Human engineering

Alexander technique, Bernardino Ramazinni, Blackberry thumb, carpal tunnel, carpal tunnel syndrome, cognitive ergonomics, ergon, ergonomics, ergonomists, human engineering, human factors, immediate reach zone, MSD, musculoskeletal disorders, nomoi, organizational ergonomics, physical ergonomics, posture, repetitive stress injury, RSI, tendonitis, Wojciech Jastrzebowski, work related upper limb disorder, WRULD.

Ergonomics is a discipline that involves arranging the environment to fit the person in it. Ergonomics, also called human factors or human engineering, is the scientific discipline concerned with the understanding of interactions among humans and other elements of a system.When ergonomics is applied correctly in the work environment, visual and musculoskeletal discomfort and fatigue are reduced significantly.

As a profession, ergonomics applies theory, principles, data, and methods to design in order to optimize human well-being and overall system performance.

Italian Bernardino Ramazinni (1633-1714) became the first physician to write about work-related injuries and illnesses in his 1700 publication, De Morbis Artificum (Diseases of Workers). Ramazinni was ostracized by his fellow doctors for visiting the workplaces of his patients in order to identify the causes of their disorders. The term ergonomics has its origin in the Greek words ergon (work) and nomos (natural laws) first entered the modern dictionary when Wojciech Jastrzebowski used the word in his 1857 article.

Ergonomists have attempted to define postures, which minimize unnecessary static work and reduce the forces acting on the body. Therefore, adherence to the ergonomic principles may significantly reduce the risk of injury due to repetitive movements. There are many computer-related "ergonomic" products, the most common ones being: "ergonomic" keyboards, "ergonomic" mice, wrist rests, support braces/gloves, and forearm supports/resting forearms on chair arms.

One of the primary goals of ergonomics is prevention of workplace illness and accidents. According to the United States Bureau of Labor Statistics, more than 60% of the workplace illnesses reported each year are associated with repetitive stress injuries (RSI). These injuries result from continuous repetition of the same motions, for instance screwing or twisting items on an assembly line. The injury may be exacerbated by awkward postures, such as bending or reaching too often.

Repetitive stress injuries include carpal tunnel syndrome, tendonitis, and Blackberry thumb. The Centers for Disease Control and Prevention (CDC) currently recommends the integration of ergonomics in the workplace in order to reduce the prevalence of repetitive stress injuries.

Ergonomists view people and the objects they use as one unit, and ergonomic design blends the best abilities of people and machines. Humans are not as strong as machines, nor can they calculate as quickly and accurately as computers. Unlike machines, humans need to sleep, and they are subject to illness, accidents, or making mistakes when working without adequate rest. Nevertheless, machines are also limited - cars cannot repair themselves, computers do not speak or hear as well as people do, and machines cannot adapt to unexpected situations as well as humans. An ergonomically designed system provides optimum performance because it takes advantage of the strengths and weaknesses of both its human and machine components.

Understanding human limitations early in the development of medical devices can reduce errors and avoid performance problems exacerbated by stress and fatigue. Using ergonomics in a design process may reduce the costs of procuring and maintaining products. It may also minimize the incidence of injury or longer-term malaise from poor working environments.

Many ergonomic problems associated with computer workstations occur in the shoulder, elbow, forearm, wrist, and hand. Continuous work on the computer may expose soft tissues in these areas to repetition, awkward postures, and forceful exertions, especially if the workstation is not set up properly. For example, the mouse device is present in virtually every office environment and designed specifically to the contours of either the right or left hand. Placing the mouse, trackball, or other input device too far away, too low, or too much on one side can cause shoulder, wrist, elbow, and forearm discomfort; however, they offer natural comfort and maximum hand-to-eye coordination when placed within the immediate reach zone.

The Office of Health and Safety at the Center for Disease Control (CDC) has identified repetitive motion injuries as a factor in employee injuries. Repetitive stress injury, also called repetitive strain injury, is an injury caused by overuse of muscles, tendons, and nerves. Usually, it affects the muscles, tendons, and nerves in the arms and upper back; hence it is also known as work related upper limb disorder (WRULD). The medically accepted reason it occurs is when muscles in these areas are kept tense for very long periods of time, due to poor posture and/or repetitive motions. It is most common among assembly line and computer workers. Good posture and ergonomic working conditions may help prevent or halt the progress of the disorder; stretches, strengthening exercises, and massages training to reduce neck and shoulder muscle tension can help heal existing disorders.

One prime example of a repetitive strain injury is carpal tunnel syndrome, which is a painful and often debilitating swelling of the tendons in the wrist. Carpal tunnel results from overuse of the hands and wrists. It is particularly common in people who must bend or overextend their arms while performing a repetitive task, such as typing on a computer keyboard, cutting meat, or tripping knobs and levers.

Rempel et al (2006) conducted a randomized controlled intervention trial to assess body pain severity and incident musculoskeletal disorders among 182 call center operators at a large healthcare company for one year. Participants were randomized to receive (1) ergonomics training only, (2) training plus a trackball, (3) training plus a forearm support, or (4) training plus a trackball and forearm support. Outcome measures were weekly pain severity scores and diagnosis of incident musculoskeletal disorder in the upper extremities or the neck/shoulder region based on physical examination performed by a physician blinded to intervention. The study reported 63 participants diagnosed with one or more incident musculoskeletal disorders. Hazard rate ratios showed a protective effect of the armboard for neck/shoulder disorders (HR = 0.49, 95% CI 0.24 to 0.97) after adjusting for baseline pain levels and demographic and psychosocial factors. The armboard also significantly reduced neck/shoulder pain (p=0.01) and right upper extremity pain (p=0.002) in comparison to the control group. The investigators concluded that providing a large forearm support combined with ergonomic training is an effective intervention to prevent upper body musculoskeletal disorders and reduce upper body pain associated with computer work among call center employees.

The availability of higher quality studies investigating ergonomic interventions to prevent or limit musculoskeletal disorders is limited. No well-known single intervention is universally effective. For example, there is no consistent research evidence that wearing wrist supports during computer use actually helps reduce the risk of injury, or is cost effective. Successful interventions require attention to individual, organizational, and job characteristics, tailoring the corrective ergonomic actions to those characteristics.

This information has been edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

Centers for Disease Control and Prevention. 7 July 2006.

Ergonomics.org. 7 July 2006.

Rempel DM, Krause N, Goldberg R, et al. A randomised controlled trial evaluating the effects of two workstation interventions on upper body pain and incident musculoskeletal disorders among computer operators. Occup Environ Med. 2006 May;63(5):300-6.

Schneider S. National Academy of Sciences Workshop and Report on the Science of Ergonomics. Appl Occup Environ Hyg. 1999 Feb;14(2):75-7.

Schneider S. The year 2000 in ergonomics. Appl Occup Environ Hyg. 2001 Apr;16(4):432-7.

Stone R, McCloy R. Ergonomics in medicine and surgery. BMJ. 2004 May 8;328(7448):1115-8.

Ergonomists draw on the principles of their environment, industrial engineering, psychology, anthropometry (the science of human measurement), and biomechanics (the study of muscular activity), physiology, psychology, and kinesiology to adapt the design of products and workplaces to people's sizes and shapes a well as their physical strengths and limitations. In doing so, the safety, comfort, and efficiency of the products in the workspace are maximized when used by individuals. Ergonomists also consider the speed with which humans react and how they process information, and their capacities for dealing with psychological factors. Armed with this complete picture of how humans interact with their environment, ergonomists develop the best possible design for products and systems, ranging from the handle of a toothbrush to the flight deck of the space shuttle. An ergonomics task analysis can also help identify key components of surgical skill, ensuring that students have affordable, appropriate, valid, and reliable training.

The International Ergonomics Association (IEA) divides ergonomics into three domains, which deal with different aspects of ergonomics.

Physical ergonomics deals with the human body's responses to physical and physiological loads. Relevant topics include workstation layout, job demands, and risk factors such as repetition, vibration, force, and awkward/static posture as they relate to musculoskeletal disorders.

Cognitive ergonomics, also known as engineering psychology, concerns mental processes such as perception, attention, cognition, motor control, and memory storage and retrieval as they affect interactions among humans and other elements of a system. Relevant topics include mental workload, vigilance, decision-making, skilled performance, human error, human-computer interaction, and training.

Organizational ergonomics, or macroergonomics, is concerned with the optimization of sociotechnical systems within a workspace, including their organizational structures, policies, and processes. Relevant topics include shift work, scheduling, job satisfaction, motivational theory, supervision, teamwork, telework and ethics.

One training program that cultivates ergonomic skills is the Alexander technique. It has a long history of helping people develop the subtle coordination of thought and physical action required to monitor and alter harmful patterns of posture and movement. In short, it enables individuals to put ergonomic principles into practice, and thus helps them reduce their risk of developing a repetitive strain injury.

Most ergonomists concerned with physical ergonomics in a work environment agree that it is a good idea to take frequent, brief rest breaks. The below list are example of ergonomic recommendations.

Eye breaks: Looking at a computer screen for long periods of time may cause changes in how the eyes work, blinking frequency and exposure of the eye surface to air. Many experts recommend looking away from the computer screen every 15 minutes for a minute or two to a more distant scene, preferably something more that 20 feet away. This lets the muscles inside the eye relax. Blinking the eyes rapidly for a few seconds refreshes the tear film and clears dust from the eye surface.

Micro-breaks: Most typing is done in bursts rather than continuously. Between these bursts of activity, the hands can be rested in a relaxed, flat, straight posture. During a micro-break (<2 minutes) an individual can briefly stretch, stand up, move around, or do a different work task (e.g. make a phone call). A micro-break is not necessarily a break from work, but it is a break from the use of a particular set of muscles that is doing most of the work (e.g. the finger flexors if typing).

Rest breaks: Every 30 to 60 minutes a rest break is recommended. During this break stand up, move around and do something else. Such breaks allow an individual to rest and exercise different muscles, with the result of feeling less tired.

Exercise breaks: There are many stretching and gentle exercises that an individual can do to help relieve muscle fatigue; these are recommended every 1-2 hours.

Ergonomic software: Ergonomic software is available that can prompt users to take a rest break at appropriate intervals, and suggest simple exercises.

Ergonomic products: Ergogenic mice are popularly used; however, it may be important to note that these be used with the upper arm relaxed and as close to the body as possible. It is thought that overreaching to an "ergonomic mouse" defeats any benefits of this design. Wrist pads have also been commonly used. Though these products were very popular a few years ago, research studies have not demonstrated any substantial benefits for wrist rests. In fact, a wrist rest may increase pressure inside the carpal tunnel by compressing the undersurface of the wrist. Wrist supports that wrap around the wrists may also be used, but evidence is lacking as to its effectiveness. Those that choose to wear these are advised by experts to keep the hands flat and straight, not bent upwards. Ergonomic products are commonly available for purchase at most office supply stores.

Forearm supports/resting forearms on chair arms: Current opinion does not recommend resting the forearms on any support while typing because of the potential for restriction of circulation to the finger flexor muscles in the forearm and compression of the ulnar nerve at the elbow. If forearm supports are required it is usually a sign of a poor ergonomic arrangement. If the keyboard/mouse are appropriately arranged they should be accessible with the user's arms in a neutral position (close by the body and with the upper arm hanging in a relaxed way) which does not pose any significant neck or shoulder load.

Sit-stand workstations: The use of a height adjustable work surface for sitting and standing work is also popular. An individual can alternate between sitting and standing positions to modify the height of the work surface throughout the day. Such workstations may reduce musculoskeletal discomfort and improve work performance.

Height adjustable, split work surfaces: Similarly, split work and height adjustable surfaces are primarily designed to aid with wrist posture: