REBA was used for the on load and off load

process of the female subject in the erect position. The NIOSH lifting equation was used for

both subjects to determine the lifting indexes for both individuals. The following are the results

of the analysis.

RULA (Rapid Upper Limb Assessment). The RULA Survey was used in determining

the major risk factors of the kneeing position job function. This evaluated the neck, trunk and

legs postures, with a score of greater than 7 for this body posture. The agents knees are directly

on the floor, his legs flexed 90 degrees, his back in an up right neutral position with his body

perpendicular to the front (left) side of the cargo bin. The agent’s arms are up against his trunk

44

in a neutral position. A bag is placed parallel to his body approximately 12 to 14 inches in front

of him with the handle up. With both arms in a neutral position, he extends his right shoulder

and upper arm forward, flexes his elbow approximately 90 degrees, pronates his forearm and in a

pronation hand position uses a power grip to grasp the top handle. He extends his left shoulder

and upper arm forward and down, supinates his left forearm and with a supination hand position

cradles the middle lower part of the bag. The hands, forearms and elbows are in an adducted

position with the trunk in a neutral position. The agents forearm is 14 inches long creating a 4.66

to 1 ratio and generating 233 pounds of upward force. The bag is lifted up approximately 10

inches off the ground parallel to his body. In one motion, he rotates his forearms and wrists

clockwise into a neutral position, with his elbows flexed approximately 90 degrees and brought

back to a neutral position. He twists his trunk clockwise approximately 40% ROM, extends his

shoulders and arms, with extension of his wrists into an ulnar deviated position. His thoracic and

lumbar areas of his back are flexed 15 to 20 degrees, with both elbows slightly abducted. The

bag is now parallel to the floor. As the agent lowers the bag to the floor, he flexes his thoracic

and lumbar areas of his back, he extends his shoulders forward, has full ulnar deviation of both

wrists and both elbows abducted. Once the bag has been set down, both hands release and return

to a neutral position. The thoracic and lumbar areas return to a neutral position along with the

shoulders, upper arms and forearms. This is a repetitive task which occurs approximately 40

times over a 10 minute period.

REBA (Rapid Entire Body Assessment). This assessment was used on the female

employee in the erect position. After the assessment on this job task, the analysis found that this

job is in the “High” risk level (REBA score is 9). The erect body position of this job function

found that both right and left upper arms were in 45 ~ 90 degree flexion position. Also, both

45

right and left lower arms were in between 60 degree to 100 degree flexion. Due to the height of

cargo bin (64 inches), the agent was forced to flex her neck 20 degrees or greater throughout

entire task. Her legs were in a bilateral foot coupling with over 30 degree knee flexion. She did

deviate both her wrists over 15 degrees of flexion/extension. Both shoulders were raised between

a 45 to 90 degrees angle when lifting each baggage. Because of the different styles and shapes of

the baggage, the analysis of this was rated as a fair risk level.

NIOSH Lifting Equation. Using the NIOSH lifting equation the following was

determined:

1. NIOSH lifting equation analysis for the male worker in a kneeling position

i. LC (51LB) * HM (10/13) * VM (1-(.0075*[10-30])) * DM (.82

+ (1.8/36) * AM (1-(.0032*45) * FM (.97) * CM (1.00)

ii. RWL=24.08

iii. Lifting Index = 2.076

2. NIOSH lifting equation analysis for the female worker in a standing position

i. LC (51LB) * HM (10/24) * VM (1-(.0075*[1-30])) * DM (.82

+ (1.8/60) * AM (1-(.0032*45) * FM (.41) * CM (1.00)

ii. RWL= 7.717

iii. Lifting Index = 5.966



Frequency Multiplier (FM), and Coupling Multiplier (CM).

Additional task analysis tools used for objective three were video recording and digital

pictures to analyze various body positions, angles, and rotations. These were measured and

46

determined by using a manual goniometer, digital inclinometer, and hydraulic push-pull

dynamometer. The results of the video and digital analysis are as follows.

Posture. Various postural issues associated with the baggage handling were identified

through visual, video and digital analysis.

Kneel:

o Due to the height of cargo space, the male employee in this study was

forced to kneel both of his knees at 90 degree.

o The kneeling posture without using knee pads places static stress on

male employees’ skeletal and muscular system which can result

injuries such as “Bursa Inflammation”. Bursa inflammation is caused

by repetitive kneeling and crawling on the knees. The bursa or space

between the skin and kneecap becomes inflamed and fills with fluid.

It is a localized injury and does not involve the knee itself.

o Also due to the height of cargo space, female employee in this study

sometimes needs to flex her knees down to reach baggage.

Flexion on neck:

o Due to the height of cargo space, female works was forced to flex her

neck at 20 ~ 30 degrees when performing tasks.

o Constant flexion of female employee’s neck at 20 degrees while

carrying heavy objects compresses her nerves and blood vessels

between neck and shoulder and can result in “Thoracic Outlet

Syndrome.”

47

Flexion on spine:

o Female employee flexes her spine at between 80 ~ 100 degrees to

reach the baggage on the cargo floor. Also, the female employee

constantly flexed her spine about 20 degrees in the confined cargo

space.

o Repetitively flexing the spine can result various back injuries. This

type of posture should be avoided or minimized whenever possible.

Finger press:

o Both male and female employees were placing and packing the

baggage by using either or both hands/finger to press baggage down or

forward.

o Both male and female employees overexert their palms and fingers to

press luggage forward and down. This can cause their synovial sheath

to become swollen, whereby the tendon becomes locked in the sheath.

Eventually, it will cause cumulative trauma disorder like “Trigger

Finger.”

Abduction of both arms:

o In order to reach and pack the baggage, both female and male

employees had both arms abducted between 70 ~ 100 degrees to reach

the luggage.

o Excessive abduction of both arms during the reaching and packing of

the luggage can cause Medial Epicondylitis by overuse of the flexor

muscles.

48

Power Grip:

o This posture was found on both female and male employees.

Unilateral foot coupling:

o This body posture was found only in the female employee. This caused

extra weight to be placed on the right leg and foot.

o Bi-lateral foot posture was found in the video analysis of the female

employee. This type of posture is not suggested due to the extra

amount of weight placed on the leg’s skeletal and muscular system.

Trunk rotation:

o In two of the video clips analyzed, the male worker tended to rotate his

trunk more frequently than the female. This type of posture should be

limited, avoided or greatly minimized.

o High frequency of trunk rotation posture in the male compresses the

spinal disc. Overuse of the trunk muscles is not suggested and should

be avoided or greatly minimized.

Hydraulic Push-Pull Dynamometer. This was used to determine the amount of force

that each employee has to exert to perform the cargo loading task. It was determined that 50

pounds of upward force was needed to lift an average 50 pound piece of luggage. The upward

force generated from length of the forearm was calculated and is as follows.

For the female in a standing position, 183 lbs of upward force is generated from

the equation or a 3.66 to 1 ratio.

For the male in the kneeling position, 230 lbs of upward force is generated from

the equation or a 4.66 to 1 ratio.

49

Posture Repetition. The rate of lifting is approximately 16 times per minute for the

male workers and eight times per minute for the female worker. The average loading time for

entire process is 15 minutes. Therefore, the total time frame for the lifting activity is 240 times

for the male and 80 times for the female.

Table 5 shows the average repetitions of the potential ergonomic postures and

movements as determined from video analysis.

Table 5

One Minute Repetition Average

Repetitions Per Minute

Male Female

Trunk Rotation

Trunk Flexion

Trunk Extension

Finger Press

Abduction

Power Grip

Unilateral Foot Coupling

6

2

4

13

13

15

0

1

10.5

4

8

16

8.5

3.5

Duration of work performed. Each full time employee works four flights per day, with

an average time for each flight being 15 minutes for the loading process. Employees are exposed

to heat and cold stress when performing cargo loading tasks, during the winter months cold stress

can be up to 30 minutes in duration. The average duration at any given point ranges from zero to

15 minutes for these loading tasks. This depends highly on the number of bags that need to be

loaded into the cargo bin; this is the short term duration. Long term duration for a full time

50

employee working four flights per day, 1,000 flights per year, would be moving approximately

39,330 bags one time or 983.25 tons.

Discussion

The results of the methodology used in this study indicate that there are a variety of

ergonomic risk factors the workers are subjected to while performing lifting techniques inside a

height restricted cargo bin. Although Company XYZ does not have the ability to engineer these

risk factors out due to the design of the aircraft, they do have administrative controls in place.

These include training on proper lifting techniques, training on proper stretching techniques, and

a program that requires stretching to be completed prior to each loading event. A discussion of

the REBA and RULA assessment methods and NIOSH lifting equation will demonstrate how the

data from each method closely correlates.

The REBA was performed on the female subject during the loading process from an erect

position. A REBA score of nine was determined by video analysis which correlated with

unilateral foot coupling, neck flexion, back flexion and rotation and adductions of the arms and

shoulders. This score of nine puts these job function movements in a high risk for MSD and

should be investigated further with changes happening soon. Due to bi-lateral foot coupling

fixed or constraint posture is occurring. Splittstoeser, et al., (2007) stated that forces from the

active trunk muscles are the primary determinant of spinal load, increased muscle loading

associated with restricted postures impose increased spinal loading. Fixed or constrained posture

is a body position that overloads muscles and tendons or loads joints in an uneven or

asymmetrical manner, typically from the deviation of the neutral positions of the different body

parts. Like the results of the RULA assessment, Keyserling, et al. (1991) determined that

awkward trunk postures, such as flexion, lateral bending, and twisting, increase the likelihood of

51

back injuries, particularly during lifting. The particular injuries discussed were lower back strains

and sprains.

The RULA was performed on the male subject during the loading process from a

kneeling position. A RULA score of seven was determined by video analysis which directly

correlated with the repetition of back rotation, shoulder abduction during rotation while lifting

heavy objects above the chest and high knee pressure. Shoulders lifting above chest identified

that the arms, elbows, and wrists are at a high risk for developing MSDs due to the abducted arm

postures, and the flexion and extension of the wrists. This score indicates that further

investigation should take place and a change should be made immediately. The risk factors that

have been identified by this assessment method correlate with the information discussed in

Chapter Two of this study by Keyserling, et al. (1991). There is also evidence for a positive

association between highly repetitive work and shoulder MSDs (National Institute for

Occupational Health and Safety, 1997). Repetitive motion is a persistent and continual

movement that can cause localized musculoskeletal injuries or illness. This type of motion is a

large part of the luggage handlers’ duty during the loading process of the cargo bins. Awkward

shoulder postures are a result of the height restrictions these employees face while performing

lifting techniques inside the cargo bins.

The NIOSH lifting equation was performed on both subjects to give a quick

determination of which lifting technique is the least harmful. It was determined that kneeling

was the least detrimental.

This analysis discovered that there are numerous inherent risks involved in lifting inside

the height restricted cargo bins. The most prevalent as determined by the RULA and REBA are

back and neck sprains and strain, and shoulder disorders.

52

Chapter V: Summary, Conclusions and Recommendations



to the limited height in the cargo bins and the restricted posture lifting. The continued presence

of higher than industry average back and shoulder strains and sprains in the height restricted

cargo bins at Company XYZ is placing the organization at risk of incurring continued employee

injury and other workers compensation related forms of loss. Therefore the purpose of this

analysis is to determine the root causes of back injuries sustained during the loading process

inside the height restricted cargo bins. From this root cause analysis an ergonomic solution can

be derived to help reduce the severity of back injuries or ultimately eliminate them. In order to

achieve this purpose, three goals were developed:

1. Conduct an analysis of safety metrics of Company XYZ to better understand their

safety related performance and historical trends.





Methods and Procedures

The methodology used for objective one was the collection of four years of historical

DART and TRC rates. These rates were critical for determining trends with in Company XYZ

and were used for a fair comparison with the industry average. Objective two was to collect the

comparable four years of data as in objective one. This was necessary for a fair comparison

between Company XYZ and the industry average. Once the data from objective one and two

53

had been collected a table was created to show side by side trends for the DART and TCR rates

over the same four years. For objective three the methodology was to collect data through an

initial behavior observation which was conducted over a two week period with out constructive

interactions from the observer. During this observation video and digital photo were taken and

later analyzed to determine flexion, extension, force and foot coupling using a manual

goniometer, digital inclinometer, and hydraulic push-pull dynamometer. Forces applied during

the lifting tasks were measured using a hydraulic push-pull dynamometer. The manual

goniometer used in this study was for the purpose of measuring the total flexion and extension

angles of the back, and the digital inclinometer was used to measure angles of slope and

inclination of an object. Conduct a RULA, and REBA analysis and the NIOSH lifting equation

to record and compare job functions and the types of motions used during the cargo bin loading

process.

The Rapid Upper Limb Assessment (RULA) and the Rapid Entire Body Assessment

(REBA) techniques were performed by observing the participants, and inputting the identified

force and posture angles into the REBA and RULA assessment techniques. The NIOSH lifting

equation was also used to identify, evaluate and classify risks associated with a lifting task.

Although this equation was not designed to assess tasks in a constrained or restricted work space,

it was still performed to help validated the other surveys.

Major Findings

Objective one was a year over year comparison of TRC and DART rates from 2004

through 2007. From the data collect it was found that 2004 was the lowest year for both rates,

the following two years the rates climbed and then began to drop in 2007. Although the rates

began to decline in 2007 the numbers were still significantly higher than the rates of 2004. The

54

results of these numbers indicate that work still needs to be done to determine the specific

reasons for each years rise or decline in rates. For objective two the industry average was

compared to Company XYZ’s TRC and DART rates. The findings from the side by side

comparison show that Company XYZ is significantly higher in both rates and did not follow the

industry trend. These numbers may reflect the fact that Company XYZ operates smaller sized

aircraft with height restricted cargo bins. Object three the RULA Survey was used in

determining the major risk factors of the male employee in the kneeing position job function.

This evaluated the neck, trunk and legs postures, with a score of greater than 7 for this body

posture, which indicates that further investigation is needed and immediate change should be

implemented to minimize upper extremity exposures. The REBA survey was used in

determining the major risk factors of the female employee in the erect position. After the

assessment on this job task, the analysis found that this job is in the “High” risk level (REBA

score is 9), which indicates that the process needs to be investigated, and the process should be

altered. The NIOSH lifting equation was performed on both test subjects while performing their

preferred lifting technique. The male was evaluated in the kneeling position with a RWL of

24.08 and a lifting index of 2.076. The female was evaluated in the standing erect position and

had a RWL of 7.717 and a lifting index of 5.966. The NIOSH Lifting Equation will calculate the

Recommended Weight Limit (RWL) and the Lifting Index (LI). The RWL is the recommended

weight of the load that nearly all healthy workers could lift over a period of time (up to eight

hours) without an increased risk of developing lifting related low back pain or injury, given all

other task parameters remain unchanged. The LI is a relative estimate of the physical stress

associated with a manual lifting job. As the magnitude of the LI increases, the level of the risk

for a given worker increases, and a greater percentage of the workforce is likely to be at risk for

55

developing lifting-related low back pain. From the NIOSH perspective, it is likely that lifting

tasks with a LI > 1.0 pose an increased risk for lifting-related low back pain and injury for some

fraction of the workforce. The NIOSH considers that the goal should be to design all lifting jobs

to achieve a LI of 1.0 or less.

Conclusions

Based on the data collected in this study, the following conclusions can be made about

the workers performing lifting techniques inside the height restricted cargo bins of Company

XYZ:

Reviewing the average DART rate and TRC rate for this industry over a four year

period and comparing that to the average rates of Company XYZ the records revealed

that injuries in the past four years have occurred at a considerable higher rate then the

industry average. This increase in injury occurrence can be attributed to the height

restricted cargo bins at Company XYZ compared to average industry cargo bin

height.

It has been shown that Company XYZ has a higher DART and TCR rate than the

industry average which is also quite high compared to other industries. Therefore I

can conclude that the industry as a whole is suffering higher injury rates due to the

awkward positions needed to perform repetitive lifting during the loading process

inside cargo bins.

The REBA, RULA assessment tools and NIOSH lifting equation used in this study

identified that the current lifting techniques used inside the height restricted cargo

bins are at a high risk for the occurrence of MSD’s. It is concluded from these

56

assessment tools that high repetitive awkward positions are needed for the workers to

perform their job functions inside the height restricted spaces.

Based on the REBA, RULA and NIOSH assessment methods, DART and TRC rates

the risks associated with the current lifting techniques inside the height restricted

cargo bins are repetitive motions, and awkward postures. Through the identification

of past injuries, present risk factors, visual observation, it is possible to conclude that

ergonomic issues are present with the process of proper lifting inside height restricted

cargo bins.

Ulnar deviation does exist in both the kneeling and standing job functions as proven

through video and digital photos.

Trunk and neck flexion exists in both the kneeling and standing job functions as

proven through video and digital photos.

Although there are studies on lifting techniques in height restricted spaces, this

researcher found a very limited amount specific to lifting techniques inside the height

restricted spaces of commercial aircraft cargo bins. From this, one can conclude that

adequate information pertaining to this specific study was not available to compare

this study against.

Recommendations

Based on the conclusions of this study and the hierarchy of controls, the following

control measures are recommended to reduce the exposure of ergonomic-based risk factors and

the occurrence of musculoskeletal disorders while performing lifting techniques inside the height

restricted cargo bins of Company XYZ:

57

Engineering Controls

Since engineering controls for the changes of cargo bin heights are not a viable

option, the total elimination of back and shoulder strains is not attainable through

this method.

Remodeling the height of baggage carts by using hydraulic pressure to adjust the

height of bed of the cart to accommodate 5th ~ 95

th percentile height of workers.

With the ability to raise and lower the height of the cart to accommodate each

individual you will greatly reduce the need for lifting from below the waist,

excessive flexion of the back and provide a better opportunity for two handed

lifts.

Modification to the belt loader to adjust the height levels at which the bags are

brought into the cargo bins. This would allow the loading agents to pick the bag

up at the same height that would be needed to stack the baggage in the cargo bin.

Administrative Controls

Administrative changes can help in the reduction of back and shoulder injuries by

practicing proper lifting techniques and performing stretching exercise before

performing these job functions. Pre and post stretching activities are a proven

method used in the fitness industry to help reduce the chances of muscle sprains

and strains. Supervisor’s would be required to train, monitor and inform

employees that proper stretching exercise can reduce the possibility of injuries.

They will be trained as a trainer and will be required to monitor this on a daily

basis.

58

Proper lifting techniques. Each employee to include management will be trained

on proper lifting techniques, which would include foot position, two handed lifts,

one handed supported lift and lifting from a squatting position. These techniques

will be monitored and enforced by direct supervisors with recurrent training

required yearly.

Routine medical check up’s with an appropriate health care provider. Acquiring

recommendations from the appropriate health care provider regarding existing

and potential risks of injuries can be a proactive approach to preventing serious

injuries.

Job rotation: This method of control is very useful at larger metropolitan airports.

Due to fewer numbers of employees at the Regional Airports, this method may be

not suitable. Regional airport employees perform all job functions and are not

assigned to one specific job.

Task rotation: This method is more likely to have a positive impact on the

reduction of sprains and strains. Rotating the specific tasks performed from

kneeling to standing while loading luggage will help limit specific movements.

Personal Protective Equipment

Personal protective equipment will only be used to help minimize the deviation of

the wrists, the rotation of the trunk and the flexion of the back. This will be

accomplished through the use of knee pads, back belts and wrist splints.

Knee pads: This method of control can reduce the force that is being placed on

both knees. Knee pads also reduce the physical contact between the body and

cargo floor which eliminate temperature extremes (both heat/cold) from

59

contacting with human body. Knee pads can also eliminate cuts from the sharp

edges that form between aluminum cargo floor seams.

Back belt: Although the use of back belts is still controversial. We believe that

back belt will help stabilize and limit the back from twisting. For this reason, we

will still use this method of control to limit the frequency and degree of trunk

rotation from neutral. Employees will wear the back belt only when they are

performing cargo loading or cargo bin tasks.

Wrist Splints: Similar to the back belt. We will use wrist splints only to help

stabilize and limit the frequency of wrist rotation and ulnar deviation. Again, this

type of control will only be use while baggage handling tasks are being

performed.

Recommendations for Further Study

The scope of this study was extremely specific to one aircraft type and the two cargo bins

that are standard in this aircraft. Because of this narrow study other areas of have been identified

for further research. The following areas should be considered for further investigation to

identify the ergonomic-based risk factors that are present:

Determine if PPE recommended for use in this study lowered the severity results in

RULA, REBA and NIOSH lifting equation.

Perform analysis after proper lifting techniques have been taught and are in use with

pre and post stretching activities to determine if lifting techniques have been altered

from this study.

Expand the research to include other aircraft types, and their cargo bins.

60

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