Ergonomic & Muscular Skeletal Disorder Fact Sheet
Ergonomics is the science of fitting jobs to people. Ergonomics encompasses the body of knowledge about physical abilities and limitations as well as other human characteristics that are relevant to job design. Ergonomic design is the application of this body of knowledge to the design of the workplace (i.e., work tasks, equipment, environment) for safe and efficient use by workers. Good ergonomic design makes the most efficient use of worker capabilities while ensuring that job demands do not exceed those capabilities.
Muscular-Skeletal Disorders
Muscular-Skeletal Disorders are any injury or illness of soft tissues of the upper extremity (fingers through upper arm), shoulders and neck, low back, and lower extremity (hips through toes) that is primarily caused or exacerbated by workplace risk factors, such as sustained and repeated exertions or awkward postures and manipulations. Included are disorders of the muscles, nerves, tendons, ligaments, joints, cartilage and spinal disks. Medical conditions that generally develop gradually over a period of time, and do not typically result from a single instantaneous event. MSDs do not include injuries caused by slip, trips, falls, or other similar accidents. They can differ in severity from mild periodic symptoms to severe chronic and debilitating conditions. Examples of MSDs include:
• Carpal tunnel syndrome
• Tendonitis
• Epicondylitis
• Rotator cuff tendonitis
• Synovitis
• De Quervains’ disease
• Muscle strains
• Carpet layers knee
• Raynaud’s phenomenon
• Trigger finger
• Sciatica
• Low back pain
Signs of Muscular-Skeletal Disorders are objective physical findings. Examples of signs of MSDs include:
• Decreased range of motion
• Swelling
• Decreased grip strength
• Cramping
• Loss of function
• Redness/loss of color
• Deformity
Symptoms of MSDs are physical indications that your employee may be developing an MSD. Symptoms can vary in their severity depending on the amount of exposure the employee has had. Often symptoms appear gradually as muscle fatigue or pain at work that disappears during rest. Usually symptoms become more severe as exposure continues (e.g., tingling continues when your employee is at rest, numbness or pain makes it difficult to perform the job, and finally pain is so severe that the employee is unable to perform physical work activities). Examples of symptoms MSDS include:
• Numbness
• Tingling
• Burning
• Aching
• Pain
• Stiffness
Muscular – Skeletal Disorder (MSD) Risk Factors
Risk hazards consist of numerous elements such as conditions of a job process, work station, or work method. Not all the below listed risk factors will be present in every MSD-producing task, nor is the existence of one of these factors necessarily sufficient to cause a MSD.
• Repetitive and /or prolonged activities
• Forceful exertions
• Prolonged static postures
• Exposure to heat or cold
• Illumination
• Vibration
• Awkward postures, including reaching above the shoulders or behind the back
• Twisting the wrists and other joints.
• Excessive vibration from power tools
• Inappropriate or inadequate hand tools
• Continued bending at the waist
• Continued lifting from below knuckles or above shoulders
• Twisting at the waist, especially while lifting
• Lifting or moving heavy objects
• Lifting or moving asymmetric sized objects
• Prolonged sitting, especially with poor posture
• Lack of adjustable chairs, footrests, body supports, and work surfaces
• Poor grips on handles
• Slippery footing
MSD Hazard Control Methods
Engineering Controls, where feasible, are the preferred method for controlling MSD hazards. Engineering controls are the physical changes to jobs that control exposure to MSD hazards. Engineering controls act on the source of the hazard and control employee exposure to the hazard without relying on the employee to take self-protective action or intervention. Examples of engineering controls for MSD hazards include changing, modifying or redesigning the following:
Workstations
Tools
Facilities
Equipment
Materials
Processes
Work Practice Controls are controls that reduce the likelihood of exposure to MSD hazards through alteration of the manner in which a job or physical work activities are performed. Work practice controls also act on the source of the hazard. However, instead of physical changes to the workstation or equipment, the protection work practice controls provide is based upon the behavior of managers, supervisors and employees to follow proper work methods. Work practice controls include procedures for safe and proper work that are understood and followed by managers, supervisors and employees. Examples of work practice controls for MSD hazards include:
Safe and proper work techniques and procedures that are understood and followed by managers, supervisors and employees.
Conditioning period for new or reassigned employees.
Training in the recognition of MSS hazards and work techniques that can reduce exposure or ease task demands and burdens.
Administrative Controls are procedures and methods, typically instituted by the employer, that significantly reduce daily exposure to MSD hazards by altering the way in which work is performed. Examples of administrative controls for MSD hazards include:
Employee rotation
Job task enlargement
Adjustment of work pace (e.g., slower pace)
Redesign of work methods
Alternative tasks
Rest breaks
Ergonomic Environmental Factors
Heat/Cold: Excessive heat and humidity effects the body’s blood circulation and causes cramps, burns/rashes and general discomfort. Cold exposures also effects the body’s blood circulation and causes hypothermia, loss of flexibility, distraction and poor dexterity. A generally comfortable temperature range is 68 to 74 degrees Fahrenheit – +/-10 degrees depending on the physical work load – with humidity between 20 to 60 percent.
Noise Level/Peaks: Excessive noise levels above 90 decibels (dBA) and noise peaks above 100 decibels (dBA) cause headaches and increases blood pressure, muscle tension and fatigue. High exposure over a long period of time causes deafness and other audiological disorders. Short term exposure causes irritability and distraction.
Illumination: Under-and over-lighted areas causes headaches, muscle strains, fatigue and eye injury. It effects the body by reduced visual acuity, distractions, and glare interference. Poorly lighted areas also provides an atmosphere for trip/fall hazards and poor coordination.
Illumination is measured with a light meter, similar to that used by a photographer. Recommended illumination (measured in foot-candles) by job type:
Job Foot-candles
• General assembly 55 to 150
• Inspections 100 to 150
• Warehouse 50 to 100
• Storage 10 to 50• Offices 100 to 200
Vibration: Excessive vibration causes pain to muscles, joints and internal organs; causes nausea and trauma to the hands, arms, feet and legs. Vibration is measured by its direction, acceleration and frequency on the body.
Environment: Otherwise known as work stress, included in this category are salary administration, job positions, rest breaks, Employee attitude, and boredom. Keeping the Employment Environment up-beat is difficult; however, light colored, well lighted, un-crowded and clean areas provide a positive environment. Employees should rest often depending on their work activity and temperature. Keeping the job moving and variation in activity reduces boredom.
Ergonomic Work Station Design
Using an old rule-of-thumb, if we try to design something that everyone can use, no one will be able to use it. The same principal holds true with ergonomic work station design. The idea of ergonomic work station design is to make it fit the user. It will have to be adjustable for many body heights, sizes, weights and reaches whether sitting or standing.
One of the first principals in Work Station Design is to consider the tallest Employee and the Employee with the shortest reach. The reason being is that we can not shorten an Employee’s height or lengthen an Employee’s reach. Platforms can be used to raise shorter Employees to the proper work height. Either sitting or standing, the Employee should be comfortable at his work station. The arms should rest at the Employees sides and the Employees back/neck should be kept straight; therefore, the work level must be waist-high.
Standing in one place for prolonged periods may lead to a host of injuries. Sit/stand work stations should be considered. If an Employee has to stand, providing something to lean on so the Employee will have the opportunity to rest. Also, providing a heavy rubber pad to stand on will help relieve neck, shoulder, back, and leg stress.
Some common injury prone positions with the body effect are as follows:
| Work Position | Body Effect |
|---|---|
| Standing in one place | Varicose veins, back stress pooling of blood in legs |
| Sitting without back support | Low back stress |
| Chair too high | Decreased circulation, (legs dangling over end) bruises |
| Shoulders rounded | Upper/lower back stress, respiratory distress |
| Leaning forward | Lower back stress |
| Arms extended/over-reaching | Stress to arm muscles, upper back stress |
| Elbows “winged” | Joint stress at shoulder, poor use of bicep muscles |
| Stepping backwards | Loss of balance, displaced gravity, muscle stress |
| Locking knees | Stress to back of knee, poor blood circulation |
With casual observation of work stations, each of these injury prone positions can be eliminated. Almost anytime an Employee has to raise a foot off of the floor to reach a moving or stationary object, they are hyper-extending and are in an injury prone position.
Material Movement
To start, ask this question: “How many times does an Employee have to pick up and carry raw or in-process product before its ready to go out the back door?”. Each time product is moved from one work level to another, the chances of back, neck and shoulder injury and a host of repetitive motion disorders are greatly increased. Conveyor lines, bins and shackle lines should be at the same level as the work station (Approximately waist high). Conveyor lines, carts, trolleys, lifts or other mechanical means should be considered whenever boxes of product are moved from one point to another by an employee. Proper lifting techniques and engineering controls can be used to prevent back injuries.
Ergonomic Tool Design
The last area of work station design is tool design. Many manufacturers are marketing tools that are “ergonomically designed”. However, just because a tool is ergonomically designed, it may do more harm than good. In many cases, just changing the way a toll is used may be and effective solution.
Tools should be designed, modified or used in a manner which allows the hand to rest in a near neutral position. In some cases, heavy tools will need to be suspended from above, so the bulk of the weight is not supported by the Employee’s hands/arm. The handles of the tool should extend the full length of the palm, be soft/shock-resistant and large enough to be easily gripped. Trigger activated tools should be modified to allow multi finger operation which prevents the full required activation force from being applied by only one finger.