Manual handling is defined by the International Organization for Standardization as any activity requiring the use of human force to lift, lower, carry or otherwise move, or restrain an object, including humans and animals.¹ Manual materials handling (MMH) excludes animate items as objects in such activities. The main risk factors associated with the development of injuries with MMH tasks are forceful exertions, awkward postures, repetitive motions, pressure points, and static postures.² Many different types of jobs or occupations require MMH activities including moving household goods, warehouse handling, truck unloading, inventory restocking, production line loading and unloading, baggage handling, container loading and emptying, transferring material goods, and delivering packages.

Nongovernmental researchers annually examine US Bureau of Labor Statistics (BLS) injury data to ascertain which workplace events caused an employee to miss six or more days of work. Those workplace events are then ranked by total workers’ compensation costs. For the year 2012, the most recent information available, the leading cause of disabling injury was overexertion involving outside sources. This event category includes injuries resulting from lifting, pushing, pulling, holding, carrying, or throwing, all primarily MMH activities. These events cost US businesses $15.1 billion in direct costs and accounted for over 25% of the overall national disabling injury burden.³

In 2011 approximately 3 million workers in private industry and 8 21 000 in state and local government experienced a nonfatal occupational injury or illness with an estimated cost to the US economy of $200 billion annually.⁴ High-risk occupations, which are defined as one where the days-away-from-work (DAFW) rate is at least twice the DAFW rate of 113.3 cases of injury and illnesses per 10 000 full-time employees (FTEs), included two occupations with more than a million workers where MMH activities are involved. These were drivers (sales and trucks) and hand laborers (freight, stock, and material movers).⁴ The estimated number of drivers was 2 721 000 and the DAFW rate was 329.4/10 000 FTE, and for hand laborers the number employed was 1 616 000 and the DAFW rate was 440.3/10 000 FTE.⁴

Musculoskeletal disorders (MSDs), as defined by the BLS, include soft tissue injuries to the trunk and upper and lower extremities and occurred at a rate of 35.8 days-away-from-work cases per 10 000 FTE in 2013 (including private and state and local government).⁵ The MSD rate for transportation and warehousing was 80.3 cases per 10 000 full-time workers which was more than twice the MSD rate for all private industry sectors. MSDs accounted for 33% of all reported illness and injury cases in 2013. Nursing assistants and laborers and freight, stock, and material movers showed the greatest number of MSD cases in 2013.

This chapter provides an overview of the hazards associated with MMH. It will focus on muscular strains and sprains, primarily in the torso or extremities. The prevention of these injuries requires sufficient knowledge to both identify workplace hazards and implement changes in the job or process that will reduce or eliminate these hazards.

OCCUPATIONAL SETTING

MMH poses a risk of injury to many workers; injury is more likely to occur when workers perform tasks that exceed their physical capacities. In addition, the physical capacities of individual workers vary substantially. Because MMH hazards are present in many industrial and service operations, workers in a wide variety of industries are potentially at risk.

The BLS reports that in 2013 there were 1.6 million DAFW cases in private industry and state and local government.⁵ The overall incidence rate of nonfatal occupational injury and illness cases requiring DAFW to recuperate was 109.4 cases per 10 000 FTE. When the BLS data is broken down by body part, the incidence rate for trunk injuries is 26.4 per 10 000 FTE (20.0 for back). The rate for lower extremity (e.g., knee, ankle, foot) is 24.8 and upper extremity (e.g., shoulder, arm, wrist, hand) is 32.5.⁵

A recent report by the National Safety Council indicated that the total number of nonfatal private industry occupational injuries and illnesses involving DAFW was 905 690 cases in 2012.⁶ Overexertion was reported for 3 31 130 cases, and lifting and lowering activities accounted for 106 210 of these cases. On a percentage basis, the parts of the body affected that related to MMH activities were trunk (including the back) (20.4%), upper extremities (shoulder, arm, wrist, hand) (23.9%), lower extremities (knee, ankle, foot, or toe) (18.1%), and neck (1.3%). Transportation and warehousing, the industry sector where MMH activities prevail, had 89 260 nonfatal DAFW cases in 2012. On a percentage basis, the parts of the body affected that related to MMH activities were trunk (including the back) (21.7%), upper extremities (shoulder, arm, wrist, hand) (21.8%), lower extremities (knee, ankle, foot, or toe) (19.5%), and neck (2.1%). The average total workers’ compensation incurred costs per claim for parts of the body associated with MMH activities for 2011–2012 reported by the National Safety Council were as follows: (i) arm/shoulders, $42 742; (ii) lower back, $38 492; (iii) upper back, $34 297; (iv) multiple trunk/abdomen, $22 361; and (v) hand/fingers/wrist, $21 726.⁶ The actual percentage of workers employed in jobs that require MMH tasks is difficult to determine, but three recent surveys of the American workforce indicate that a large percentage of workers are in jobs that require heavy lifting and/or hand movements, which are two indicators of MMH. The three surveys were conducted in 2002, 2006, and 2010 and roughly indicate that 48% of respondents had jobs that required these activities.^7–9

NORMAL ANATOMY AND PHYSIOLOGY OF THE SPINE

The spine is a complex structure made up of bony, muscular, and ligamentous components. The spine can be divided into two major subsystems—the anterior and posterior spine. The anterior spine is mainly composed of the large bony vertebral bodies. These vertebral bodies rest atop one another and are separated by the cartilaginous intervertebral disks, which act as “shock absorbers.” The vertebral bodies and disks are held together by two sets of ligaments. The posterior spine is made up of the additional bony structures of the vertebral peduncles and laminae, which together form the spinal canal. The facet joints, which join two adjacent vertebrae, and the lateral and posterior spinous processes also form part of the posterior spine. The spinous processes are the attachment points for muscles that move and support the spine.

The spine is dependent on both bony and nonbony support for stability. Bony support is provided by the intervertebral disks and the facet joints. Nonbony support comes from the ligaments and the attached musculature. As the bony structures and ligaments do not have enough strength to resist the forces generated during movement and lifting, the spine is dependent on the muscles of the back, abdomen, hip, and pelvis for stability. This principle explains why muscular fatigue is so important in the pathophysiology of back injury. The parts of the spine with the greatest degrees of movement are at highest risk. Because the thoracic and sacral vertebrae are fixed in place by the ribs and the pelvis, the lumbar vertebrae are the most common sites of injury. An excellent compilation of the anatomy and clinical conditions involving the lumbar spine is available in another publication.¹⁰

PATHOPHYSIOLOGY OF INJURY AND RISK FACTORS

The interpretation of the research linking work-related MSDs and MMH is problematic because of the high prevalence of certain disorders in the general population, such as low back pain (LBP), which have a frequent association with nonoccupational factors. In addition, the relationship is further obscured by the wide range of disorders, the nonspecific nature of the condition, and the general lack of objective data relating different risk factors to overexertion injury. In 1997, the National Institute for Occupational Safety and Health (NIOSH) published an extensive review of the epidemiologic literature that assessed the strength of the association between specific work factors and certain upper extremity and lower back MSDs. The NIOSH researchers identified more than 2000 studies, examined more than 600 epidemiologic studies, and published a comprehensive review of the epidemiologic studies of back and upper extremity MSDs and occupational exposures.¹¹

A 2001 report by the National Research Council’s Institute of Medicine summarized a review of the literature on work-related risk factors for low back pain by stating “there is a clear relationship between low back disorders and physical load imposed by manual material handling, frequent bending and twisting, physically heavy work and whole body vibration.”¹² A systematic review conducted by da Costa and Vieira¹³ examined 1761 studies published since the NIOSH¹¹ review on work-related musculoskeletal disorders and concluded that there was reasonable evidence for causal relationship with heavy physical work and MSDs. The most frequently reported risk factors for MSDs were excessive repetition, awkward postures, and heavy lifting, which are activities involved in MMH.¹³

It is generally recognized that musculoskeletal injuries are a function of a complex set of variables, including aspects of job design, work environment, and personal factors. Moreover, work-related MSDs may result from direct trauma, a single exertion (overexertion), or multiple exertions (repetitive trauma); typically, it is difficult to determine the specific nature of the causal mechanism. A variety of manual handling activities increase a worker’s risk of developing an MSD, including jobs that involve a significant amount of manual lifting, pushing, pulling, or carrying and jobs requiring awkward postures, prolonged standing or sitting, or exposure to cyclic loading (whole-body vibration). In addition to these frequent patterns of usage, a variety of personal and environmental factors may affect the risk of developing an MSD. Risk factors increase the probability of occurrence of a disease or disorder, though they are not necessarily causal factors. For the problem of low back injuries involving MMH, four categories of risk factors have been identified by epidemiologic studies—personal, environmental, job related, and psychosocial/organizational:

• Personal risk factors are conditions or characteristics of the worker that affect the probability that an overexertion injury may occur. Personal risk factors include attributes such as age, gender, level of physical conditioning, strength, and medical history.
• Environmental risk factors are conditions or characteristics of the external surroundings that affect the probability that an overexertion injury may occur. Environmental risk factors include attributes such as temperature, lighting, noise, vibration, and friction at the floor.
• Job-related risk factors are conditions or characteristics of the MMH job that affect the probability that an overexertion injury may occur. Job-related risk factors include attributes such as the weight of the load being moved, the location of the load relative to the worker when it is being moved, the size and shape of the object moved, frequency of handling, and the grip forces required to move an object. These factors should be identified because they may be very important for preventing the magnitude of physical hazards to the worker.
• Psychosocial/organizational factors are factors related to the social or organizational environment such as occupational stress, job satisfaction, monotonous work, social support at work, perceived work demands, etc. The mechanisms for how these factors might increase the risk of MSDs is not fully understood, but research shows strong associations with increased physiological and biomechanical responses with MMH activities.^7–9

A tabular presentation of risk factors is provided in Table 3.1.

Work-related MSDs attributed to MMH can result from a direct trauma, a single overexertion, or repetitive loading. It may not always be possible to determine the specific cause of the injury, and the pathology of many types of MSDs is poorly understood. Personal risk factors such as age, fatigue, and concomitant diseases can modify the way the body responds to stressful exertions. Therefore, an injury can occur at different loading levels for different workers. Even for an individual worker, a load may be tolerable one day and excessive on another day due to fluctuations in muscular strength and aerobic fitness.¹⁴

Our knowledge of job-related, environmental, and personal risk factors is far from complete, but more recent research has included a broader range of relevant risk factors in the studies. An important review conducted by Ferguson and Marras¹⁵ led to increased attention to multiple risk factors, highlighting the role that psychosocial factors play in affecting the risk of injury that may be as important as the actual physical demands of the job. The data showed that an increase in perceived job demands coupled with a decrease in workers’ job control and social support led to an increase in physical changes in the worker such as increased muscle tension, lower endurance, and modified body mechanics. Recent systematic reviews^13,16,17 have helped sharpen the focus on which risk factors are the most likely to result inMSDs.

Work-related MSDs are a function of a complex set of variables that include aspects of personal, environmental, job-related, and psychosocial factors. Considerable evidence exists that MMH activities can lead to MSDs, especially to the low back, and MSDs are attributable to numerous risk factors that can be considered in the design of a safe workplace. The interpretation of research findings linking MSDs and MMH is not without problems because of the high prevalence of LBP in the general population and its frequent association with nonoccupational factors. Additionally, significant risk associations can be obscured by a wide range of nonspecific disorders and the general lack of objective data relating different risk factors to overexertion injuries.

MEASUREMENT ISSUES

According to the Occupational Safety and Health Administration (OSHA) a “worksite analysis involves a variety of worksite examinations to identify not only existing hazards, but also conditions and operations in which changes might create hazards. Effective management actively analyzes the work and the worksite, to anticipate and prevent harmful occurrences.”¹⁸ A variety of ergonomic measurement tools are available for the evaluation of MMH tasks, especially manual lifting tasks. These tools range in complexity from simple checklists, which are designed to provide a general indication of the physical stress associated with a particular MMH job, to complicated computer models that provide detailed information about specific risk factors. Excellent reviews have been published summarizing the various methods and tools used in ergonomic assessments that can help in choosing an assessment method that will best fit a worker population.^19–21Table 3.2 summarizes a variety of ergonomic assessment tools and offers a brief description of their advantages and disadvantages.

Ergonomic measurement tools provide objective information about the physical demands of manual handling tasks that will help the user develop an effective prevention strategy. These tools are generally based on scientific studies that relate physical stress to the risk of musculoskeletal injury, particularly when those stressors exceed the physical capacity of the workers.^22–25 Any assessment of physical stress or human capacity is complicated by the influence of a variety of psychosocial factors, including work performance, motivation, expectation, and fatigue tolerance.

Checklists

A checklist is an observational technique that is often the first choice for a rapid ergonomic assessment of a particular workplace. Checklists are designed to provide a general evaluation of the extent of a specific hazard that may be associated with an MMH task or job. A checklist usually consists of a series of questions about physical stressors such as frequent bending, heavy lifting, awkward or constrained postures, poor couplings at the hands or feet, and hazardous environmental conditions. Some checklists use a yes/no format; others use a numerical rating format. Checklists are easy to use, but they lack specificity and they are imprecise. Although there many examples of checklists available, checklists that are more relevant to MMH appear in Appendix B of the NIOSH publication Ergonomic Guidelines for Manual Material Handling.² An example of an MMH checklist is presented in Figure 3.1. For more information on checklists, see David¹⁹, Dempsey et al.²¹, or Eastman Kodak.²⁶

GUIDELINES AND STANDARDS

Early attempts to prevent overexertion injuries associated with MMH focused on adopting arbitrary weight limits for lifting loads, hiring strong workers, or using training procedures that emphasized correct (but not necessarily safe) lifting techniques. None of these approaches, however, have proven to be effective in significantly reducing overexertion injuries.⁶² Recently, industry leaders have started to recognize the risks associated with MMH. To reduce costs and increase productivity, these companies have implemented ergonomic programs or practices aimed at preventing these injuries. In many cases, these ergonomic programs rely on exposure guidelines or standards recommended by the federal government.

The National Institute for Occupational Safety and Health (NIOSH)

NIOSH, the leading federal research agency for ergonomic hazards, does not have a recommended exposure limit (REL) for general MMH activities, but has issued guidelines that can be used for prevention of MMH-related injuries. In 1981, NIOSH published its Work Practices Guide for Manual Lifting (WPG).⁶³ The 1981 WPG contained an equation for assessing certain manual lifting tasks. The 1981 NIOSH lifting equation provided a unique method for determining weight limits for selected two-handed manual lifts, but it was limited in its scope of application. It only applied to lifting tasks that occurred directly in front of the body (sagittal plane lifts) and had optimal hand-to-object couplings (i.e., handles).

Responding to the need for a guideline with a broader application and more flexibility, NIOSH revised the lifting equation. In addition to the four risk factors addressed by the 1981 equation (i.e., horizontal location, vertical height, vertical distance traveled, and frequency), the revised NIOSH lifting equation includes weight reduction factors for the assessment of asymmetric or nonsagittal plane lifts that begin or end to the side of the body and for lifting objects with less than optimal hand-to-object couplings (i.e., no handles).²⁵ The original 1981 NIOSH lifting equation was based on the concept that the overall physical stress for a specific lifting task is a function of the various task-related factors that define the lift, such as task geometry, load weight, and lifting frequency. This concept also forms the basis for the revised NIOSH lifting equation, which provides a practical method for determining the overall physical stress attributable to the various task-related factors.

The revised NIOSH lifting equation yields a unique set of evaluation parameters that include (i) intermediate task-related multipliers that define the extent of physical stress associated with individual task factors; (ii) the NIOSH recommended weight limit (RWL), a task-specific value that defines the load weight that is considered safe for nearly all healthy workers; and (iii) the NIOSH lifting index (LI), which provides a relative estimate of the overall physical stress associated with a specific manual lifting task.

The RWL is defined by the following equation:

where the load constant (LC) is equal to 51 lb and the terms HM, VM, DM, AM, CM, and FM are task-specific multipliers within the equation that serve to reduce the recommended weight limit according to the specific task factor to which each multiplier applies. The magnitude of each multiplier will range in value between zero and one, depending on the value of the task factor to which the multiplier applies. The multipliers are defined as in Table 3.5.

Component	Metric	US customary
HM = horizontal multiplier	(25/H)	(10/H)
VM = vertical multiplier	[1 − (0.003∣V − 75∣)]	[1 − (0.0075∣V − 30∣)]
DM = distance multiplier	[0.82 + (4.5/D)]	[0.82 + (1.8/D)]
AM = asymmetric multiplier	[1 − (0.0032A)]	[1 − (0.0032A)]
FM = frequency multiplier	(Determined from Table 3.6)
CM = coupling multiplier	(Determined from Table 3.7)

In order to use the revised NIOSH lifting equation, you need to make the following measurements:

• L = weight of the load being lifted (lb or kg).
• H = horizontal location of the hands from midpoint between the ankles. Measure at the origin and the destination of the lift (cm or in).
• V = vertical location of the hands above the floor. Measure at the origin and destination of the lift (cm or in).
• D = vertical travel distance between the origin and the destination of the lift (cm or in).
• A = angle of asymmetry, defined as the angular displacement of the load from the sagittal plane when lifts are made to the side of the body. Measure at the origin and destination of the lift (°).
• F = average frequency rate of lifting measured in lifts/minute. Duration is defined as <1, 1–2, or 2–8 hours. Specific recovery allowances are required for each duration category (see Tables 3.6 and 3.7).

Frequency lifts/minute	Work duration
	≤1 hour		≤2 hours		≤8 hours
	V < 75	V ≥ 75	V < 75	V ≥ 75	V < 75	V ≥ 75
0.2	1.00	1.00	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	0.80	0.80	0.60	0.60	0.35	0.35
6	0.75	0.75	0.50	0.50	0.27	0.27
7	0.70	0.70	0.42	0.42	0.22	0.22
8	0.60	0.60	0.35	0.35	0.18	0.18
9	0.52	0.52	0.30	0.30	0.00	0.15
10	0.45	0.45	0.26	0.26	0.00	0.13
11	0.41	0.41	0.00	0.23	0.00	0.00
12	0.37	0.37	0.00	0.21	0.00	0.00
13	0.00	0.34	0.00	0.00	0.00	0.00
14	0.00	0.31	0.00	0.00	0.00	0.00
15	0.00	0.28	0.00	0.00	0.00	0.00
>15	0.00	0.00	0.00	0.00	0.00	0.00

Couplings	Coupling multipliers
	V < 75 cm (30 in.)	V ≥ 75 cm (30 in.)
Good	1.00	1.00
Fair	0.95	1.00
Poor	0.90	0.90

The LI provides 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 to the recommended weight limit. The LI is defined by the following equation:

A detailed explanation of the use of the revised NIOSH lifting equation, including definitions of terms and procedures, is available in an applications manual for the revised NIOSH lifting equation.⁶⁴ The document can be downloaded from the NIOSH website (https://www.cdc.gov/niosh/docs/94-110/).

The developers of the revised NIOSH lifting equation indicated that studies were needed to determine the effectiveness of the NIOSH lifting equation in identifying jobs with increased risk of lifting-related LBP for workers. Researchers at NIOSH published the results of a cross-sectional epidemiologic study designed to evaluate the effectiveness of the equation in identifying jobs with elevated risk of causing LBP.⁶⁵ In the NIOSH study, 50 jobs were evaluated using the revised NIOSH lifting equation. The LI values of the jobs were compared to information obtained about the LBP symptoms in people who worked in those jobs. Using logistic regression modeling, the odds ratio (OR) for LBP was determined for various categories of LI values compared to the unexposed control group. LBP was assessed with a symptom and occupational history questionnaire that was administered to 204 workers employed in lifting jobs and 80 workers employed in nonlifting jobs. Participation was 89–95% among the exposed workers and 82–100% among unexposed workers at four facilities. The authors found that as the LI increased from 1.0 to 3.0, the odds of LBP increased, with a peak and statistically significant OR occurring in the two to three LI category (unadjusted OR = 2.45; CI 1.29–4.85). For jobs with a LI higher than 3.0, however, the OR was lower (1.63; CI 0.66–3.95). The decrease in the OR for these highly exposed jobs is likely to result from a combination of worker selection and a survivor effect. This study also examined several confounding variables such as age, gender, body mass index, and psychosocial factors that were included in the multiple logistic models. The highest OR was in the two to three LI category (2.2; CI 1.01–4.96).

Additional studies conducted in the last decade have broadened the research base that has established the revised NIOSH lifting equation and confirmed its versatility as a valid methodology for estimating LBP risk. For jobs that require multiple MMH activities, a new index methodology has been developed. This method is based on the concept that a composite lifting index (CLI), which represents the collective demands of the job, is equal to the sum of the largest single task lifting index (STLI) and the incremental increases in the CLI as each subsequent task is added. The incremental increase in the CLI for a specific task is defined as the difference between the lifting index for that task at the cumulative frequency and the lifting index for that task at its actual frequency. Other studies have incorporated individual, psychosocial, and work organizational risk factors and their influence on self-reported back pain and the calculation of the lifting index. An excellent article which summarizes this recent research involving the revised NIOSH lifting equation is available from Lu et al.⁶⁶

DIAGNOSIS AND TREATMENT

The primary objectives of the diagnosis and treatment of occupationally related musculoskeletal injuries are to (i) assist the recovery of workers and allow for a rapid return to work (ii) ensure that proper diagnostic tools are used so that an accurate assessment is made of the magnitude of the injury, and (iii) provide appropriate cost-effective treatments that avoid unnecessary surgery. The system should be based on an organized approach to evaluation, diagnosis, and treatment, which is essential for an early return to work and reduction in costs and lost work time. For example, a standardized diagnostic and treatment protocol has been shown to be effective in significantly and continuously reducing the number of incidents, days lost from work, low back surgery cases, and financial costs of LBP.⁶⁷

Although a variety of MSDs result from MMH, the single most costly medical condition is work-related LBP, which affects millions of Americans. Experts have indicated that there is significant variation in assessment and treatment of LBP that results in inappropriate or at least less than optimal care for many patients with low back disorders. This issue was addressed in 1994 with the publication of the Clinical Practice Guideline for Acute Low Back Pain in Adults by the Agency for Health Care Policy and Research (AHCPR).⁶⁸ Copies of the guidelines are available on the agency’s (now renamed the Agency for Healthcare Research and Quality) website at www.ahrq.gov. These guidelines, although somewhat outdated, focused on returning the patient to normal activity and were in widespread use. A more recent review, which is more inclusive and includes additional return to work (RTW) models, is provided by Schultz et al.⁶⁹

Complicating the diagnosis and treatment of occupationally related LBP are the legal issues of disability and compensation and how they relate to pain and impairment. Pain and impairment, which are direct measures of the extent of injury, primarily depend on the severity of the injury. Disability and compensation, however, may depend more on the nature of the compensation system and laws than on the severity of the injury.⁷⁰

MEDICAL SURVEILLANCE

Active and passive surveillance of the workplace are necessary to establish a database of potential exposures in each workplace. Medical management of injuries and early reporting should be incorporated within the general medical treatment program at each work site. Since there is usually a short latency period between exposure and the onset of symptoms, medical surveillance per se is not helpful in eliminating MMH injuries. It may be useful to screen employees in order to match their physical abilities to the job. However, this is more of an exercise in prevention of injuries and is thus covered in the next section on “Prevention.”

PREVENTION

Several strategies have been developed to try and prevent MSD injuries from MMH activities. These strategies can be categorized into three general types: (i) workplace directed, (ii) worker directed, and, (iii) employee screening.

SUMMARY

In summary, MMH activities, such as excessive lifting, pushing, pulling, and carrying, represent a serious hazard for MSD for many workers. There are analytic tools to identify ergonomic hazards that may result in overexertion injury and prevention tools that are effective in reducing the potential for risk of work-related overexertion injury. Successful ergonomic programs require the full cooperation of management, labor organizations, government, and the workers themselves. The solution requires a team effort with a commitment to identify and eliminate hazardous material handling tasks from the workplace.

References

1. 1. International Organization for Standardization. ISO 11228-1:2003. Ergonomics: Manual Handling. Part 1: Lifting and Carrying. Geneva: ISO, 2003.
2. 2. Cal/OSHA Consultation Service and the National Institute for Occupational Safety and Health. Ergonomic Guidelines for Manual Material Handling. DHHS (NIOSH) Publication No. 2007-131. Sacramento/Cincinnati, OH: Department of Industrial Relations/Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, 2007.
3. 3. Liberty Mutual Research Institute for Safety. 2014 Liberty Mutual Workplace Safety Index. Hopkinton, MA: Liberty Mutual Research Institute for Safety, 2014.
4. 4. Centers for Disease Control and Prevention. Nonfatal Work-Related Injuries and Illnesses – United States, 2010. CDC Health Disparities and Inequalities Report—United States, 2013. MMWR 2013; 62 (Suppl 3):35–40.
5. 5. Bureau of Labor Statistics. Nonfatal Occupational Injuries and Illnesses Requiring Days Away From Work, 2013. U.S. Department of Labor, USDL-14-2246, December 16, 2014.
6. 6. National Safety Council. Injury Facts®. Itasca, IL: National Safety Council, 2015.
7. 7. Waters TR, Dick RB, Davis-Barkley J, et al. A cross-sectional study of risk factors for musculoskeletal symptoms in the workplace using data from the general social survey (GSS). J Occup Environ Med 2007; 49(2):172–84.
8. 8. Waters TR, Dick RB, Krieg EF. Trends in work-related musculoskeletal disorders: a comparison of risk factors for symptoms using quality of work life data from the 2002 and 2006 general social survey. J Occup Environ Med 2011; 53(9):1013–24.
9. 9. Dick RD, Lowe BD, Lu M-L, et al. Further trends on work-related musculoskeletal disorders: a comparison of risk factors for symptoms using quality of work life data from the 2002, 2006 and 2010 general social survey. J Occup Environ Med 2015; 57(8):910–28.
10. 10. Bogduk N. Clinical Anatomy of the Lumbar Spine and Sacrum, 5th ed. New York: Elsevier/Churchill Livingstone, 2012.
11. 11. National Institute for Occupational Safety and Health. Musculoskeletal Disorders and Workplace Factors: A Critical Review of Epidemiological Evidence for Work-Related Musculoskeletal Disorders of the Neck, Upper Extremity, and Low Back. DHHS (NIOSH) Publication No. 97-141. Washington, DC: US Department of Health and Human Services, 1997.
12. 12. National Research Council, Institute of Medicine—Panel on Musculoskeletal Disorders and the Workplace, Commission on Behavioral and Social Sciences and Education. Musculoskeletal Disorders and the Workplace: Low Back and Upper Extremities, Washington, DC: National Academy Press, 2001.
13. 13. da Costa BR, Vieira RE. Risk factors for work-related musculoskeletal disorders: a systematic review of recent longitudinal studies. Am J Ind Med 2010; 53:285–323.
14. 14. Pope MH, Frymoyer JW, Andersson G. Occupational Low Back Pain. New York: Praeger, 1984.
15. 15. Ferguson SA, Marras WS. A literature review of low back disorder surveillance measures and risk factors. Clin Biomech 1997; 12(4):211–26.
16. 16. Mayer J, Kraus T, Ochsmann E. Longitudinal evidence for the association between work-related physical exposures and neck and/or shoulder complaints: a systematic review. Int Arch Occup Environ Health 2012; 85:587–603.
17. 17. Gallagher S, Heberger JR. Examining the interaction of force and repetition on musculoskeletal disorder risk: a systematic literature review. Hum Factors 2013; 55(1):108–24.
18. 18. U.S. Department of Labor. Safety and Health Management Systems eTool website. Occupational Safety and Health Administration, http://www.osha.gov/SLTC/etools/safetyhealth/comp2.html accessed August 7, 2015.
19. 19. David GC. Ergonomic methods for assessing exposure to risk factors for work-related musculoskeletal disorders. Occup Med 2005; 55:190–9. doi:1093/occmed/kqi082
20. 20. van der Beek A, Frings-Dresen MHW. Assessment of mechanical exposure in ergonomic epidemiology. Occup Environ Med 1998; 55:190–5.
21. 21. Dempsey PG, McGorry RW, Maynard WS. A survey of tools and methods used by certified professional ergonomists. Appl Ergon; 2005, 36:489–503.
22. 22. Chaffin DB, Park KS. A longitudinal study of low-back pain as associated with occupational weight lifting factors. Am Ind Hyg Assoc J 1973; 34:513–25.
23. 23. Frymoyer JW, Pope MH, Costanza MC, et al. Epidemiologic studies of low back pain. Spine 1980; 5:419–23.
24. 24. Snook SH. The design of manual-handling tasks. Ergonomics 1978; 21:963–85.
25. 25. Waters TR, Putz-Anderson V, Garg A, et al. Revised NIOSH equation for the design and evaluation of manual lifting tasks. Ergonomics 1993; 36(7):749–76.
26. 26. The Eastman Kodak Company. Kodak’s Ergonomic Design for People at Work, 2nd ed. Hoboken, NJ: John Wiley & Sons, Inc., 2004.
27. 27. Ayoub MM, Mital A, Asfour SS, et al. Review, evaluation, and comparison of models for predicting lifting capacity. Hum Factors 1980; 22(3):257–69.
28. 28. Chaffin DB, Andersson GBJ, Martin BJ. Occupa-tional Biomechanics, 4th ed. New York: Wiley-Interscience, 2006.
29. 29. Roderick D, Karwowski W. Manual materials handling. In: Salvendy G, ed. Handbook of Human Factors and Ergonomics, 3rd ed. Hoboken, NJ: John Wiley & Sons, Inc., 2006, pp. 818–54.
30. 30. Chaffin DB, Baker WH. Biomechanical model for analysis of symmetric sagittal plane lifting. AIIE Trans 1970; 2(1):16–27.
31. 31. Schultz AB, Andersson GBJ. Analysis of loads on the lumbar spine. Spine 1981; 6(1):76–82.
32. 32. Freivalds A, Chaffin DB, Garg A, et al. A dynamic biomechanical evaluation of lifting maximum acceptable loads. J Biomech, 1984; 17(4):251–62.
33. 33. McGill SM, Norman RW. Dynamically and statically determined low back moments during lifting, J Biomech 1985; 18(12):877–85.
34. 34. Marras WS Sommerich CM. A three-dimensional motion model of loads on the lumbar spine: I. Model structure. Hum Factors 1991; 33(2):123–37.
35. 35. Marras WS, Sommerich CM. A three-dimensional motion model of Loads on the lumbar spine: II. Model validation. Hum Factors 1991; 33(2):139–49.
36. 36. Marras WS, Allread WG, Burr DL, et al. Prospective validation of a low-back disorder risk model and assessment of ergonomic interventions associated with manual materials handling tasks. Ergonomics 2000; 43(11):1866–86.
37. 37. Kerr MS, Frank JW, Shannon HS, et al. Biomechanical and psychosocial risk factors for low back pain at work. Am J Pub Health 2001; 91(7):1069–75.
38. 38. Skotte JH, Essendrop M, Hansen AF, et al. A dynamic 3D biomechnical evaluation on the load on the low back during different patient-handling tasks. J Biomech 2002; 35:1357–66.
39. 39. Brinckmann P, Johannleweling N, Hilweg D, et al. Fatigue fracture of human lumbar vertebrae: brief report. Clin Biomech 1987; 2(2):94–6.
40. 40. Stevens SS. Mathematics, measurement, and psychophysics. In: Stevens SS, ed. Handbook of Experimental Psychology. New York: John Wiley & Sons, Inc., 1951.
41. 41. Ayoub MM. Psychophysical Basis for Manual Lifting Guidelines. Purchase order number 88-79313, 1988, Preliminary report received 12/16/88. Final report received 2/1/89. Cincinnati, OH: National Institute for Occupational Safety and Health, 1988.
42. 42. Snook SH, Ciriello VM. The design of manual-handling tasks: revised tables of maximum acceptable weights and forces. Ergonomics 1991; 34:1197–213.
43. 43. Ayoub MM, Mital A. Manual Materials Handling. London: Taylor & Francis, 1989.
44. 44. Borg G. Psychophysical scaling with applications in physical work and the perception of exertion. Scand J Work Environ Health 1990; 16(Suppl 1):55–8.
45. 45. Corlett EN, Bishop RP. A technique for assessing postural discomfort. Ergonomics, 1976; 19:175–82.
46. 46. Rodgers SH, Yates JW, Garg A. The Physiological Basis for Manual Lifting Guidelines. Report No. 91-227-330. Springfield, VA: National Technical Information Service, 1991.
47. 47. Garg A. A Metabolic Rate Prediction Model for Manual Materials Handling Jobs. Ann Arbor, MI: University of Michigan, 1976.
48. 48. Astrand PO, Rodahl K. Textbook of Work Physiology, 3rd ed., New York: McGraw-Hill, 1986.
49. 49. Ayoub MM. Determination and Modeling of Lifting Capacity. Final report. Grant no. 5-ROI-OH-00545002. Cincinnati, OH: Department of Health and Human Services, National Institute for Occupational Safety and Health, 1978.
50. 50. Takala EP, Pehkonen I, Forsman M, et al. Systematic evaluation of observational methods assessing biomechanical exposures at work. Scand J Work Environ Health 2010; 36(1):3–24.
51. 51. University of Wisconsin-Madison, Multimedia Video Task Analysis™ (MVTA™). Madison, WI: Ergonomics Analysis and Design Consortium. http://mvta.engr.wisc.edu accessed April 27, 2016.
52. 52. University of Michigan, 3D Static Strength Prediction Program™ (3DSSPP™). Ann Arbor, MI: Center for Ergonomics. http://c4e.engin.umich.edu/tools-services/3dsspp-software/ accessed April 27, 2016.
53. 53. Liu Y, Zhang Z, Chaffin D. Perception and visualization of human information for computer-aided ergonomic analysis. Ergonomics 1997; 40:818–33.
54. 54. Lu M, Waters T, Werren D. Development of human posture simulation method for assessing posture angles and spinal loads. Hum Factors Ergon Manuf Serv Ind 2015; 25(1):123–36.
55. 55. Lowe B. Accuracy of validity of observational estimated of wrist and forearm posture. Ergonomics 2004; 47(5):527–54.
56. 56. Bao S, Howard N, Spielholz P, et al. Interrater reliability of posture observations. Hum Factors 2009; 51(3):292–309.
57. 57. Marras WS, Fattalah F. Accuracy of three dimensional lumbar motion monitor for recording dynamic trunk motion characteristics. Int J Ind Ergon 1992; 9:75–87.
58. 58. Marras WS, Schoenmarklin RW. Wrist motions in industry. Ergonomics 1993; 36:341–51.
59. 59. Grant KA, Galinsky, TL, Johnson PW. Use of the actigraph for objective quantification of hand/wrist activity in repetitive work. In: Proceedings of the Human Factors and Ergonomics Society 37th Annual Meeting, Sheraton Seattle Hotel & Towers/Washington State Convention Center, October 11–15, 1993, Seattle WA. Santa Monica, CA: Human Factors and Ergonomics Society, pp. 720–4.
60. 60. Roetenberg D, Slycke P. Xsens MVN: Full 6 DOF Human Motion Tracking using Miniature Inertial Sensors. Enschede: Xsens Technologies, 2013.
61. 61. Fabers G, Kingma I, Bruijin S, et al. Optimal inertial sensor location for ambulatory measurement of trunk inclination. J Biomech 2009; 42:2406–9.
62. 62. Garg A. What basis exists for training workers in correct lifting technique? In: Marras WS, Karwowski W, Smith JC, et al., eds. The Ergonomics of Manual Work. London: Taylor & Francis, 1993.
63. 63. National Institute for Occupational Safety and Health. Work Practices Guide for Manual Lifting. NIOSH Technical Report No. 81-122. Cincinnati, OH: Department of Health and Human Services, National Institute for Occupational Safety and Health, 1981.
64. 64. Waters TR, Putz-Anderson V, Garg A. Applications Manual for the Revised NIOSH Lifting Equation. DHHS (NIOSH) Publication No. 94-110. Cincinnati, OH: National Institute for Occupational Safety and Health, 1994.
65. 65. Waters TR, Baron SL, Piacitelli LA, et al. Evaluation of the revised NIOSH lifting equation: a cross-sectional epidemiological study. Spine 1999; 24(4):386–95.
66. 66. Lu M-L, Putz-Anderson V, Garg A, et al. Evaluation of the impact of the revised National Institute for Occupational Safety and Health Lifting Equation. Hum Factors 2016; 58(5):667–82.
67. 67. Boden SD, Wiesel SW. Standardized approaches to the diagnosis and treatment of low back pain and multiply operated low back patients. In: Wiesel SW, Wiesel SW, eds. Industrial Low Back Pain: A Comprehensive Approach, 2nd ed. Charlottesville, VA: The Michie Company, 1989.
68. 68. Bigos SJ, Bowyer OR, Braen RG, et al.. Acute Low Back Problems in Adults. Clinical Practice Guideline No. 14. AHCPR Publication No. 95-0642. Rockville, MD: Agency for Health Care Policy and Research, Public Health Service, U.S. Department of Health and Human Services, 1994.
69. 69. Schultz IZ, Stowell AW, Feuerstein M, et al. Models of return to work for musculoskeletal disorders. J Occup Rehabil 2007; 17:327–52.
70. 70. Andersson GBJ, Pope MH, Frymoyer JW, et al.. Epidemiology and cost. In: Pope MH, Andersson GBJ, Frymoyer JW, et al., eds. Occupational Low Back Pain: Assessment, Treatment, and Prevention. St. Louis, MO: Mosby-Year Book, 1991, pp. 95–113.
71. 71. White AA, Gordon SL. Synopsis: workshop on idiopathic low back pain. Spine 1982; 7:141–9.
72. 72. Chou R, Qaseem A, Snow V, et al. Diagnosis and treatment of low back pain: a joint clinical practice guideline from the American College of Physicians and the American Pain Society. Ann Intern Med 2007; 147(7):478–91.
73. 73. Casazza BA. Diagnosis and treatment of acute low back pain. Am Fam Physician 2012; 85(4):343–50.
74. 74. Silverstein BA, Fine U. Evaluation of Upper Extremity and Low Back Cumulative Trauma Disorders: A Screening Manual. Ann Arbor, MI: University of Michigan, School of Public Health, Occupational Health Program, 1984.
75. 75. Frymoyer JW, Haldermans S. Evaluation of the worker with low back pain. In: Pope MH, Andersson GBJ, Frymoyer JW, et al., eds. Occupational Low Back Pain: Assessment, Treatment, and Prevention. St. Louis, MO: Mosby-Year Book, 1991, pp. 151–82.
76. 76. Andersson GBJ, Frymoyer JW. Treatment of the acutely injured worker. In: Pope MH, Andersson GBJ, Frymoyer JW, et al., eds. Occupational Low Back Pain: Assessment, Treatment, and Prevention. St Louis, MO: Mosby-Year Book, 1991, pp. 183–94.
77. 77. Putz-Anderson V. Cumulative Trauma Disorders: A Manual for Musculoskeletal Disorders of the Upper Limbs. London: Taylor & Francis, 1988.
78. 78. Deyo RA. Non-operative treatment of low back disorders. In: Frymoyer JW, ed. The Adult Spine: Principles and Practice. New York: Raven, 1991.
79. 79. Low back disorders. In: Hegmann KT, eds. Occupational Medicine Practice Guidelines. Evaluation and Management of Common Health Problems and Functional Recovery in Workers, 3rd ed. Elk Grove Village, IL: American College of Occupational and Environmental Medicine (ACOEM), 2011, pp. 333–796. http://www.guideline.gov/content.aspx?id=38438 accessed April 27, 2016.
80. 80. Food and Drug Administration. FDA Drug Safety Communication: FDA Requires Label Changes to Warn of Rare but Serious Neurologic Problems after Epidural Corticosteroid Injections for Pain April 23, 2013. http://www.fda.gov/Drugs/DrugSafety/ucm394280.htm accessed April 27, 2016.
81. 81. Machado L, de Souza M, Ferreira P, et al. The McKenzie method for low back pain. Spine 2006, 31(9):254–62.
82. 82. Deyo RA, Loeser JD, Bigos SJ. Herniated lumbar intervertebral disk. Ann Intern Med 1990; 112:598–603.
83. 83. Putz-Anderson V, NIOSH. Ergonomic Solutions for Retailers: Prevention of Material Handling Injuries in the Grocery Sector. DHHS (NIOSH) Publication No. 2015-100. Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, 2014.
84. 84. Occupational Safety and Health Administration. Ergonomics Program Management Guidelines for Meatpacking Plants. OSHA Document No. 3123. Washington, DC: Department of Labor, Occupational Safety and Health Administration, 1990.
85. 85. NIOSH. Workplace Use of Back Belts. DHHS (NIOSH) Publication No. 94-122. Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, 1994.
86. 86. NIOSH. Back Belts: Do They Prevent Injury? DHHS (NIOSH) Publication No. 94-127, Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, 1994.
87. 87. Wassell JT, Gardner LI, Landsittel DP, et al. A prospective study of back belts for prevention of back pain and injury. JAMA 2000; 284(21):2727–32.
88. 88. Bobick TG, Belard J-L, Hsaio H, et al. Physiological effects of back belt wearing during asymmetric lifting. Appl Ergon 2001; 32:541–7.
89. 89. Giocelli RJ, Hughes RE, Wassell JT, et al. The effect of wearing a back belt on spine kinematics during asymmetric lifting of large and small boxes. Spine 2001; 26(16):1794–8.
90. 90. NIOSH. Simple Solutions for Home Building Workers: A Basic Guide for Preventing Manual Material Handling Injuries. DHHS (NIOSH) Publication No. 2013-111. Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, 2013.
91. 91. Robson L, Stephenson C, Schulte P, et al. A Systematic Review of the Effectiveness of Training and Education for the Protection of Workers. DHHS (NIOSH) Publication No. 2010-127. Toronto/Cincinnati, OH: Institute for Work & Health/National Institute for Occupational Safety and Health, 2010.
92. 92. Battíe MC, Bigos SJ, Fisher LD, et al. Isometric lifting strength as a predictor of industrial back pain reports. Spine 1989; 14(8):851–6.
93. 93. Shaw WS, Pransky G, Patterson W, et al. Early disability factors for low back pain assessed at outpatient health clinics. Spine 2005; 30(5):572–80.
94. 94. Kroemer KHE. Testing individual capability to lift material: repeatability of a dynamic test compared with static testing. J Safety Res 1985; 3:4–7.
95. 95. Rothstein JM, Lamb RL, Mayhew TP. Clinical uses of isokinetic measurements. Phys Ther 1987; 67:1840–4.
96. 96. Kroemer KHE. An isoinertial technique to assess individual lifting capacity. Hum Factors 1983; 25:493–506.
97. 97. Kroemer KHE. Matching individuals to the job can reduce manual labor injuries. Occup Safety Health News Dig 1987; 3:4–7.
98. 98. Chaffin DB. Ergonomics guide for the assessment of human static strength. Am Ind Hyg Assoc J 1975; 36:505–11.
99. 99. Herrin GD, Jaraiedi M, Anderson CK. Prediction of overexertion injuries using biomechanical and psychophysical modes. AIHA J 1986; 47:322–30.
100. 100. Herrin GD, Keyserling WM, Chaffin DB, et al. A Comparison of selected work muscle strength. In: Proceeding of the 22nd Annual Meeting of the Human Factors Society, October 1978, Detroit, MI. Santa Monica, CA: Human Factors and Ergonomics Society.
101. 101. Keyserling WM, Herrin GD, Chaffin DB. Isometric strength testing as a means of controlling medical incidents on strenuous jobs. J Occup Med 1980; 22:332–6.
102. 102. Marras WS, McGlothlin JD, McIntyre DR, et al. Dynamic Measures of Low Back Performance: An Ergonomics Guide. Fairfax, VA: American Industrial Hygiene Association, 1993.
103. 103. Bos J, Kuijer PPFM, Frings-Dresen MHW. Definition and assessment of specific occupational demands concerning lifting, pushing, pulling based on systematic literature search. Occup Environ Med 2002; 59:800–6.
104. 104. Marras WS, Cutlip RG, Burt SE, et al. National occupational research agenda (NORA) future direction in occupational musculoskeletal disorder health research, Appl Ergon 2009; 40:15–22.