Ergonomic Risk Factors

What is Ergonomics?

Ergonomics addresses risk with the task, worker, and the environment.
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Ergonomics means finding ways to work easier and just as productive. The goal of the science of ergonomics is to find a best fit between the worker and job conditions. Ergonomics tries to come up with solutions to make sure workers stay safe, comfortable and productive.

Ergonomics also means working smarter, not harder. It looks at the following risk factor categories to see how the job can best fit the worker:

• Risk factors inherent in the worker. Physical, psychological, and non-work-related activities may present unique risk factors.
• Risk factors inherent in the task. Work procedures, equipment, and workstation design may introduce risk factors
• Risk factors inherent in the environment. Physical and psychosocial "climate" may introduce risk factors.

Ergonomic hazards can cause painful and disabling injuries to joints and muscles on a construction site. According to the Occupational Safety and Health Administration (OSHA), ergonomic hazards are the most frequently occurring health hazards in construction and the cause of most injuries.

In a recent survey, 40 percent of construction workers said "working hurt" is a major problem. Working hurt reduces productivity, but continuing to work hurt can result in disabling injuries that end a career. Many laborers retire by age 55 because they just can't do the work anymore. Many can't enjoy their retirement because of their disabilities.

Risk Factors Inherent in the Worker

Age, gender, and strength are all risk factors the worker brings to work.
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Each worker's ability to respond to external demands of a task is different and unique. Studies show that stereotyping or making general assumptions about an employee's ability based on any one of the factors listed below is not correct. The studies described below emphasize the fact that you can't group workers into general categories. Everyone is unique and work needs to be designed to match each employee's unique abilities. The only way to really know what employees are capable of doing is to interview and evaluate them based on the inherent factors listed below:

Age: By the age of 35, most people have had their first episode of back pain. The prevalence of ergonomic injuries increases as people enter their working years. Musculoskeletal impairments are among the most prevalent and symptomatic health problems of middle and old age. However, remember, don't assume all middle- and old-age workers have the same health problems.

Gender: Whether the gender difference seen in some studies of various musculoskeletal disorders (MSDs) is due to physiological differences or differences in exposure is unclear. One study concluded that the lack of workplace accommodation to the range of workers' height and reach may, in part, account for the apparent gender differences. Again, base your determinations on what the worker is capable of doing, not what gender they are.

Physical activity: Some physical activity may cause injury. However, the lack of physical activity may increase susceptibility to injury. We can define "fitness" as combinations of strength, endurance, flexibility, musculoskeletal timing, and coordination. There is clear evidence that stretching exercises do have a positive effect on the reduction of MSDs.

Strength: A worker's strength is important, but not necessarily the key. "Heavy work" stresses the heart and lungs which may result in rapid fatigue - general or localized. The probability of injury increases as muscles weaken. Consequently, demanding repetitive or static muscular work requires energy, not necessarily strength. You may be strong, but not have sufficient energy to do the task.

Anthropometry: Designing for only the "average" person causes problems for everyone else. Anthropometry is the science of studying the difference in body size and proportions by measuring various body characteristics, including weight, physical range of mobility, and body dimensions. This information is then used by designers to engineer tools, equipment, furniture and workstations for maximum efficiency for each individual worker.

The basic ergonomic strategy is to design work based on each worker's unique abilities and not their membership in a general group. Judgment should not be based solely on any one of the above factors. For instance, don't assume that all "old" workers have the same abilities or ergonomic issues. It is important to design work based on the unique factors inherent in each individual, rather than designing work based on generalities.

Risk Factors Inherent in the Task

The task can present many ergonomic hazards.

In addition to considering the worker attributes that may increase the risk of injury, we must also analyze the risk factors the work task itself brings to the job. We look at the task variables in the workplace that may increase or decrease the risk of cumulative trauma disorders (CTDs) depending on its design and location.

In large measure, work processes are determined by the factors below:

Force: Forcefulness is the amount of physical effort required by the person to do a task and/or maintain control of tools and equipment. Examples of work activities that exert force on the body include: lifting, lowering, pushing, pulling, pinching, pounding, hitting, and jumping.

Vibration: Duration of exposure to vibration plays a large role in the effects of vibration forces. There are two basic types of vibration that can result in MSDs:

• Segmental vibration: When handling vibrating tools, such as a jack-hammer, for a prolonged duration, vascular insufficiency in the hand and fingers can also result in interference with sensory receptor feedback. If a worker can't "feel" the grip properly, he or she may compensate by applying more force than is necessary to hold and handle an object. Segmental vibration has also been linked to carpal tunnel syndrome.
• Whole body vibration: When the whole body is subjected to vibration, most commonly experienced by truck drivers, there is an enhanced risk of injury, especially to the lower back.

Risks Factors Inherent in the Task (continued)

Repetitive, forceful movements can cause injuries.

Repetition: Repetition is a measure of how frequently we complete the same motion or exertion during a task. Construction workers nailing shingles, sheetrock, and lumber can suffer from repetitive motion injuries, especially at the wrist. The severity repetitive motion injuries depends on:

• the frequency of repetition,
• speed of the movement or action,
• the number of muscle groups involved, and
• the required force during movement.

Recovery time: Recovery time is a measure of the rest (or low stress activity) period available to the muscle group between similar exertions. Recovery time is important in preventing muscle fatigue because oxygen and metabolites are allowed to rejuvenate while uric acid and other waste products are removed from the muscle group. Recovery time needed will lengthen as the duration of the task increases.

Duration: Duration is a measure of length of time of exposure to a risk factor. Of course, the assumption is that the longer the duration of exposure, the greater the risk of injury. Duration may be measured in seconds, minutes, hours, days, weeks, months, and even years. Food processors handling products while working on conveyor lines may suffer from injuries due to the duration (long hours) of work.

As with most individual risk factors, duration must be considered along with other people, task, and environmental risk factors such as the physical conditioning of the worker, posture, force, weight, temperature, stress, etc.

Risks Factors Inherent in the Task (continued)

Poor posture is a common risk factor in construction.
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Twisting: Twisting in the middle of a lift greatly amplifies the forces on the lower back. The point at which twisting is most likely to cause an injury when lifting objects is in the middle of the lift. Material handling and brickwork are good examples of tasks that require twisting.

Posture: Posture is the position of the body while performing work activities. Awkward posture is a deviation from the ideal working posture of arms at the side of the torso, elbows bent, with the wrists straight. Awkward postures typically include reaching behind, twisting, working overhead, kneeling, forward or backward bending, and squatting. If the posture is awkward during work, there is an increased risk for injury. Food processors repeatedly handling products while working on conveyor lines suffer from repetitive motion issues. The more the joint departs from the neutral position, the greater the likelihood of injury.

Listed below are some specific postures that may be associated with increased risk of injury:

• Extending or flexing the wrist, up and down, regularly is associated with a greater risk of carpal tunnel syndrome.
• Bending the hand toward the little finger regularly greater than 20 degrees increases the risk of pain and other issues.
• Raising the arms which flexes the shoulders greater than 60 degrees for more than one hour a day increases the risk of acute neck and shoulder pain.
• Hands working at or above shoulder level can result in increased risk of tendinitis and various shoulder problems.
• The greater the angle of the neck moves forward, backward or side to side, the more quickly neck and shoulder pain results.
• Bending at the lower back while working increases the likelihood of low back disorders.

Check out this short audio clip by Dan Clark of theSafetyBrief.com that gives 6 tips for good posture on worksites.

Risk Factors Inherent in the Environment

Cold weather increases the likelihood of ergonomic injuries.

Environmental risk factors refer to the physical and psychosocial climate in the workplace include:

• Illumination: Inadequate light can increase the number of attempts in completing a task.
• Sound: Sound can be an irritant to increase stress.
• Humidity: Humidity has an impact on worker endurance which affects the duration with which work can be conducted safely.
• Temperature: Be it too hot or too cold, in combination with any one of the above risk factors may also increase the potential for MSDs to develop.
• Psychosocial: Psychosocial work demands in terms of job control, psychological demands, social support, and job dissatisfaction all can influence the rate at which employees are injured. If your employer forces employees to work fast, not safe, the likelihood of MSDs increases.

Work-Related Musculoskeletal Disorders (MSDs)

MSDs occur when the physical capabilities of the worker do not match the physical requirements of the job. They are caused by job activities and conditions, like lifting heavy objects, repetitive motions, and work in confined areas.

MSDs are common in construction.
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• MSDs are injuries and disorders of the soft tissues (muscles, tendons, ligaments, joints, and cartilage) and nervous system.
• They can affect nearly all tissues, including the nerves and tendon sheaths, and most frequently involve the arms and back.
• MSDs are the leading cause of disability for people in their working years.
• Complaints about back, knee, and shoulder/upper arm are the most prevalent among construction workers.

Studies indicate upper limb and shoulder MSDs were related to manual handling, work repetitiveness, psychosocial demands, job dissatisfaction, gender, and physical unfitness.

Construction workers have an increased risk of these injuries in the following instances:

• when carrying heavy loads
• twisting hands or wrist
• stretching to work overhead
• using certain types of tools
• using vibrating tools or equipment

MSD Injuries and Disorders

Lower Back

When you bend forward, your back muscles work harder and the ligaments flex and stretch. The discs get squeezed. As they are squeezed, they can press on different parts of the spine, including nerves. This can cause back pain. If you bend forward over and over for months or years, the discs are weakened, which may lead to disc rupture (or "herniation").

Twisting your body while bending puts even more pressure on the discs, and more stress on the cartilage and ligaments, especially when you are exerting force to lift, push, or pull objects.

Knee

The muscles in your knees are connected to your leg by tendons. Between the tendons and bones are small sacs of fluid called bursa. They lubricate the knee so it moves easily.

Continual stress on your knee can cause the bursa to get squeezed, swollen, stiff, and inflamed (bursitis). This stress can also cause the knee tendons to become inflamed, resulting in pain (tendinitis).

If you work in a kneeled, stooped position, there is stress on your lower back as well as your knees, possibly leading to back pain and even a serious back injury.

MSD Injuries and Disorders (continued)

Sore necks and shoulders result from bad posture as well as pushing, pulling, lifting, and lowering.

Shoulder

Shoulder pain and injuries are usually the result of overworking the shoulder. When you keep your arm raised above your shoulder (or keep your arm stretched out), your shoulder begins to ache after a short time. It tires easily.

Conditions that result from overuse or continual stress on your shoulder include the following:

• Bursitis - a painful condition that affects the small, fluid-filled "bursae" sacs that cushion the bones, tendons, and muscles
• Tendinitis - inflammation or irritation of a tendon that attaches muscle to bone
• Rotator Cuff Tear - when the tendon partially or completely pulls away from the arm bone

All of these conditions can make routine activities very difficult and painful.

Neck

The neck is a complicated structure composed of seven bones called cervical vertebrae, one below another. It also has cartilage, nerves, muscles, and ligaments. When you keep your neck bent forward or backward, or bend it frequently, the muscles work harder and the ligaments flex and stretch. Eventually the ligaments can partially tear, resulting in neck sprain.

Arms, Hands, and Wrists

Carpal tunnel is a serious repetitive motion disorder.

If you carry heavy objects with hard sharp edges, they can dig into your skin and injure the soft tissues in your hands. Or, if you carry objects that are hard to grip and hold, they may force your hand or wrist into awkward, stressful positions and cause disorders like tendinitis or carpal tunnel syndrome.

Tendinitis

Most of the muscles that move your hand and fingers are actually in your forearm. These muscles are connected to the hand and fingers by tendons, which are like cords passing through your wrist.

You can strain the tendons in your wrist if you frequently exert strong force with your hand, bend your wrist while working, or repeat the same wrist movements over and over. If this strain continues over time, you may develop tendinitis. Tendinitis makes it painful to use your hand, especially to grasp things.

Carpal Tunnel Syndrome

There are 8 small bones in the wrist named carpals. The carpals form a tunnel through which the median nerve and tendons pass through to the hand. If you have tendinitis and your tendons swell, there is less room in the tunnel for the nerve. This causes the median nerve to be pinched causing pain, tingling, or numbness in your hand, wrist, or arm. This condition is called Carpal Tunnel Syndrome.

If left untreated, carpal tunnel syndrome can weaken the hand and make it very difficult to grasp things or even use that hand at all.

Epicondylitis

Forceful twisting motions may cause strain on your elbow tendons, causing discomfort or pain. This condition is called epicondylitis, also known as tennis elbow.

Hand-Arm Vibration Syndrome (HAVS)

This condition is called Renauld's Syndrome or White-Finger Syndrome. Operating vibrating tools like needle guns, chipping hammers, and rotary hammer drills may lead to finger discoloration, tingling, and numbness. Gangrene is possible in the most severe cases.

For more examples of MSDs, click here.

For more information on general ergonomic factors in the workplace, please see OSHAcademy course 711 Introduction to Ergonomics.

Check your Work

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Exercise

For each of the hazards inherent in the tasks mentioned in this module, we gave an example of a task that illustrated the hazard. See if you can match the task with the related hazard we mentioned. There's only one correct answer for each task.