Ergonomics Working Group


Question: How much weight should a child carry in their backpack?

Answer: While a backpack is still one of the best ways to bear carry items, a too-heavy or improperly worn backpack may harm joints and muscles. Estimates on back pack weight (bag and contents) range from 15 to 20 percent of the child's body weight. Some simple rules of thumb to aid in backpack use are use both shoulders when using the backpack this will distribute the weight more evenly. Pull backpack straps tight so the load rests close against the back. Purchase backpacks with a chest and waist straps, these straps will distribute some of the weight from the back to the chest and hips. Finally place heavier items up high. The higher the center of gravity of the backpacks contents the lower amount of stress is placed on the back.

Question: Do wrist rests work?

Answer: Like all other products knowing how something works influences the usefulness of the product. A wrist rest is intended to act as a cushioned support for the wrists while typing. This support will reduce the amount of contact stress the wrist is exposed to. Guidelines to select the proper wrist rest for your workstation are the back edge of the wrist rest should match the height, width, and shape of the front edge of the keyboard. The wrist wrest padding should be cushioned but not too soft. A mistake many people make when using a wrist rest is parking their wrists on the support and extending their fingers to reach the keyboard key.Ideally when typing the hands and fingers should move fluidly with the wrists sliding up and down and side-to-side on the wrist rest.

Question: Does release surgery solve carpal tunnel syndrome?

Answer: No. Surgery does not address the problems of carpal tunnel syndrome (CTS), it only addresses the symptoms that are causing pain. Carpal tunnel syndrome is an irritation of the median nerve due to the tendons in the wrists becoming inflamed and putting constant pressure on the nerve. This irritation is what eventually will lead to the classic symptoms of CTS (tingling, pins and needles sensation, numbness, hand clumsiness). Release surgery if successful will eliminate these symptoms by freeing up more space in the carpal tunnel (a ligament in the wrist is split). This extra room eliminates the tendons constantly irritating the median nerve. Keep in mind that on average the hand only has about 70 percent of its normal strength after a patient recovers from surgery. Also if no work or lifestyle changes are made after surgery the risk factors that contributed to CTS from developing still exist and will lead to a relapse.

Question: I am a safety manager and I notice that people still sit in chairs with only four-legs, is this ergonomically correct?

Answer: The number of legs on a chair is not an ergonomics issue but a safety issue. According to Department of Defense Design Criteria Standard Human Engineering aka Military Standard 1472-F paragraph Seat base. Chairs shall have at least four supporting legs. Swivel chairs should have five supporting legs. The greater the number of legs the more durable the chair and the less likely it will tip if body weight is shifted. Virtually all swivel chairs manufactured today meet the five-legged criteria and therefore should be provided to all employees who need one.

Question: How do I determine if a chair I plan on buying is ergonomically designed?

Answer: The use of the term ergonomic is not regulated by government therefore any chair manufacture can label a chair ergonomically designed. In order for a chair to be ergonomically designed it needs to be adjustable, provide support, and be contoured correctly. We developed USACHPPM Fact sheet 88-004-0599 which contains an extensive checklist based on multiple ergonomic standards and good ergonomic principals. If the chair you are planning on buying meets all criteria listed on the fact sheet then you can feel confident you are buying an ergonomically designed chair.

Question: My job description lists that I need to be able to lift 70 pounds. Is this excessive?

Answer: Yes or No, it depends on who you listen to. According to Department of Defense Design Criteria Standard Human Engineering aka Military Standard 1472-F table XVII. Maximum design weight limits. A man can lift 87 pounds and a woman 44 pounds. The National Institute for Occupational Safety and Health claims that 99 percent of male and 75 percent of females in the work population can lift a maximum of 51 pounds. Another standard commonly used was developed by the Liberty Mutual Insurance Company, they recommend that the strongest men and women can lift 167 pounds and 83 pounds respectively. Keep in mind all these weights are under ideal conditions. As your working environment and task requirements deviate from ideal the amount of weight you can safely handle is significantly lower. This is the danger in just assigning a number to a job description; as any ergonomist can tell you it is not the weight being lifted that matters. It is the posture of the body when the lift is being made, the number of repetitions the lifter has to make and the duration of the lifting task that influences how much weight we can safely lift. The majority of all back injuries due to lifting occur in the 35 to 50 pound range. Ideally from an ergonomics perspective the less weight you lift the better, so always try to use a mechanical device or help from a co-worker when performing a lift.

Question: I was told that it is easier to lift 20 pounds of bricks than 20 pounds of feathers. I thought 20 pounds was 20 pounds.

Answer: You are right 20 pounds is 20 pounds they both weigh the same. However weight alone does not influence how easy it is to lift something or the stress it puts on your back. Stress on the back is dictated by both the weight being lifted and the distance the weights center of gravity is from the back. Since the feathers are bulkier than the bricks their center of gravity is further away from the back. This is why 20 pounds of bricks is easier to lift than 20 pounds of feathers.

Question: My wrists hurt when I type, will an alternately designed keyboard help?

Answer: It could, the deciding factor is what is causing the wrists to be in pain when you type. An alternatively designed keyboard will improve your wrist posture. If this is the primary risk factor causing you pain then the keyboard will reduce or eliminating the pain you are experiencing. However there are other risk factors associated with typing they are repetition (strokes per minute) duration (how long do you type during the day), work rest scheduling (do you take small frequent breaks 1-5 minutes during the day), force used to strike the keys, and contact stress (are the wrists resting on a hard or sharp surface when typing or are you wearing tight fitting jewelry such as a watch or bracelet on the wrist. A new keyboard may help but it is important to examine the other risk factors you are exposed to.

Question: Are there any easy tips I can use to set up my computer workstation?

Answer: Setting up a computer workstation that is comfortable to work at is easy to accomplish. Here are some helpful hints. The more adjustable the workstation the better, get a chair that is height adjustable, has an adjustable lumbar support, and has adjustable armrests. Get a desk that is adjustable. If this is not possible you can raise the desk height by placing blocks under the desk. The monitor should be placed in front of you so your neck does not twist, also the top of the monitor (not the top of the screen) should be positioned at eye level. The keyboard should be placed directly in front of the monitor and your bellybutton should be positioned in front of the "b" key on your keyboard. When typing your elbows should be bent 90 degrees and be close to your sides whenever you type or mouse, plus the arms, wrist, and hands should be in line with no twisting or bending. Lastly your knees should be positioned about an inch higher than your hips and your feet should resting firmly on the ground. If you are a shorter person the use of a footrest may be needed. For more in depth information please refer to the DOD Ergonomics Working Group publication Creating the Ideal Computer Workstation: A Step-by-Step Guide, it can be found on the internet at

Question: Why does my shoulder hurt when I use my mouse?

Answer: Many workstations were designed and purchased before the advent of mouse driven software. Think back 10 years ago, if you wanted to use your file manage you hit shift and the F7 keys or spell check was Ctrl and F2. Now to do virtually any command you use a mouse. Workstations that are designed for mouse driven software have an adjustable tray that moves up and down and is large enough to accommodate a keyboard, wrist rest and mouse. My guess is your workstation does not have a keyboard tray that can fit all the above-mentioned items. Since not using a mouse is not an option your mouse rests on top of your desk, whenever you use your mouse you must fully extend your arm. This full arm extension causes stress to the shoulder since the shoulder muscle now must support the entire weight of your arm. As a rule of thumb the elbows should be bent 90 degrees and be close to your sides whenever you type or mouse.

Question: Are LCD Monitors "Easy on the Eyes?"

Answer: Computer users have traditionally used a CRT (Cathode Ray Tube) monitor. New technology has made the flat-screen LCD (Liquid Crystal Display) monitors very popular because they are compact, lightweight, and take up far less desktop space. As part of the life cycle replacement of computer systems, some people are purchasing LCD monitors because of their flat configuration. Are these ergonomically sound purchases?

  • The Pros and Cons
  • A top-of-the-line LCD screen is easier on your eyes than a top-of-the-line CRT monitor.
  • Flat screens are more effective in reducing glare, thus providing more comfort to your eyes.
  • As far as screen size is concerned, it is true that LCD screens are generally smaller than CRTs, but they do come in 17-inch diagonals large enough for virtually all users. Also, flat screens have a much smaller depth. This allows you to more comfortably position the screen on your desk.
  • The CRT screen has a trace amount of electromagnetic radiation and the LCD has zero emissions. Neither - CRT or LCD screens pose an electromagnetic radiation health hazard both are completely safe.The bottom line is you get what you pay for: When replacement of your old CRT monitor is required, a "high-end" LCD screen is a smart choice. It provides both good resolution and is easily positioned/adjusted on your desk.

Question: Will I still need a keyboard tray if I use a flat screen monitor?

Answer: There is no research currently available regarding flat screen monitors and workstation set-up.Having a flat screen monitor will increase your usable desk space, but having this extra space available does not guarantee you will be able to use your keyboard comfortably. Most likely, your seat pan height will need to be raised if the keyboard is on your desk and you may need to acquire a foot rest. If you keeps files, documents, etc., on your desk then having a keyboard on your desk might be a source of frustration. Ultimately, a case by case assessment needs to be made to determine if a keyboard tray is needed when a flat screen monitor is provided at the workstation.

Question: What safety guidelines should I follow when using my laptop computer?

Answer: The ideal "ergonomic" computer workstation includes an adjustable desk and chair with a separate computer screen, keyboard, and mouse. Adjustable furniture and separate computer components can be made to "fit" your needs, rather than you trying to adjust to the limitations of the workstation.

But the design of laptop computers defies these basic ergonomic guidelines. Laptop users set up shop on any available surface, often in cramped spaces - a classroom desk, a conference table, an airplane tray, a hotel bed, their own laps. Chairs are anything available to sit on from a folding chair to a lobby couch to a park bench. The computer screen, keyboard, and mouse are all-in-one units that create a single, fixed design with typically smaller features than in a standard computer set-up.

Question: What is the impact of overtime on productivity?

Answer: Overtime is often used as a solution for personnel shortages or to meet peak production demands and schedules. Although management may view overtime as a temporary solution, it often becomes a standard way of managing work demands. In many instances, the extended overtime hours approach the same hours worked in a 12-hour shift system; however, the use of overtime is applied with little consideration to the consequences of this work pattern or the scheduling of rest days. The worker fatigue resulting from extended work hours is very costly in terms of worker health, performance, and morale.

The health effects of extended work hours are well documented and include an increased risk for:

  • Cardiovascular disease
  • Sleep disorders
  • Depression
  • Ulcers
  • Gastrointestinal dysfunction and disorders
  • Breast cancer
  • Complications of existing medical conditions such as diabetes and epilepsy

These health effects become even more apparent in older workers. In addition, extended hours reduce the available time to spend quality time with family members and meet family care demands, leading to increased levels of stress, irritability, and feelings of isolation. The risk of substance abuse also increases as workers resort to caffeine, stimulants, and tobacco to stay awake and alcohol and depressant drugs to fall asleep. Workers who consistently work under an extended hours schedule report high levels of concern that these extended hours are affecting their health and longevity. Typically, excessive use of overtime is accompanied by a characteristic increase in absences for sickness and accidents.

The productivity and performance costs are often not apparent to management, but these costs can far exceed the direct costs of overtime. The worker fatigue resulting from extended hours leads to increased errors and accidents, decreased concentration, slower reaction time, failure to perceive and react to critical signals, impaired motor skills and coordination, decreased ability to handle stress, reduced problem-solving and decision-making abilities, and increased risk-taking behavior.

Dramatic examples of fatigue-related accidents include the chemical spill in Bhopal, India; the nuclear accidents at Three-Mile Island and Chernobyl; and the Exxon Valdez oil spill. Driving is a serious concern. A recent study found that fatigued drivers perform worse than those with a blood alcohol level of .05 percent. Finally, productivity levels and work output do not increase in proportion to the hours worked. In fact, extending the workday often causes the tempo of work to slow down and the hourly output to decrease, especially in physically demanding jobs.

Question: Are laboratory researchers at risk for repetitive motion injuries?

Answer: Most certainly! Laboratory researchers are at risk for repetitive motion injuries during routine laboratory procedures such as pipetting, working at microscopes, operating microtomes, using cell counters and even using video display terminals. Depending on how these tasks are performed researchers are exposed to multiple repetitive motion injury risk factors such as poor postures, dynamic and or static work (often times both are occurring but to different body parts, contact stress, forceful exertions, and long task durations.

Question: Can pipetting for a couple of hours at a time cause me discomfort?

Answer: Pipetting is one of the most common tasks performed in the research laboratory. It involves several ergonomic stressors - thumb force, repetitive motions, and awkward postures, especially of the wrists, arms, and shoulders. There are engineering and administrative controls that can be implemented which may eliminate or lessen risk factors which in turn can reduce the discomfort associated with pipetting.

Engineering Controls:

  • Use pipettes with newer trigger mechanisms requiring less force to activate, and use the pointer finger to aspirate, and the thumb to dispense
  • Use pipettes that fit comfortably in your hand.
  • For tasks such as mixing or aliquotting, use an electronic pipetter with mixing functions.
  • Use a multichannel pipettor for large aliquotting tasks. Use shorter pipettes.
  • This decreases hand elevation and consequent awkward postures.

Administrative Controls:

  • Take micro-breaks of 3-5 minutes for every 20-30 minutes of pipetting. Mild hand exercises and stretches are beneficial.
  • Clean pipetters on a regularly scheduled basis - this reduces "sticking" and improves quality of work.
  • 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.

Question: My computer laboratory is not set-up as nicely as my office computer workstation. Do you have any recommendations?

Answer: The reality is many researchers spend 50% or more of their day entering data with their keyboard and mouse resting on a lab bench and within infectious disease laboratories, the establishment of primary computer workstations for office work is not recommended. This results in using lab benches that are too high and require the researcher to elevate the arms and excessively deviate the wrists while inputting data. The following engineering controls are recommended for control of ergonomic hazards associated with the use of computers in the lab:

  • Install adjustable keyboard platforms under lab benches which accommodate use of the mouse beside the keyboard.
  • Provide fully adjustable seating.
  • Place monitors so the user's viewing distance is between 18 and 30".
  • Place monitor so the top of the screen is approximately eye level. This allows the eyes to naturally gravitate toward the center of the screen.
  • Use a document holder placed adjacent to and in the same plane as the computer screen.
  • Provide foot rests, where possible, for individuals in order for them to change leg positions throughout the day.
  • Provide for a choice of keyboards and mouse or other input devices for individuals who have existing musculoskeletal problems.
  • Where possible, position computer workstations in corners or other areas away from doors, entrances, and passageways.

The following administrative controls are recommended for control of ergonomic hazards associated with the use of computers in the lab:

  • Encourage mini-breaks of 3 to 5 minutes for every 20 - 30 minutes of keyboarding or mouse work. These breaks can be spent doing mild hand exercises or stretches.
  • Laboratory personnel should not go from keyboarding to pipetting activities (or vice versa) without an adequate break (at least 15 minutes) to allow the hands to recover.

Question: My neck bothers me after a full day of using a microscope. Can you recommend anything to make me feel better?

Answer: The first step to feeling better is determining whether the microscope workstation was designed taking into account the dimensions of its potential users. Since laboratory personnel come in many different shapes and sizes, the workstation should be made as adjustable as possible. Ideally, the microscopist should be able to adjust the height of his or her chair, work surface, and microscope. The following are engineering controls are recommended for control of ergonomic hazards associated with the use of microscopes:

  • Try pulling the microscope toward the edge of the work surface to position the operator in a more upright posture.
  • Use a cut-out work table. This puts you close to the scope and gives an area for supporting forearms.
  • If possible, try elevating the microscope or placing it at an angle so you can look directly into the eyepiece. This can help position the operator in a more upright posture and reduce rounding of the shoulders and neck.
  • Provide arm rests to support the operator's forearms while using adjustment knobs.
  • Use an ergonomically designed chair that provides adequate back support, adjustable height, and adjustable seatangle.
  • Make sure there is adequate room under the work surface so the operator can pull the chair up to the ocular(s).
  • Provide footrests and discourage the use of foot rings on stools.
  • Provide sit-stand seats for areas where there is restricted leg room.
  • Use television systems where possible to eliminate the use of binocular eyepieces.

The following are engineering controls are recommended for control of ergonomic hazards associated with the use of microscopes:

  • Do not use a microscope for more than 5 hours per day. Spread the use out over the entire work day. Also, avoid long uninterrupted periods of microscope work.
  • Encourage frequent breaks from microscopy work as well as stretching exercises.

Question: Are there any ergonomic challenges when working in a fumehood?

Answer: Working in a fumehood (aka Biological Safety Cabinet (BSC)) requires laboratory personnel to assume a variety of awkward postures due to limited work access, which restrict arm movement, and therefore significantly increase the amount of stress on joints of the upper limbs, neck, and back. Associated risk factors include:

  • Repetitive motions of the hands, wrist, and forearms, especially when pipetting Constrained knee and leg space, especially in fume hoods and older BSCs
  • Contact pressure on the forearms, wrists and knees, or legs
  • Awkward and static posture of the neck, torso, legs, arms and wrists
  • Constrained body position
  • Overreaching
  • Prolonged standing in unnatural positions or in restricted postures

Preventive measures you can implement immediately or when new equipment is being purchased are:

  • Place materials as close as possible, avoid extended reaching
  • Always assume a proper posture, use adjustable chairs/stools with foot and arm rests.
  • Avoid contact pressure (forearm and wrists contact with sharp edges). Apply appropriate padding to the front sharp edge of the fumehood/BSC to reduce pressure concentration.
  • If performing work in a fumehood or BSC while standing for prolonged periods of time, use an anti-fatigue mat and footrest to reduce muscle, joint, and spinal fatigue.
  • Take short breaks to alter repetitive forearm and wrist motion, relieve joint pressure and contact pressure caused by sharp edges.
  • Reduce eye strain and awkward posture by keeping viewing window of hood/BSC clean, and line of sight unobstructed.
  • Make sure hood/BSC lighting is working properly, good and proper lighting help reduces eye strain.
  • Raise cabinet couple inches upwards to create a more comfortable leg and thigh clearance.

Also new biosafety cabinets that have desirable features may be purchased. 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) may not be possible for all biological safety cabinets or in all labs.
  • Non-glare glass on the sash window and/or adjustable plexiglass barriers.
  • A platform configuration with for placement of tall containers.

Question: Can you provide me with recommendations when using a microtome or a cryostat?

Answer: The following are recommended for control of ergonomic hazards associated with the use of a microtome or cryostat:

  • 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 handwheel in a pistol grip position. This will alleviate repetitive wrist flexion and extension.
  • Consider the use of an automatic foot operated cryostat when frequent cryosectioning is performed.
  • Avoid placing utensils such as forceps inside the cryostat.
  • Use an ergonomically designed chair.
  • Take frequent mini-breaks. These breaks should be used to perform stretching exercises, especially the hands.