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With regard to the monitor, one must take in to consideration how the placement and maintenance of the monitor can effect both the eyes and the musculoskeletal system. The following suggestions can help precent the development of eye strain, neck pain and shoulder fatigue while using your computer workstation:
Make sure the surface of the viewing screen is clean.
Adjust brightness and contrast to optimum comfort.
Position the monitor directly in front of user to avoid excessive twisting of the neck.
Position the monitor approximately 20-26 inches (arm's length) from user.
Tilt top of the monitor back 10 to 20 degrees.
Position monitors at right angles from windows to reduce glare.
Position monitors away from direct lighting which creates excessive glare or use a glare filter over the monitor to reduce glare.
The top of the viewing screen should be at eye level when the user is sitting in an upright position. Note: Bifocal wearers may need to lower monitor a couple of inches.
Adjusting Your Chair
Contrary to popular belief, sitting, which most people believe is relaxing, is hard on the back. Sitting for long periods of time can cause increased pressure on the intervertebral discs, the springy, shock-absorbing part of the spine. Sitting is hard on the feet and lungs. Gravity tends to pool blood in the legs and feet and create a sluggish return to the heart. The following recommendations can help increase comfort for computer users:
- "Dynamic sitting", don't stay in one static position for extended periods of time.
- When performing daily tasks, alternate between sitting and standing.
- Adjust height of backrest to support the natural inward curvature of the lower back.
- It may be useful to use a rolled towel or lumbar pad to support the low back.
- The backrest angle is set so that your hip-torso angle is 90 degrees or greater.
- Adjust height of chair so feet rest flat on floor (use footrest if necessary).
- Sit upright in the chair with the low back against the backrest and the shoulders touching the backrest.
- Thighs should be parallel to the floor and knees at about the same level as the hips.
- Back of knees should not come in direct contact with the edge of the seat pan (there should be 2-3 inches between the edge of the seat and the back of the knee).
- Don't use armrests to slouch.
- Adjust height and/or width of armrests so they allow the user to rest arms at their sides and relax/drop their shoulders while keyboarding.
- Where armrests are used, elbows and lower arms should rest lightly so as not to cause circulatory or nerve problems.
If you are like many computer users, your computer, keyboard, and mouse are resting on your desk or a portable computer workstation. There is no specific height recommended for your desktop; however, the working height of your desk should be approximately elbow height for light duty desk work.
To allow for proper alignment of your arms your keyboard should be approximately 1 inch to 2 inches above your thighs. Most times this requires a desk which is 25 inches to 29 inches in height (depending upon size of individual) or the use of an articulating keyboard tray. The area underneath the desk should always be clean to accommodate the user's legs and allow for stretching.
The desktop should be organized so frequently used objects are close to the user to avoid excessive extended reaching. If a document holder is used, it should be placed at approximately the same height as the monitor and at the same distance from the eyes to prevent frequent eye shifts between the screen and reference materials.
Keyboard and Mouse Placement
Many ergonomic problems associated with computer workstations occur in the forearm, wrist, and hand. Continuous work on the computer exposes soft tissues in these areas to repetition, awkward postures, and forceful exertions.
The following adjustments should be made to your workstation to help prevent the development of an ergonomic problem in the upper extremities:
- Adjust keyboard height so shoulders can relax and allow arms to rest at sides (an articulating keyboard tray is often necessary to accommodate proper height and distance).
- Keyboard should be close to the user to avoid excessive extended reaching.
- Forearms parallel to the floor (approximately 90 degree angle at elbow).
- Mouse should be placed adjacent to keyboard and at the same height as the keyboard (use articulating keyboard tray if necessary).
- Avoid extended and elevated reaching for keyboard and mouse. Wrist should be in neutral position (not excessively flexed or extended).
- Do not rest the hand on the mouse when you are not using it. Rest hands in your lap when not entering data.
Lighting not suited to working with a Video Display Terminal is a major contributing factor in visual discomforts including eyestrain, burning or itching eyes, and blurred or double vision. Typical office environments have illumination levels of 75 to 100 foot-candles, but according to the American National Standards Institute (ANSI), computer workstations require only 18 to 46 foot-candles. Use the following recommendations to reduce eyestrain and eye fatigue:
- Close drapes/blinds to reduce glare. Adjust lighting to avoid glare on screen (light source should come at a 90 degree angle, with low watt lights rather than high.) Place monitor at 90 degree angle to windows (where possible). Reduce overhead lighting (where possible). Use indirect or shielded lighting where possible. Walls should be painted medium or dark color and not have reflective finish.
- Use a glare screen to reduce glare (alternatively, place a large manila folder on top of the monitor and let it hang over the monitor 2 inches to 3 inches to reduce glare from overhead lighting).
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Whole-body vibration is experienced in any work condition that involves sitting, standing, or lying on a vibrating surface. Excessive levels and durations of exposure to whole-body vibrations may contribute to back pain and performance problems. If you spend a considerable amount of your work day on a vibrating seat or floor and experience any of the following signs or symptoms contact your Safety and Health Specialist
- Blurred vision.
- Decrease in manual coordination.
- Drowsiness (even with proper rest).
- Lower back pain.
- Upset stomach.
Vibrating hand tools or work pieces transmit vibrations to the holder, and depending on the vibration level and duration factors, may contribute to Raynaud's syndrome or vibration-induced white finger disorders. These disorders show a progression of symptoms beginning with occasional or intermittent numbness or blanching of the tips of a few finger to more persistent attacks, affecting greater parts of most fingers and reducing tactile discrimination and manual dexterity. If you notice the onset of any of these symptoms, contact your Safety and Health Specialist
The following recommendations can help reduce the likelihood of developing hand-arm vibration syndromes:
- Select power tools with anti-vibration properties.
- Use handle coatings that suppress vibrations. Increase coefficient of friction on handles to reduce force requirements.
- Keep power tools balanced and lubricated to minimize vibration.
- Incorporate job rotation. Have more than one person perform tasks that involve exposure to hand-arm vibration.
- Use vibration attenuation gloves.
Hand Tool Use and Selection Principles
Implementing the following suggestions for proper selection and usage of hand tools will help reduce the likelihood of developing work-related musculoskeletal disorders (WMSDs) in the hands, wrists, and arms:
- Maintain straight wrists. Avoid bending or rotating the wrists; a variety of bent-handle tools are commercially available.
- Avoid static muscle loading. Reduce both the weight and size of the tool. Do not raise or extend elbows when working with heavy tools. Provide counter balance support devices for larger, heavier tools.
- Avoid stress on soft tissues. Stress concentrations result from poorly designed tools that exert pressure on the palms or fingers. Examples include short-handled pliers and tools with finger grooves that do not fit the worker's hand.
- Reduce grip force requirements. The greater the effort to maintain control of a hand tool, the higher the potential for injury. A compressible gripping surface rather than hard plastic should be used.
- Whenever possible, select tools that use a full-hand power grip rather than a precision finger grip.
- Avoid sharp edges and pinch points. Select tools that will not cut or pinch the hands even when gloves are not worn.
- Avoid repetitive trigger-finger actions. Select tools with large switches that can be operated with all four fingers.
- Wear gloves that fit. Tight-fitting gloves can put pressure on the hands, while loose-fitting gloves reduce grip strength and pose other safety hazards.
If your job involves the frequent use of hand-tools and you frequently experience numbing, blanching, pins-and-needles, or dull pain in the hands or forearms, contact your Safety and Health Specialist.
The following are recommended for control of ergonomic hazards associated with repetitive pipetting:
Use pipettes with newer trigger mechanisms requiring less force to activate, and use the pointer finger to aspirate and the thumb to dispense (e.g., Rainin-Latch Mode Pipette). For more information see Laboratory Ergonomic Equipment
Use pipettes that fit comfortably in the user's hand.
For tasks such as mixing or aliquotting, use an electronic pipette with mixing functions.
Use a multichannel pipette for large aliquotting tasks.
Take micro-breaks of 2 minutes for every 20 minutes of pipetting. Mild hand exercises and stretches are beneficial (see Exercises
Clean pipettes on scheduled basis (this reduces "sticking" and improves quality of work).
Adjust the workstation so the individual doesn't have to work with their arms in an elevated position. Work with arms close to the body.
Rotate pipetting activities between laboratory tasks, hands, and people.
Use thin-wall pipette tips that fit correctly and are easy to eject.
Use minimal force when applying pipette tips.
Keep samples and instruments within easy reach.
If it is necessary to stand for long periods of time during pipetting, use an anti-fatigue matting.
The following are recommended to control hazards associated with microscopy:
- Try pulling the microscope toward the edge of the work surface to position the operator in a more upright posture.
- Try elevating the microscope. This can help position the operator in a more upright posture and reduce rounding of the shoulders and neck.
- Maintain neutral spine.
- Use an ergonomically designed chair that provides adequate back support, adjustable height, and adjustable seat angle.
- Use armrests to support the operator's forearms while using adjustment knobs on the microscope.
Proper Workstation Setup for Microscopy
Biosafety Cabinets and Laboratory Workbenches
The following are recommended for control of ergonomic hazards associated with biosafety cabinets and laboratory workbenches:
- Use an ergonomically designed chair that provides adequate back support, adjustable seat angle, and height adjustability between 28 inches to 33 inches.
- Use footrests for individuals whose feet do not rest comfortably on the floor.
- Apply closed-cell foam padding to the front edge of the biosafety cabinet (away from the downdraft) or workbench. This reduces contact forces by increasing the surface area that comes into contact with the forearm and therefore reduces the chances of impinging nerves, tendons, or blood vessels. If applying closed-cell padding to front edge of biosafety cabinet, make sure the material can be properly decontaminated.
- Remove drawers, supplies, refrigerators, etc. from under the workbenches and cabinet doors from under biosafety cabinets (provides leg room).
- Use a turntable to store equipment near the worker. This reduces excessive reaching and twisting, which places an increased load on the low back.
- Use anti-fatigue matting for laboratory personnel who must stand for extended periods of time.
- Take frequent micro-breaks to perform stretching exercises (see ).
New biosafety cabinets may be purchased that incorporate the features below. Desirable features for the new biosafety cabinets include:
- A perforated front grill reduced by 1 inch to 2 inches to bring the work platform closer to the laboratory worker-adjustable height (hand-crank or hydraulic lift). Non-glare glass on the sash window and/or adjustable Plexiglas barriers.
- A platform configuration with "wells" for placement of tall containers.
Microtome or Cryostat
The following are recommended for control of ergonomic hazards associated with microtome or cryostat use:
- Lower the workstation to keep arms closer to body.
- Apply padding to the front edge of work surface to eliminate sharp edges and increase the amount of blood flow to the hands.
- Retrofit the existing handle with an adapter that will allow the operator to use the hand-wheel in a pistol grip position. This will alleviate repetitive wrist flexion and extension.
- Consider use of an automatic foot operated cryostat when frequent cryo-sectioning is performed.
- Avoid placing utensils such as forceps inside the cryostat.
- Use an ergonomically designed chair (see What features make up an ergonomically designed chair?).
- Take frequent "micro-breaks". These breaks should be used to perform stretching exercises, especially the hands (see Exercises).
The use of a flow cytometer requires frequent lateral bending, neck and back flexion, and extended arm reaching. This is due to the receiving port being located on the bottom of the flow cytometer. The operator must sit in awkward positions in order to see the controls. The following are recommended for control of ergonomic hazards associated with using a flow cytometer:
- Raise the flow cytometer by placing a block between the flow cytometer and the workbench.
- Use an electric or hydraulic adjustable table. Each individual will be able to adjust the flow cytometer to a height which is most comfortable.
- Use an ergonomically designed chair (see What features make up an ergonomically designed chair?).
- Place the top of the monitor so the top of the screen is approximately at eye level.
Glove Boxes or Anaerobic Chambers
Working in glove boxes or anaerobic chambers requires extended static loading on the shoulders. Extending the arms for more than a couple of minutes can become very exhausting. In addition to static loading and frequent side reaching, the thick gloves also make the user over compensate on grip strength. The following are recommended for control of ergonomic hazards associated with using a glove box:
Manipulating Centrifuge Rotors
Centrifuge rotors present a unique lifting hazard in the laboratory. The following are recommended for control of ergonomic hazards associated with lifting centrifuge rotors:
- Use a second person to assist with the lift.
- Use a cart to transport rotors.
- Look for manufacturers' which produces lighter weight rotors.
- Implement a pulley system, which would attach to the ceiling directly above the centrifuge.
Micro-Manipulation and Fine Motor Skills
The following are recommended for control or ergonomic hazards associated with micro-manipulation techniques:
Use plastic vials with fewer threads. This will reduce twisting motions during capping and uncapping lids.
Use small pieces of foam similar to the type used on pencils and pens, to prevent soreness on the fingertips, where fingers and forceps articulate. This will distribute the force over a greater surface area, thus reducing the compressive forces on the soft tissue.
Practice using the forceps between the 1st and 2nd digits instead of using the thumb and 1st digit. Then try alternating between the two positions to reduce the use of the
thumb. The thumb is used repetitively with almost every job task performed in the laboratory (see sketch at right).
Tilt storage bins toward the worker to reduce wrist flexion while reaching for supplies.
Encourage micro-breaks and hand exercises (see Exercises
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Assisting another individual in a change of position requires proper body mechanics on your part. Proper body mechanics (positioning) will make your job easier to perform and reduce the risk of injury. Proper body mechanics requires that the natural curves of the spine are maintained in proper alignment. Look at the natural curves of your back and understand how to successfully maintain these curves:
- Bend your knees to get up and down.
- Keep the object close to the body in order to minimize forces on your body.
- Pivot and don't twist.
- Don't try to do more than you can handle. Respect your limits.
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