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| Manual materials handling program |
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Step 1: looking for signs of work-related musculoskeletal problems
What are clues or tip-offs to WMSDs as a real or possible workplace problem? Some signs are obvious while others are more subtle. The first step is to look for these signs or clues. |
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- Recognizing signs that may indicate a Problem
- Determining a level of Effort
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Step 2: setting the stage for action
As with other workplace safety and health issues, managers and employees both play key roles in developing and carrying out an MMH/ergonomics program. |
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- MMH/ergonomics as part of a Company Safety & Health Program
- Expressions of Management Commitment
- Benefits and forms of worker Involvement
- Who should participate?
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Step 3: training - building in-house expertise
Identifying and solving workplace WMSD problems require some level of MMH/ergonomics knowledge and skills. Recognizing and filling different training needs is an important step in building an effective program. |
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- MMH/Ergonomics Awareness Training
- Training in Job Analyses and Control Measures
- Training in Problem Solving
- Special Considerations and Precautions
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Step 4: gathering & examining evidence of wmsds
Once a decision has been made to initiate an MMH/ergonomics program, a necessary step is to gather information to determine the scope and characteristics of the problem or potential problem. A variety of techniques and tools have been used; many provide the basis for developing solutions to identified problems. |
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| 1. Health and Medical Indicators |
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- Follow up of worker reports
- Reviewing Statistics and other tracking logs and records
- Conducting symptom surveys
- Using periodic medical examinations
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| 2. Identifying Risk Factors in Jobs |
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- Screening jobs for risk factors
- Performing Job Analyses
- Setting priorities
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Step 5: developing controls
Analyzing jobs to identify factors associated with risks for WMSDs, as discussed in Step 4, lays the groundwork for developing ways to reduce or eliminate MMH/ergonomics risk factors for WMSDs. A variety of approaches can help to control these risk factors. |
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| 1. Types of Controls |
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- Engineering controls
- Administrative controls
- Personal Protective Equipment – Is it effective?
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| 2. Implementing Controls |
| 3. Evaluating Control Effectiveness |
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Step 6: health care management
Company health care management strategies and policies and health care providers can be an important part of the overall MMH/ergonomics program. |
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1. Employer Responsibilities
2. Employee Responsibilities
3. Health Care Provider Responsibilities
4. Issues |
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- Job Familiarity and Job Placement Evaluations
- Early Reporting and Access to Health care Providers
- Treatment
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MMH/ergonomics is the science of adapting work processes and conditions to fit the physical capabilities of workers. The goal is to reduce the incidence of musculoskeletal injuries (MSI) by minimizing or eliminating MSI risk factors.
MSI are injuries of the soft tissues (muscles, joints, tendons, ligaments, cartilage) and nervous system. The most common examples include repetitive strain injuries such as tendinitis and carpal tunnel syndrome, and back injuries involving muscles, ligaments, and/or spinal discs. |
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| Risk factors that increase the likelihood of a worker suffering an MSI include: |
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- Use of excessive force
- Highly repetitive movements
- Awkward and/or static postures
- Manual handling of heavy loads
- Poor tool, equipment, or workplace design
- Poor work organization (lack of task variety, excessive work pace, etc.)
- Cold temperatures
- Vibration
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| Introduction |
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er·go·nom·ics \,ûrg-go-'näm-iks\ - The science of work. MMH/ergonomics removes barriers to quality, productivity and safe human performance by fitting products, tasks, and environments to people.
MMH/ergonomics design is the application of this body of knowledge to the design of tools, machines, systems, tasks, jobs, and environments for safe, comfortable and effective human use" (BCPE, 1993).
The term MMH/ergonomics is derived from the Greek word ergos meaning "work" and nomos meaning "natural laws of" or "study of." The profession has two major branches with considerable overlap. One discipline, sometimes referred to as "industrial MMH/ergonomics," or "occupational biomechanics," concentrates on the physical aspects of work and human capabilities such as force, posture, and repetition. A second branch, sometimes referred to as "human factors," is oriented to the psychological aspects of work such as mental loading and decision-making. |
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| Purpose/Goals of MMH/ergonomics: |
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- occupational injury and illness reduction
- workers' compensation costs containment
- productivity improvement
- work quality improvement
- absenteeism reduction
- government regulation compliance.
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| Methods: |
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- evaluation and control of work site risk factors
- identification and quantification of existing work site risk conditions
- recommendation of engineering and administrative controls to reduce the identified risk conditions
- education of management and workers to risk conditions.
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| Workplace Description |
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| The work setting is characterized by an interaction between the following parameters: |
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- a worker with attributes of size, strength, range of motion, intellect, education, expectations, and other physical/mental capacities.
- a work setting comprised of parts, tools, furniture, control/display panels and other physical objects.
- a work environment created by climate, lighting, noise, vibration, and other atmospheric qualities.
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The interaction of these parameters determines the manner by which a task is performed and the physical demands of the task. For example, a 5' 10", 160-pound, male worker lifts a 35-pound cabinet from the floor by generating 600 pounds of force from the low back muscles.
As the physical demands of a task increase, the risk of injury increases. When the physical demands of a task exceed the physiological capabilities of a worker, an injury will likely occur. |
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| Work Risk Factors |
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| Certain characteristics of the work setting have been associated with injury. These work characteristics are called risk factors and include: |
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- Task Physical Characteristics (primarily interaction between the worker and the work setting)
- Posture
- Force
- Velocity/acceleration
- Repetition
- Duration
- Recovery time
- Heavy dynamic exertion
- Segmental vibration.
- Environmental Characteristics (primarily interaction between the worker and the work environment)
- Heat stress
- Cold stress
- Whole body vibration
- Lighting
- Noise
- Posture
Posture is the position of the body while performing work activities. Awkward posture is associated with an increased risk for injury. It is generally considered that the more a joint deviates from the neutral (natural) position, the greater the risk of injury. Posture issues can be created by work methods (bending and twisting to pick up a box; bending the wrist to assemble a part) or workplace dimensions (extended reach to obtain a part from a bin at a high location; kneeling in the storage bay of an airplane because of confined space while handling luggage).
- Specific postures have been associated with injury. For example:
- Wrist
- Flexion/extension (bending up and down)
- Ulnar/radial deviation (side bending)
- Shoulder
- Abduction/flexion (upper arm positioned out to the side or above shoulder level)
- Hands at or above shoulder height
- Neck (cervical spine)
- flexion/extension or bending the neck forward and to the back
- side bending as when holding a telephone receiver on the shoulder
- Low back
- Bending at the waist, twisting
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| Force |
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Task forces can be viewed as the effect of an exertion on internal body tissues (e.g., compression on a spinal disc from lifting, tension within a muscle/tendon unit from a pinch grasp), or the physical characteristics associated with an object(s) external to the body (e.g., weight of a box, pressure required to activate a tool, pressure necessary to snap two pieces together). Generally, the greater the force, the greater the degree of risk. High force has been associated with risk of injury at the shoulder/neck, the low back, and the forearm/wrist/hand. It is important to note that the relationship between force and degree of injury risk is modified by other work risk factors such as posture, acceleration/velocity, repetition, and duration.
Two examples of the interrelationship of force, posture, acceleration/velocity, repetition and duration are: |
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- A 20-pound weight lifted in a smooth, slow manner one time directly in front of the body from a 28 inch shelf to a 32 inch shelf will be much less of a risk than a 20-pound weight lifted quickly 60 times in 10 minutes from the floor to a 60 inch shelf.
- A 45-degree neck flexion position held for one minute will be much less of a risk that a 45-degree neck flexion position held for 30 minutes.
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Better analysis tools (e.g., 1991 Revised NIOSH Lifting Equation) recognize the interrelationship of force with other risk factors relative to overall task risk.
Five additional force-related injury risk conditions have been extensively studied by researchers and ergonomists. They are not "rudimentary" risk factors. Rather, they are a workplace condition that presents a combination of risk factors with force being a significant component. Their common appearance in the workplace and strong association with injury prompts their introduction here. |
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Static Exertion
Although defined in a variety of ways, static exertion generally means the performance of a task from one postural position for an extended duration. The condition is a combination of force, posture, and duration. The degree of risk is in proportion to the combination of the magnitude of the external resistance, awkwardness of the posture, and duration.
Grip
A grip is the conformity of the hand to an object accompanied by the application of exertion usually to manipulate the object. Hence, it is the combination of a force with a posture. Grips are applied to tools, parts, and other physical objects in the work setting during task performance.
To generate a specific force, a pinch grip requires a much greater muscle exertion than a power grip (object in the palm of the hand). Hence, a pinch grip has a greater likelihood of creating injury.
The relationship between the size of the hand and the size of the object also influences risk of injury. |
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| Contact Trauma |
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| Two types of contact trauma are: |
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- local mechanical stress generated from sustained contact between the body and an external object such as the forearm against the edge of a counter.
- local mechanical stress generated from shock impact such as using the hand to strike an object.
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| The degree of injury risk is in proportion to the magnitude of force, duration of contact, and sharpness of external object. |
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Gloves
Depending on material, gloves may affect the grip force generated by a worker for a given level of muscular exertion. To achieve a certain grip force while wearing gloves, a worker may need to generate greater muscular exertion than when not wearing gloves. Greater force is associated with increased risk of injury.
Bulky Clothes
Bulky clothes, used to protect the worker from cold or other physical elements, may increase the muscle effort required to perform tasks.
Velocity/Acceleration
Angular velocity/angular acceleration is the speed of body part motion and the rate of change of speed of body part motion, respectively.
Repetition
Repetition is the time quantification of a similar exertion performed during a task. A warehouse worker may lift and place on the floor three boxes per minute; an assembly worker may produce 20 units per hour. Repetitive motion has been associated with injury and worker discomfort. Generally, the greater the number of repetitions, the greater the degree of risk. However, the relationship between repetition and degree of injury risk is modified by other risk factors such as force, posture, duration, and recovery time. No specific repetition threshold value (cycles/unit of time, movements/unit of time) is associated with injury.
Duration
Duration is the time quantification of exposure to a risk factor. Duration can be viewed as the minutes or hours per day the worker is exposed to a risk. Duration also can be viewed as the years of exposure to a risk factor or a job characterized by a risk factor. In general, the greater the duration of exposure to a risk factor, the greater the degree of risk.
Duration limits for risk factors that can not be isolated (e.g., force/repetition/posture during small assembly task) have not been established.
Recovery time
Recovery time is time quantification of rest, performance of low stress activity, or performance of an activity that allows a strained body area to rest.
Short work pauses have reduced perceived discomfort and rest periods between exertions have reduced performance decrement.
The recovery time needed to reduce the risk of injury increases as the duration of risk factor increases. Specific minimum recovery times for risk factors have not been established.
Heavy dynamic exertion
The cardiovascular system provides oxygen and metabolites to muscle tissue. Some tasks require long-term/repetitive muscle contraction such as walking great distances, heavy carrying, and repeat lifting.
As physical activity increases, muscles demand more oxygen and metabolites. The body responds by increasing the breathing rate and heart rate.
When muscle demand for metabolites cannot be met (metabolic energy expenditure rate exceeds the body's energy producing and lactic acid removal rate) physical fatigue occurs.
When this happens in a specific area of the body (shoulder muscle from repeat or long term shoulder abduction), it is termed localized fatigue and is characterized by tired/sore muscles.
When this happens to the body in general (from long-term heavy carrying/lifting/climbing stairs), it is termed whole body fatigue and may produce a cardiovascular accident.
Also, high heat from the environment can cause an increase in heart rate through body cooling mechanisms. Therefore, for a given task, metabolic stress can be influenced by environmental heat.
Exercise to strengthen your back and reduce stress
Having strong back and stomach muscles is important in order to ease the work your back is put through each day. By doing simple back-toning exercises, you not only strengthen your back but also reduce stress and improve your appearance, too! Check with your doctor as to the best exercises for you.
Lose excess weight
Pot bellies and excess weight exert extra force on back and stomach muscles. Your back tries to support the weight out in front by swaying backwards, causing excess strain on the lower back muscles. By losing weight, you can reduce strain and pain in your back. Check with your doctor for the most sensible diet plan for you
Maintain good posture
You can prevent many back pains by learning to sit, stand and lift items correctly. When you sit down, don't slouch. Slouching makes the back ligaments, not the muscles, stretch and hurt, thus putting pressure on the vertebrae. The best way to sit is straight, with your back against the back of the chair with your feet flat on the floor and your knees slightly higher than your hips. Learn to stand tall with your head up and shoulders back.
Maintain good posture while you sleep and drive
Sleep on a firm mattress or place plywood between your box springs and mattress for good back support. If your mattress is too soft it could result in a back sprain or sway back. Sleep on your side with your knees bent or on your back with a pillow under your knees for support. Drive with your back straight against the seat and close enough to the wheel so your knees are bent and are slightly higher than your hips.
Plan your lift
Lifting objects is often a mindless task, and unfortunately many people perform their lift incorrectly, resulting in unnecessary strain on their back and surrounding muscles. In order to lift correctly and reduce strain on your back, it's important to plan your lift in advance. This means to think about the weight of the object you will be moving and the distance you will be moving it. Is it bulky? Will you need help? Do you see any hazards that can be eliminated? Think about this whenever you do any lifting.
Position yourself correctly in front of the load
Once you have planned your lift, the next important step is to align yourself correctly in front of the load with your feet straddling the load, one foot slightly in front of the other for balance. Slowly squat down by bending your knees, not your back and stomach. Using both hands, firmly grab the load and bring it as close to your body as you can. This will help distribute the weight of the load over your feet and make the move easier.
Lift with your legs, not your back
Once the load is close to your body, slowly straighten out your legs until you are standing upright. Make sure the load isn't blocking your vision as you begin to walk slowly to your destination. If you need to turn to the side, turn by moving your feet around and not by twisting at your stomach.
Set the load down correctly
Once you have reached your destination, it's equally important that the load is set down correctly. By reversing the above lifting procedures you can reduce the strain on your back and stomach muscles. If you set your load on the ground, squat down by bending your knees and position the load out in front of you. If the load is set down at table height, set the load down slowly and maintain your contact with it until you are sure the load is secure and will not fall when you leave.
Get help, if needed
If the load is too heavy, bulky or awkward for you to lift alone, find a friend to help you carry it. If no one is available, is it possible to break the load into two smaller loads? Or, can you locate a cart or dolly to help you move it? Look for simple solutions to help make the move easier on you and your back. |
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