Throughout 2011, Louise Lynch and Roy Matheson & Associates, will be presenting a series of WorkSafe webinars intended to give a sneak peek at the online software, while at the same time giving helpful knowledge and resources about ergonomic evaluation and workplace risk factor assessment.
This series will focus on how to use Matheson Resolutions Services new online Ergonomic Software to bring new revenue into your business. Webinars will be held on the third Thursday of every month from 3:30-4:45 p.m. EST (GMT-5).
Coming up, on January 20th, is the inaugural webinar:
How WorkSafe Solves Ergonomic Issues
This one hour webinar will give an overview of why the software was developed, it's ease of use and most importantly how it will allow you to bring in new business with local employers who have soft tissue injuries in their workplace. Those who have mobile devices are encouraged to have them available to find out how easy it is to solve ergonomic issues while at the workplace.
Check out the schedule for the rest of 2011 on our website!
(Links to register for future months will be added during the month in which the webinar takes place.)
We hope to see you there!
In Part I of this series, we discussed the risk factors of Magnitude, Repetition, Duration and Force. In Part II of II, we will be discussing: Posture and Motion, Vibration, Cold Temperatures, Work Organization and Psychosocial & Psychophysical factors.
Posture and Motion
Posture angles are measured in terms of the number of degrees a specific joint deviates from neutral.
Body landmarks for measuring angles are described in the American Academy of Orthopedic Surgeons' "Joint Motion Methods of Measuring and Recording" (1963).
Angular velocity refers to the speed at which a limb's position relative to the adjacent limb changes about an axis of rotation. Angular acceleration refers to the rate at which velocity (speed) changes about an axis of rotation.
In work situations, posture can be measured in several ways. In many cases, postures can be adequately estimated by direct observation. Observations may be estimated with videotapes, which may be played in slow motion or stopped for better viewing. Videotapes also can be used for identification of other stresses and to maintain a permanent record of the job for comparison with the job after interventions are implemented.
Manual goniometers can be used for quantitative measurement of static postures. Electrogoniometer can be calibrated in some cases to track posture for static or dynamic exertions. The accuracy and precision of electrogoniometer must be determined for each application. Their calibration should be checked each time they are used. When used with a computerized data acquisitions system, these systems can be used to track posture over a period of time.
Electromechanical goniometers, placed over a joint's axes of rotation, can be used to obtain the relative orientation (position) of the respective body segments. An electrogoniometer also can be used in conjunction with videotape to document work activities and corresponding postural angles; however, the accuracy and precision of the goniometer system must be certified. These measurements may be differentiated to obtain the angular velocity, or differentiated again to obtain the angular acceleration.
Videotaping or still photography can be used alone if the camera's line of sight is perpendicular to the planes of the measured body segment. In this case, measurements can be made directly form the videotape image. Postural angles may also be measured from a combination of video and live observations, using one to verify the other. The evaluation of awkward postures ordinarily does not require the fine detail that the foregoing techniques/instruments provide.
Measurements of the maximum amount of vibration available to the hand (e.g., "hazard level") are performed using the "basicentric" system. Hand-arm vibration measurements and analyses should be performed according to ANSI S3.34, ACGIH-TLV, and NIOSH 89-106 recommendations. As far as we are concerned, any and all vibration is hazardous.
Ambient temperature should be measured by using a thermometer. A calibrated thermistor or thermocouple can also be used to measure surface temperature readings (e.g., measuring cold exhaust of an air tool venting across the wrist).
Cold temperature magnitude is quantified in degrees Celsius. Exposure pattern is measured as the number of contacts with cold exposure pre minute, and exposure duration is quantified in minutes of exposure.
There is a large body of literature on methods of assessing work organizations and organizational stresses. There are several instruments available.
Now that you know how to determine ergonomic risk factors, read this post to learn the methods recommended for measuring and quantifying these risk factors.
In this post we will discuss the risk factors of Magnitude, Repetition, Duration and Force.
Risk Factor Properties
Magnitude quantifies the extent to which each physical stress is involved.
Measurements of force, posture, recovery, vibration and cold magnitude is reported in terms of the average, peak, or root means square levels for the duration of the specific exertion, motion, or posture.
Repetition measure depends on the level. At the most detailed level, each time a specific exertion is repeated, such as striking a nail with a hammer, one repetition about the elbow occurs. Likewise, striking a key on a keyboard would be considered one repetition. A higher order of quantification for repetition may be the frequency that a cycle for a task repeats. In the case of the hammer, one repetition may be counted every time another nail is hammered. A less detailed study may quantify for many times a hammer is used in the course of a shift. Consequently, different studies quantifying repetition may not be measuring the same thing. This has made it difficult to compare different studies. It is therefore important that repetition measurements specify the specific action and level of detail being measured (micro, element, cycle, task, etc.).
Duration is quantified as the time elapsed when a specific exertion is performed or a posture is assumed. At the most detailed level, duration is the movement time or exertion time for a specific muscle-tendon group or body region (e.g., right hand and wrist). Less detailed analyses use element times, cycle times, or task time as measures of duration.
Forces may be either external or internal forces. An external force can be defined as a force applied, voluntarily or involuntarily, to the surface of the body. In general, internal forces increase joint's torque, angular velocity or acceleration. Since internal forces are not conveniently measured, the term "force" shall refer to external forces unless specifically indicated.
The following methods are available for quantifying force:
- Rough approximations
- Simple mechanical scales
- Electronic load cells
Simple mechanical devices such as a spring scale or dynamometer can be used to estimate lift/pull/push forces in many instances. (Note: Care must be taken to ensure the alignment of the scale or dynamometer with the actual axis of the exertion.) Electronic versions of these devices can be connected to a recording device or computer to provide more accurate force-time data for dynamic tasks.
Direct force measurements are often difficult to obtain. Forces can often be roughly calculated using the weight of the objects, estimates of the frictional forces, the power settings on tools, and simple physics equations.
Internal muscle forces are difficult to measure, but can be estimated with Electromyography (EMG) by trained personnel using specialized equipment. Under controlled conditions, internal muscle forces can be estimated by simulating the motions and exertions in a laboratory setting. If internal forces are measured, sufficient replicate measurements should be made to account for variability within and between individuals performing the task.
Pressure and force can be measured using ink force sensors and strain gauges, but this is rarely done due to difficulties in using the equipment. The conditions that cause high contact stresses are well recognized and are usually eliminated without measuring the level of stress.
Element exertion and recovery periods should be measured for each relevant muscle- tendon group, body region or joint.
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In Part II of this post series, we will discuss: Posture and Motion, Vibration, Cold Temperatures, Work Organization and Psychosocial & Psychophysical factors.
Currently available data have identified that risk factors for Work-Related WrMSDs include exposure to physical stress in manual work. Physical stress arises from physical attributes of the work, workstation, tools, materials and equipment. Properties of physical stress are affected by job design and work organizational factors. The presence or absence of physical stresses and the level of their properties are assessed through job analyses.
Typically job analyses addresses the following physical stresses:
- Posture and motions
Job analysis quantifies the following properties of each physical stress factor:
- Repetition or frequency
Job analysis also considers job and work organization factors that can alter the characteristic properties of physical stress exposure.
A combination of risk factors rather than any single risk factor may be responsible for the occurrence of WrMSDs. Therefore, identifying all the risk factors that may be present in the job is important.
For an identification of the different types of ergonomic risk factors and workplace hazards: