In the context of construction industry, ‘ergonomics’ means: ‘designing the various construction tasks; providing tools, equipment, and materials; and organizing the work to promote worker safety and health’. A practical ergonomics program must approach both the worker as well as the job to match each other. The work methods, equipment and tools design must match the physical and mental capacity of workers, and the environment: noise, temperature, and illumination must be designed to avoid twisting, and bending of body parts. In recent years, there has been a significant increase in the reported cases of ergonomic disorders in the workplace. The Bureau of Labor Statistics [1] reported that the number of disorders associated with repeated trauma nearly doubled in 10 years from 1986 to 1996. The possible causes of this increase can be attributed to the following:

a) A few decades ago, the trades were not strictly bounded - most jobs included a variety of activities: a carpenter, for example, would carry materials and clean the floor. These activities involved footwork and movement of other body parts. With the development of specialty trades concept, trades now use the same body part over and over again resulting in physical fatigue and cumulative trauma of heavily used body part(s).

b) Worker population is aging, and

c) Body parts are getting tired - no job rotation.

Work-Related Musculoskeletal Disorders (WMSDs) are the health disorders arising from repeated stress to the body due to ergonomic hazards or risk factors. WMSDs develop gradually over a period of weeks, months, or years. They include damage to the tendons, bones, muscles, and nerves of the hands, wrists, elbows, shoulders, necks. Backs and legs. Some of the more frequently occurring ergonomic disorders include: low-back pain, carpal tunnel syndrome (CTS), hearing loss, and tendonitis. WMSDs represent 1 in 3 lost time injuries (LTIs) in construction [2]. Characteristics of work-related musculoskeletal disorders (WMSDs) are compared with Occupational Injuries, below:

Work-related musculoskeletal disorders (WMSD) vs. occupational injuries

Work-Related Musculoskeletal Disorders (WMSDs), also called Cumulative Trauma Disorders (CTDs), are the results of cumulative trauma. The occupational injuries, on the other hand, are the result of instantaneous events in the work environment. Figure 1 shows the differences between the occupational injuries and WMSDs. By their very nature, WMSDs when reported pose several problems to the employer, the health care provider, and the insurance company:

Figure 1: Occupational Injury vs. Musculoskeletal Disorder (MSD).

a) They could be fully, or partially psychophysical. Poor worker supervisor relationship, lack of interest (apathy) in work, monotonous or boring jobs, or other job-related frustrations may trigger pains in neck or back.

b) MSDs may not be work-related. They might be the result of other activities at home, in sports, or at other private and uninsured jobs.

c) They can be the result of normal degenerative process of: aging, and/or genetics; or might be the cause of some underlying (preexisting) condition(s).

d) They could be completely non-existent; and might be reported with fraudulent intention, such as: back ache, head ache, etc. Most of such cases cannot be diagnosed instantly and definitively.

e) Occasional ‘pains and aches of life’ can cause MSDs or symptoms of MSDs.

Common WMSDs affecting construction workers

The 1988 Occupational Health Supplement to the National Interview survey [3] compiled data from 30,074 non-institutionalized civilians, the survey statistics show that the construction workers experience about twice the rates of back pain and hand discomfort both due to injury and cumulative trauma, as compared to workers in other industries. In the construction industry, 17.4% of the carpenters, 25.5% of the masons and 19.2% of the roofers suffer from back pain. 20.2% of the carpet layers, 47.5% of steel workers and 23.8% of the plumbers and pipe fitters suffer severe hand discomfort, and 6.7% of the plumbers and pipe fitters and 7.1% of electricians suffer from back pain. Exposure to ergonomic risk factors stresses the affected body parts of the workers and contributes to the development of work-related musculoskeletal disorders (WMSDs). Construction workers are exposed to several risk factors. Identifying the ergonomic risk factors on a worksite is easy with some training and experience and should be done for designing work methods to prevent WMSDs. The following types of ergonomic injuries occur in construction:

• Muscle Pain

• Joint Pain

• Swelling

• Numbness

• Repetitive Stress Injury

• Repetitive Motion Injury

• Restricted Motion

US Navy Public Works Center (PWC Pearl) consulted with the author of this paper, in 1995, to suggest solutions to the increasing number of accidents at their PWC Pearl worksites. The various data on ergonomic injuries presented in this paper, are based on the actual injuries, 1657 in number that occurred at the U.S. Navy work sites. U.S. Navy data included the following items [4]:

• Date of Injury

• Occupation of the injured worker

• Work center

• Body-part affected

• Lost work days

• Medical cost

• Compensation cost, and

• Narrative

This data of 1,657 worksite injuries were organized in a spread sheet and analysed [5]. The narrative of each injury included the task that the injured worker was engaged in at the time of accident, and the type of injury suffered. These descriptions identified the nature of injury: Occupational injury vs. Ergonomic injury. Table 1 shows workcenter wise total occupational injuries, work-related musculoskeletal disorders (WMSDs), and back injuries that occurred at the U.S. Navy worksites. Of the 1657 Occupational injuries, WMSDs totaled 589 (36%), and Back injuries 310 (19%). These percentages match with the construction safety literature which has reported that 33% of the worksite injuries are ergonomic disorders, and 20% are back injuries. Some of the results of the various analyses, performed on this real data, are provided in this paper.

Table 1: Distribution of Total Injuries, WMSDs, and Back Injuries by Work Center (US Navy PWC (Pearl) Database 1987-1994, CSHI 1995a).

Worksite ergonomic risk factors

‘Worksite risk factors’ are defined as: actions in the worksite, worksite conditions, or a combination thereof that may cause or aggravate a work-related musculoskeletal disorder (WMSD). The following worksite risk factors have been known to cause WMSDs [6-9]:

• Repetitive, forceful, or prolonged exertions;

• Frequent or heavy lifting;

• Pushing, pulling, or carrying of heavy objects;

• Fixed or awkward body postures, for prolonged periods;

• Contact stress, or pinch stress;

• Localized or whole-body vibration;

• Cold or hot temperatures;

• Poor lighting (leading to awkward postures); and

• Noise.

These worksite risk factors can be intensified by work organization characteristics, such as:

• Inadequate work-rest cycles,

• Excessive work pace and/or duration,

• Unaccustomed work,

• Lack of task variability,

• Machine-paced work, and

• Piece rate

Signal risk factors

It has been suggested that five specific worksite risk factors have been most closely associated with an increased risk for the development of WMSDs. They have been designated as ‘signal risk factors’. These five signal risk factors include the concept of duration of exposure. It is not the mere presence of a risk factor in the workplace that signals a potential problem, there must be presence for some period. Daily exposure to one of these factors during the work shift is likely to result in a higher risk job. They are screening mechanisms to focus attention on those jobs of greatest concern.

The signal risk factors are:

i Performance of same motion or motion pattern every few seconds for more than two (2) hours at a time;

ii A fixed or awkward work posture for more than a total of two (2) hours;

iii Use of vibrating or impact tools or equipment for more than a total of two (2) hours;

iv Forceful hand exertions for more than a total of two (2) hours; and

v Unassisted frequent or forceful manual lifting.

Table 2 shows the risk factors that caused 589 ergonomic injuries at the U.S. Navy PWC (Pearl) worksites. Manual Materials Handling caused 46% of the WMSDs, followed by Body Postures, which caused 21% of the WMSDs. Together, the two risk factors accounted for 67% of the WMSDs, and both are signal risk factors. Table 2 includes average lost workdays, and average cost per WMSD, caused by the corresponding risk factor.

Table 2: Frequency, Average Lost Workdays, and Average Cost of Each WMSD caused by the corresponding Risk Factor [CSH! 1995a, US Navy PWC (Pearl) Database].

Ergonomic risk factor: Part-of-body relationships

Table 3 shows the effects of risk factors on the parts of a worker’s body. This knowledge can be very useful in planning job rotation to evenly distribute job stress on different body parts.

Table 3: Ergonomic Risk Factor → Part-of-Body Relationship for Construction Workers.

Ergonomic risk factor: WMSD-occupation relationships

Table 4 extracted from several studies reported in the literature, can be used in preventing WMSDs. A causal relationship of this type will relate each of the construction or maintenance activities to WMSDs and can be used in job designs, administrative actions and work methods that would eliminate or reduce WMSDs.

Table 4: Some Example WMSD → Risk Factor → Occupation Relationships in Construction Operations.

During 1992-1994, 90% of disabled older workers, aged 51 to 61 years, had MSDs [10], costing tens of billions of dollars [11], and partially or wholly disabling thousands of construction workers. Prevention of MSDs is therefore important. Ergonomic Risk Controls can be divided in three categories:

1. Engineering Controls

2. Administrative Controls, and

3. Work Practice Controls

Tayyari F et al. [12] have described engineering controls to include: (i) Workstation design to fit all size of workers, (ii) Work method design to minimize: static, awkward and extreme postures; reducing repetitive movements, and excessive forces, (iii) Modifying the strength and endurance requirements of the tasks to be within worker’s mental and physical capacities, and (iv) Ergonomically designing tools and handles to reduce the risk of cumulative trauma disorders (CTDs).

The administrative controls are applied to reduce the duration, frequency and/or severity of exposures to risk factors. Brook A [13] has stated some examples of administrative controls: (i) Provide rest breaks to recover from work induced fatigue, (ii) Increase number of employees assigned to a task, (iii) Use job rotation to insure the same muscle or tendon are not used over and over, (iv) Add various tasks to the employee’s job, and (v) Maintain the equipment and tools.

Several other areas of ergonomic risk controls have been suggested [14]. Surveying the work area to identify potential problems, medical information of the employees, discomfort surveys, absenteeism, and turnover rates are some indicators of job stress. These job stress conditions should be studied, analysed and addressed.

Training and Education to managers and workers are an effective way to show ergonomic risks of their jobs before injuries occur. Written ergonomic safety program that addresses preventive measures, specific to the jobs in progress, can prevent injuries that might lead to CTDs. An example Ergonomics Program is shown in Figure 2.

Figure 2: construction ergonomics program [9].

Identifying problems in a job is the first step and can prevent WMSDs in a cost-effective manner. The identification is a three-step process:

(a) Information for employees

The employer must give each employee exposed to any signal risk factor: information about work-related musculoskeletal disorders (WMSDs). Including their signs and symptoms; the worksite risk factors that can cause or aggravate them; and ways to reduce exposure to the worksite risk factors. The primary purpose of this requirement is to increase employee awareness, giving them the background; they need to recognize illnesses as well as worksite causes so they can effectively participate in the ergonomics program in their work place.

(b) Risk factor checklists

The employer must complete job-specific risk factor checklists to examine employee exposures in the worksite and determine whether there are jobs which must be controlled. Two Risk Factor checklists, one for upper extremities, and the other for back and lower extremities should be completed.

(c) Early reporting of symptoms

It is also important that signs or symptoms of WMSDs be reported early so they can be properly assessed and treated. This may help slow the development of the disorder and speed the healing process. Study of symptoms can also guide in the job method or tools improvement. In order to ensure that this happens, employees must be aware of what symptoms they might experience. They must also know how to report those symptoms and to whom.

In addition, the employer must ensure that no policy or practice that discourages early reporting is established. The design of some incentive programs, safety competitions, or financial incentives may have the effect of discouraging reporting, depending on how they are implemented in the worksites. For example, providing rewards for employees or supervisors when safe work methods are observed would not discourage reporting. However, if employees or supervisors are given financial bonuses if there are no OSHA recordable cases; this may have the unintended but real effect of discouraging reporting of WMSDs.

Medical management of ergonomic injuries can control WMSDs through simple steps shown in Figure 2. The primary goals of medical management are to:

a) Eliminate or reduce musculoskeletal symptoms and conditions associated with work-related risk factors,

b) Eliminate, prevent, or reduce duration and severity of functional impairment from work-related musculoskeletal disorders,

c) Eliminate, prevent, or reduce duration and severity of disability associated with WMSDs,

d) Maintain the morale of the non-injured persons in the group through visible control of the risk factors and boost the pride of the injured person through an efficient return-to-work plan.

A proactive approach in which the employer and the employee work together with the medical practitioner can be effective in returning the injured person to work earlier, in some cases to restricted job assignment.

This paper has identified ergonomic risk factors that cause workrelated musculoskeletal disorders (WMSDs) to construction workers. Based on the real data of 1,657 injuries that occurred at the U.S. Navy Public Works Center (PWC) Pearl, it was found that 589 (36%) of the 1,657 injuries were ergonomic injuries. An analysis of these ergonomic injuries identified the following nine (9) ergonomic risk factors:

i. Frequent or heavy lifting,

ii. Fixed or awkward body postures,

iii. Pushing, pulling, and carrying heavy objects,

iv. Work methods,

v. Hand tools and equipment,

vi. Repetitive, forced, or prolonged exertions,

vii. Noise,

viii. Whole body vibration, and

ix. Personnel relations

This paper has shown the relationship between a risk factor and the part-of-body affected. A table describes the effect of each of the risk factors in causing a work-related musculoskeletal disorder (MSD), and the effect of each of the risk factors on specific construction occupations.

Ergonomic injuries can be eliminated or minimized using three types of risk controls: (i) Engineering controls that include: work station design to fit all size of workers, and work method design to minimize static, extreme, and awkward postures, and to reduce repetitive movements and excessive forces, (ii) Administrative controls to provide rest breaks for recovery from fatigue, and job rotation to avoid using the same body part over and over, etc., and (iii) Work practice controls, such as: keeping tools properly maintained, using low vibration tools, and storing heavy loads at waist height. Several other preventive measures have been mentioned, and a model construction ergonomics program has been suggested.