ergonomics of computer usage

Ergonomics Ergonomics of Computer of Computer

UsageUsageDr Sanjoy SanyalDr Sanjoy SanyalMBBS, MS, MSc (UK), ADPHA, ADHRDMBBS, MS, MSc (UK), ADPHA, ADHRD

SeychellesSeychelles

Presented in Seychelles medical college in September 2007

A few simple measures can avoid a lot of pain in the neck (pun unintended!)

Posturing body partsPosturing body parts

1.1. ComputerComputer directly in front directly in front

2.2. ForearmsForearms horizontal horizontal

3.3. WristsWrists in neutral, comfortable in neutral, comfortable positionposition

4.4. Upper armsUpper arms hang naturally at sides hang naturally at sides

5.5. BreaksBreaks during sessions during sessions

Upper limbsUpper limbs

WristsWrists in neutral position, neither in neutral position, neither bent up, down nor sideways. bent up, down nor sideways.

Do not lean wrists on wrist-straps Do not lean wrists on wrist-straps while typing. while typing.

ShouldersShoulders / / armsarms relaxed and relaxed and hanging naturally.hanging naturally.

Elbow / forearmElbow / forearm rest comfortably rest comfortably on work surface, parallel to floor; on work surface, parallel to floor;

ElbowElbow at 90-degree angle. at 90-degree angle.

Lower limbsLower limbs Back of kneesBack of knees extending no more than 3- extending no more than 3-

4 finger lengths from end of chair.4 finger lengths from end of chair. ThighsThighs parallel to floor, comfortably parallel to floor, comfortably

supported on seat of chairsupported on seat of chair Leg-torso angleLeg-torso angle = 90-100 degrees = 90-100 degrees FeetFeet in front of seat and resting flat on in front of seat and resting flat on

floor. floor. If feet are not reaching floor, adjust height If feet are not reaching floor, adjust height

of chair, or put a footrest under feet.of chair, or put a footrest under feet.

Wrong workstation Wrong workstation postureposture

Correct workstation Correct workstation postureposture

Spine and backSpine and back

BackBack in full contact with backrest in full contact with backrest Lumbar curveLumbar curve of chair fitting lumbar of chair fitting lumbar

spine spine Avoid improper Avoid improper bodybody alignmentalignment NeckNeck straight or slightly forward. straight or slightly forward. Avoid looking up and improper neck Avoid looking up and improper neck

postureposture

ChairChair

Adjustable backrestAdjustable backrest - tilts easily, - tilts easily, yet provides solid back supportyet provides solid back support

Curved Curved lumbar supportlumbar support Able to be raised / lowered, swiveled / Able to be raised / lowered, swiveled /

locked at different angleslocked at different angles Average adultAverage adult: Seat 1½ feet (45 cm) : Seat 1½ feet (45 cm)

above ground, placed 1½ feet (45 cm) above ground, placed 1½ feet (45 cm) from table; table 2 -2 ½ feet (60-75 from table; table 2 -2 ½ feet (60-75 cm) high.cm) high.

EyesEyes Avoid locking eyes into Avoid locking eyes into fixed-screen starefixed-screen stare. . ‘‘Rule of 30Rule of 30’: Every 30 minutes look ’: Every 30 minutes look

towards an object approximately 30 feet towards an object approximately 30 feet away, for 30 seconds.away, for 30 seconds.

Keep eyes levelKeep eyes level with upper margin of with upper margin of monitor monitor

Should not be necessary to swivel eyes Should not be necessary to swivel eyes downwards >downwards >40 degrees40 degrees from horizontal from horizontal when looking from top to bottom of screen.when looking from top to bottom of screen.

Workstation setupWorkstation setup

Workstation setupWorkstation setup

Workstation setupWorkstation setup

Desktop screenDesktop screen

Anti-glareAnti-glare screen. screen. In front of a window, its back facing the In front of a window, its back facing the

window. window. Screens Screens << 17 inches 17 inches (43 cm) should be (43 cm) should be

one-arm + 3 inches away from fingertips. one-arm + 3 inches away from fingertips. Larger screensLarger screens 7-8 inches away from 7-8 inches away from

fingertips.fingertips. OrOr, 1 ½ to 2 feet (45 to 60 cm) from eyes., 1 ½ to 2 feet (45 to 60 cm) from eyes. Screen directly in frontScreen directly in front of user’s eyes, not of user’s eyes, not

angled in vertical or horizontal axes.angled in vertical or horizontal axes.

Laptop screenLaptop screen

Adjust viewing angle for: Adjust viewing angle for: Best display Best display Least eye strainLeast eye strainLeast muscle fatigueLeast muscle fatigueOptimum brightnessOptimum brightness

Desktop peripheralsDesktop peripherals Top margin of Top margin of monitormonitor at eye-level. at eye-level. MouseMouse to right or left of keyboard, at same to right or left of keyboard, at same

height.height. KeyboardKeyboard located at elbow height located at elbow height ‘‘B'-keyB'-key lined up with the navel lined up with the navel Keyboard legsKeyboard legs should be knocked down, so should be knocked down, so

that it lies flat on tablethat it lies flat on table Wrist-restsWrist-rests may be used to reduce strain may be used to reduce strain

on wrists.on wrists.

Room lightingRoom lighting

Work areaWork area adequately lit / ventilated. adequately lit / ventilated. Windows/lightsWindows/lights should not create should not create

glare / reflection on displayglare / reflection on display Indirect lightIndirect light to avoid bright spots on to avoid bright spots on

displaydisplay Overhead lighting is best, orOverhead lighting is best, or Fluorescent light with a grid or shield Fluorescent light with a grid or shield

covering the fixturecovering the fixture

“Keep head on your shoulders,Watch your hand, Look straight, Keep an eye on your back.”

References References

Dr Venkata Ramana RaoDr Venkata Ramana Rao, RSI , RSI specialist, myotherapist and specialist, myotherapist and ergonomist; RSI Healthcare.ergonomist; RSI Healthcare.

Rich EpsteinRich Epstein, Director of the Moore , Director of the Moore Center for Rehabilitation, Stamford Center for Rehabilitation, Stamford and a founder of the Moore Center and a founder of the Moore Center Ergonomics and Injury Prevention Ergonomics and Injury Prevention CompanyCompany