Ergonomics: Making the Job Fit
Edition: January 2002 - Vol 10 Number 01
Author: Laura Thill
Ergonomics is more than just a science. It's the meat-and-potatoes of the work environment, be it administrative, health care, manufacturing or something else. All it takes is a chair with no back support, an exam table that fails to permit the physician to move in closely enough to the patient, or a computer with a sticky key and, over a period of time, an employer can be faced with big expenses, both for the cost of medical attention or surgery and the resultant lack of manpower.
Ergonomic-related disorders are among the greatest lost-time injuries in the workplace, notes Lakeside Manufacturing Inc. (Milwaukee, WI). Lakeside cites data from The Penton Institute suggesting that musculoskeletal disorders have tripled in less than a decade and presently account for over 60 percent of all reported illnesses.
With OSHA, NIOSH and various other institutions pressing for the introduction of an ergonomics standard, and the Bush Administration's recent pledge to oversee such a plan, employers must quickly familiarize themselves with design decisions when purchasing equipment and setting up offices. OSHA, in fact, has encouraged employers to identify risk factors that exist in their work environment- a first step toward reducing potential ergonomic dangers and injuries.
What Is Ergonomics?
Ergonomics, according to The Ergonomics Society, is a science of matching the design of tools, systems, equipment and the environment to the needs of the people who use them. It is the process of accommodating the job to the person- not the person to the job. Ergonomics touches upon all aspects of people's lives, from work to sports, leisure, health and safety.
A newer area of study, ergonomics emerged in the late 1940s as an outgrowth of World War II. During the War, systems tended to be designed without completely considering the needs of the user. Over the years, the toll of inefficient design in the work environment became clear.
The Ergonomics Society cites an example where, years back, researchers compared the positions of controls on a lathe to the size of an average male worker. Apparently, the optimum sized lathe operator would have to be 4.5 feet tall, have a shoulder span of two feet, and an arm span of eight feet. Otherwise, the job would require constant stooping and moving from side to side.
It is this repetitive, unnatural motion that leads to musculoskeletal disorders (MSDs). And, as the Brewer Company (Milwaukee, WI) points out, workers with severe MSDs often are unable to return to their jobs or even manage the simplest of tasks, such as combing their hair. Brewer notes that the dental industry alone experiences an annual income loss of $41 million due to musculoskeletal problems. Risk factors in any professional setting can include the following, according to Brewer:
- Repetition. This can range from typing to drilling.
- Awkward posture. Chairs often do not offer substantial back support, or the center of gravity is positioned at the front of the chair, forcing a misalignment of the vertebrae. This, in turn, exerts great pressure on the lower back and legs. In other cases, physicians and other health practitioners spend hours daily bending awkwardly over patients.
- Static posture. This refers to professionals' tendency to spend hours each day sitting.
- Force. This includes pushing, pulling or lifting weight.
- Vibration. Vibrating hand tools, instruments and equipment can cause a condition called ''white finger.''
The ergonomist's job is to study the physical and cognitive abilities and limits of people, including size, vision, hearing, information processing and decision making, according to The Ergonomics Society. Essentially, he or she determines the range of human abilities and relates this information to designers and engineers, ensuring the comfortable use, efficiency and safety of end products, systems and environments.
The ergonomist may also assess products already on the market and determine how they can be improved. Particularly with the capacity to mass produce and mass market, it becomes critical for the ergonomist to point out failures of products to meet the needs of a wide range of users. The Ergonomics Society lists the following areas, among others, that involve the expertise of ergonomists:
- Accidents; health and safety.
- Anatomy, anthropometry, design and biomechanics.
- Cognitive skills and decision making.
- Computer software design and development.
- Design and layout of computer products and terminal workstations.
- Design of controls.
- Design of rooms.
- Environmental conditions (i.e. noise factors, hearing loss, visibility, lighting and vibration).
- Industrial design, medical equipment and user research.
- Commercial workplace design.
- Management and cost-benefit analysis.
- Manual handling, safety and training.
- Office automation.
- Medical and behavioral expectations.
- Product design, sales and marketing.
- Risk assessment.
- Vehicle transport.
There has been much research on the biomechanics of seating and posture, notes Brewer. In research conducted by Marquette University (Milwaukee, WI) and sponsored by Brewer, a 1953 study by Keegan et. al. is cited emphasizing the importance of back support over the lower lumbar spine, an area where most postural back symptoms occur.
A 1975 study by Anderson et. al., supports the need to work in a sitting position to reduce the static effect on leg muscles and limit energy output and demand on blood circulation, says Brewer. But, if the seat fails to support the spine, a condition called kyphosis develops, increasing the load on the lumbar discs, as well as adding more stress to the posterior back structures. A later study in 1979 by Anderson et. al. highlights the importance of lumbar support to the shape of the lumbar curve.
Optimum seating should accomplish the following, according to Brewer:
- Reduce static effects.
- Backrest should support the lumbar region.
- Maintain curvature of the spine.
- Maintain blood circulation.
- Minimize static positions.
When sitting contributes to poor neck flexion, flattening of the spine, or unsupported back, or it positions the center of gravity to the front of the chair, musculoskeletal injuries are likely to occur. Brewer offers the following solutions:
- Seats with a ''no-knob'' adjustable ratcheted backrest.
- Contoured backrest with an adjustable design to support the lumbar strain.
- Synchronized seat tilt and backrest to encourage correct spine curvature.
- Shallow seat pan to help position the lumbar region against the backrest and maintain a pelvic tilt.
- Cut-out seat designed to distribute weight and limit stress on the lower back and thigh area.
- Contoured seat with ''waterfall edges'' designed to maintain circulation at thighs and knees.
Proper seating, says Brewer, permits the comfortable positioning of the neck and full support of the back. The back, too, should be allowed to remain in a natural ''S'' curve position, and the gravity center should be concentrated near the back and center of the seat. The legs ideally should extend at a 90-degree angle.
Ergonomics in Carts
Lakeside Manufacturing agrees that spine, wrist and upper and lower body muscle injuries can occur due to incorrect lifting and pushing. Hence, optimum cart design becomes crucial to safe handling of loads in hospitals and offices. Factors to consider when purchasing a cart include shelf size and carrying capacity. On one hand, purchasers should select the smallest shelf size that can accommodate the intended load. At the same time, the cart capacity must be suited to the heaviest load it might have to carry.
According to Lakeside, ergonomic-oriented cart features include:
- Efficient handle height.
- Angled vertical push handle.
- Shelf placement designed to limit back, knee and arm strain during loading or unloading.
- Wheels and ball bearing casters specially designed to reduce pushing force.
Ergonomic Exam Tables
''One of the biggest problems for physicians and caretakers is back and neck pain,'' notes Dick Moorman, vice president sales, medical products, Midmark Corp. (Versailles, OH). Indeed, it can make a rep ache just to think of a doctor bent over the exam table hour after hour, day after day. It's not only the height of the table that impacts the practitioner, but accessibility to the table as well. How close can the practitioner get to the table? Does the table design permit easy maneuvering around the patient, or does it necessitate constant reaching and straining on the caretaker's end?
Midmark offers the following exam table solutions:
- Low height from the floor to aid obese, disabled and elderly patients in accessing the table.
- Adjustable table height to enable the practitioner to raise the patient, reducing back and neck strain.
- Ergonomical side design. One line of tables offers a 16-inch-wide base and a 27-inch-wide seat, resulting in about six inches of overhang on either side of the table. This allows enough toe and knee space for the practitioner to move in closely to the patient either when standing or sitting.
- Box table design that offers generous toe space, making it easier for the physician to use an otoscope.
- An overhanging back section, tapered for head and neck access, to place the patient more conveniently for the practitioner.
- OB/GYN power table with a drop-down seat to support and position the patient for easier examining.
The University of Virginia/Office of Environmental Health and Safety (UVA/OEHS) offers information on stretch breaks designed to reduce muscle tension and pain from repetitive movements, awkward positioning or excessive force. Exercises focus on the neck, hand, wrist, forearm, shoulder, upper back and arms, and the lower back. For detailed descriptions, please visit the UVA/OEHS website at http://keats.admin.virginia.edu/ergo/stretch.html.