Corporate Safety Manual. Chapter 8 Office Ergonomics

Transcription

1 Corporate Safety Manual Chapter 8 Office Ergonomics Last updated: April 2015

2 Office Ergonomics Chapter 8: Office Ergonomics Index Page Introduction to Ergonomics Work-related Musculoskeletal Disorders (WMSD) Ergonomic Hazards Workstation Design Work Surface Ergonomic Chair Adjusting an Ergonomic Chair Movement is Important How to minimize Strain Using a Computer Mouse can Become a Problem Placement for a Computer Mouse A Shorter Keyboard Can Help Advantages of a Shorter Keyboard Disadvantages of s Shorter Keyboard Workstation Job Design Neutral Posture or a Balanced Position Workstation and Work Flow Design General Guidelines for Work Reaches Workstation Design for Foot Tasks Stretches for the Hands and Forearms Stretches for the Neck and Shoulders Stretches for the Back and Legs Workplace Health and Safety Branch 8-1

3 City of Regina Safety Manual 8-2 Workplace Health and Safety Branch

4 Introduction to Ergonomics Office Ergonomics The word ERGONOMICS is made up of two Greek words: ERGOS (WORK) and NOMOS (NATURAL LAWS). In simple words, we can define ergonomics as the science of matching the work (job) to the worker. Office Ergonomics includes workstation design, job design and work environment. A workstation that does not match the workers shape, size and capabilities may hinder task performance. A poorly designed workstation may pose undue physical stress on the worker due to awkward posture, application of force, repetitive movements, or a combination of these factors. Prolonged work in such conditions can result in injuries of the wrist, back, neck, shoulder and elbows in particular; joints and nerves in general. The consequences of poor ergonomic conditions include poor work quality and productivity, and increased Worker s Compensation costs due to lost time and disability. Work-related Musculoskeletal Disorders (WMSD) Work-related musculoskeletal disorders are injuries that involve muscles, and tissues connecting bones, namely tendons and ligaments. Two types of WMSD affect office workers. 1. Prolonged stationary positions resulting in a. Neck ache b. Back ache 2. Combination of awkward posture, repetitive motion, and application of force in an awkward posture resulting in; a. Pain in the wrist and hands b. Shoulder pain WMSD are also called Overuse Syndrome, Over-Exertion Injury, Repetitive Strain Injuries (RSI) Musculoskeletal Injuries (MSI), and Repetitive Motion Injuries (RMI). These different names are used to emphasize the fact that these injuries result when a given part of the body is subject to prolonged strain while performing a task. Depending on the nature of the job, the most frequently affected parts of the office workers body are the torso, including the lower back, shoulders, neck, arms and wrists. For reasons not fully understood, carpel tunnel syndrome (CTS) has become synonymous with all WMSD suffered by office workers operating computers. In reality, carpal tunnel syndrome is considered a relatively rare medical condition. Office Ergonomics, 5 th Edition Canadian Center for Occupational Health and Safety. Hamilton, Ontario Workplace Health and Safety Branch 8-3

5 City of Regina Safety Manual Ergonomic Hazards Hazard Type Causes Prevention Eye Strain/Head Aches Poor Lighting Adequate lighting Glare/Flicker on Proper workstation screen design Awkward posture Equipment maintenance Work-related musculoskeletal disorders (WMSD) Repetitive tasks Poor posture/incorrect seating Incorrect position of monitor, or work equipment Proper work station Adequate job design Comfortable work environment Back ache/strain Improper manual material handling techniques Awkward posture Training in proper lifting technique Proper chairs and work stations Scheduled breaks Work Station Design Work Surface The work surface is the desk, table or bench that an individual works at. If the work surface is too high or too low for the body and the task being done, then the individual is required to perform the tasks in an awkward body position. The chair and/or work surface height should be adjusted properly to suit the individual and the type of work. For typing and keyboarding, the work surface should be about the height of the elbows with the arm hanging straight by the sides. For writing and reading the work surface should be approximately 5cm above elbow height. If the work surface is not adjustable, then the seat height should be adjusted so that the elbows are about the same height as the top of the work surface. The thighs should be horizontal to the floor. If the feet are not resting flat on the floor, use a footrest. 8-4 Workplace Health and Safety Branch

6 Ergonomic Chair Office Ergonomics The chair should enable an individual to work without using awkward body positions or forceful movements. A good chair has the following qualities; Provides back support Can be adjustable Can get close to the work surface Moves easily To encourage good body positions, the height of the seat and the slope and height of the back rest should be adjustable. Adjusting an Ergonomic Chair The following diagrams are provided as an ergonomic guide. Refer to the manufacturer s instructions that came with the chair on how to make the adjustments. If there are problems achieving an adequate adjustment for sitting comfort, consult with a representative from Workplace Health and Safety Branch. Stand in front of the chair. Adjust the height so the highest point of the seat, when in the horizontal position, is just below the knee cap. Sit on the chair and keep your feet flat on the floor. Check that the clearance between the front edge of the seat and the lower part of the legs (at calves) fits a clenched fist (about 2 inches). Workplace Health and Safety Branch 8-5

7 City of Regina Safety Manual Adjust the back rest forwards and backwards as well as up and down so that it fits the hollow in your lower back. If the chair has a lumbar support you can enhance the back support by adjusting it to fill any voids in the back rest s support. Sit upright with your arms hanging loosely by your sides. Bend your elbows at about a right angle (90 degrees) and adjust the armrest(s) height until they barely touch the undersides of the elbows. Tilt the backrest forwards or backwards to gain support for your back. The angle of adjustment should be between degrees. The chair and its adjustment remain constant for the majority of setups in a typical office environment. Movement is Important No matter how well the chair or workstation is designed, problems may arise if attention is not paid to the way the work is done. Working at a computer often involves very few changes in body position. This lack of movement can lead to muscle pain and strain. 8-6 Workplace Health and Safety Branch

8 How to Minimize Strain Office Ergonomics It is recommended that a person take periodic breaks while working at a computer station. Two breaks in addition to coffee or lunch should take place when continuous work is being done at a workstation. Every 20 minutes the person should stand, and take a short walk or stand and stretch. This break should be about a 1 minute. After working at the computer continuously for an hour the person should take a walk or stretch for 5 minutes. Recommendation to avoid strain; Vary the work tasks. Break up keyboarding tasks work by doing other job duties or tasks that involve moving around or changing body position. Try to stand up and move around. Look away from the screen occasionally and focus your eyes on an object far away. Take regular rest breaks to ease muscle aches, eye strain and stress. Relax muscles by stretching and changing position. Hold the stretch for a reasonable time (e.g., seconds). Breathe normally. Do not bounce, pull/push excessively, or lock your joints. You should feel a stretch, but not pain. If you feel pain or severe discomfort, stop stretching. Ask your medical professional for advice. Using a Computer Mouse can become a Problem The mouse is a standard piece of computer equipment. Because most people using a mouse in a workplace setting must use the computer keyboard at the same time, using a mouse regularly involves using the same small muscles over and over again, and can lead to discomfort, pain, and even Workplace Musculoskeletal Disorders (WMSDs). It is important that all elements of the workstation; keyboard, mouse, monitor, the desk itself and work practices; posture, pace, work breaks are addressed. There are two reasons why using a mouse regularly can be hazardous. First, using a mouse requires a person to make small, exact movements with their hand, fingers, and thumb. By positioning, travelling, scrolling, and clicking the mouse again and again, the same small muscles can become tired and overworked. Referring to Figure 1 a workstation of this design can cause: Pain (ache, soreness) on the top of the hand Pain (ache, soreness) around the wrist Pain (ache, soreness) along the forearm and elbow Workplace Health and Safety Branch 8-7

9 City of Regina Safety Manual Formulation of painful nodules, and in the later stages, ganglion cysts, around the joints and along the tendons Numbness and tingling in the thumb and index finger Figure 1 The second reason using a computer mouse can be hazardous is that the placement of the mouse can make it awkward to reach. Computer workstations are designed to have the keyboard directly in front of the person using the computer this results in the mouse being placed in the upper right or left hand corner of the keyboard tray, extending the reach of the user to the mouse (Figure 2). Figure Workplace Health and Safety Branch

10 Office Ergonomics When the mouse is in this position (Figure 2), it is out of 'easy reach' for comfortable hand movements. In order to use the mouse, the person has to reach their arm outwards and forwards (Figure 3) and hold it there unsupported for as long as they are using the mouse. Figure 3 Moving like this, and holding your arm like this, again and again throughout the workday can cause soreness and fatigue by putting an extra load on the muscles in the upper back (Trapezius muscle) and shoulder (Deltoid muscle). Repeated use of the mouse, therefore, can cause aches and pains in the shoulder and neck area. Lower back pain, while not directly caused by the mouse, can also be a problem if the computer user has poor posture and leans forward when they sit. Placement for a Computer Mouse There is no right or wrong place for a mouse. Rather, you must properly assess your work space to ensure you can use the keyboard and mouse without causing discomfort to the body. Some computer workstations (Figure 2) do not utilize the space available to properly position the mouse. An effort must be made to arrange/design the work space to gain better ergonomic function of the arm, wrist and hand when using the mouse. Options to gain the space for better ergonomics may include; For example in Figure 2 a recommendation would be to use a shorter keyboard, one without a number pad. For example in Figure 3 stop working off of the desk top and have an adjustable keyboard tray installed. E.g. Cobra sit/stand keyboard tray. Where there is no room for the previous options, use a mouse tray Workplace Health and Safety Branch 8-9

11 City of Regina Safety Manual A Shorter Keyboard can help Figure 4 Computer keyboards come in many sizes. By using a shorter 35.6 cm or 14 inches in length keyboard instead of a standard 45.7 cm or 18 inches in length keyboard you will have an extra 10.2 cm or 4 inches of space at the side of the keyboard where the mouse can be placed (Figure 4). Advantages of a Shorter Keyboard The extra 10.2 cm or 4 inches gained by using a shorter keyboard will reduce the reach necessary to use the mouse. Fewer sideways movements mean you will be more comfortable and less likely to get injured. Disadvantages of a Shorter Keyboard A shorter keyboard means you will have to get used to a slightly different key arrangement, however, most people don't mind this as long as using the mouse becomes more comfortable. Workstation A workstation should allow the worker to sit in a balanced body position. Use a workstation that ensures that the alignment of the spine is the same whether the worker sits or stands. Use a workstation that allows the worker to move the spine freely. Use a workstation that can be adjusted to the needs of the worker Workplace Health and Safety Branch

12 Job Design Office Ergonomics A job design should allow the worker to work in a variety of balanced positions. Design tasks so they require movement of the spine and encourage the worker to alternate positions frequently. Avoid an excessive range of movement by: providing all materials at working level positioning tasks within easy reach avoiding lifting and transferring loads while sitting Avoid static positions. Position visual tasks that maintain the vertical alignment of the head and spine Design the lighting system to: provide good general lighting provide task lighting where necessary avoid glare Neutral Posture or a Balanced Position Gravity constantly exerts a downward force on our bodies. Parts of your body in contact with a supporting structure (the seat of chairs, armrests, floors, etc.) will feel pressure from the structure to balance this force. Parts of our bodies that are not in contact with a supporting structure will use muscles, tendons, and ligaments to balance the force of gravity with an upward force of their own. The body position that has the highest strength to handle the pressure felt by the supporting structure, while causing the least amount of strain on the muscles, tendons, and ligaments, is called the neutral or balanced body position. The following recommendations outline how to maintain a neutral body position while sitting: Hands, wrists, and forearms are straight, in-line and parallel to the floor. Head is level or bent slightly forward, forward facing, and balanced. Generally it is in-line with the torso. Erect or upright spine. Shoulders are relaxed and upper arms hang normally at the side of the body. Elbows stay close to the body and are bent between degrees. Feet are fully supported by the floor, or a footrest may be used if the desk height is not adjustable. Workplace Health and Safety Branch 8-11

13 City of Regina Safety Manual Back is fully supported with appropriate lumbar support when sitting vertical or leaning back slightly. Thighs and hips are supported by a well-padded seat and generally parallel to the floor. Knees are about the same height as the hips with the feet slightly forward. No twisting of the upper torso. No one seating position can remain comfortable over a long period of time. For this reason, multiple positions in which the body can be in the neutral position are recommended. As mentioned above, the workstation should allow the worker to adjust and move between these positions Workstation and Work Flow Design Seated manual tasks should be designed to maintain vertical alignment of the spine, and avoid constant stress on the shoulder region. This can be done by: Arrange work in a semi-circle Position tasks within easy reach Providing materials at or slightly below elbow height Providing arm rests where appropriate Avoiding tasks that require the shoulder or arms to be excessively high Avoiding tasks that require excessive reach. This guideline should be used with caution as the posture of each individual should be observed by a person with formal ergonomic assessment training as an example an Ergonomist or Safety Professional to ensure the body maintains its neutral position during the cycle of work. (Adapted from CSA ). General Guidelines for Work Reaches Primary Zone Usual work Secondary Zone Occasional work area Tertiary Zone Infrequent used working 8-12 Workplace Health and Safety Branch

14 Office Ergonomics Workstation Design for Foot Tasks Position foot tasks so that they can be done without twisting hips. Design foot tasks to avoid movement and exertion by only one leg. Provide the appropriate support for both working and non-working leg. Design a sitting task that encourages the worker to alternate positions frequently. Stretches for the Hands and Forearms 1. Start with your hand open. 2. Make a fist. Keep your thumb straight, not tucked under the fingers. Workplace Health and Safety Branch 8-13

15 City of Regina Safety Manual 3. Slide your finger tips up your palm so the tips of your fingers are near the base of your fingers and you should feel a stretch. Do not force your fingers with your other hand if something is painful. 4. With your hand open and facing down, gently bend wrist from side to side, as far as possible. Hold for 3 to 5 seconds. Repeat 3 times. 5. Start by stretching your arm and hand out and slowly rotate the wrist down until you feel a stretch. Hold for 3 to 5 seconds. Next, rotate the palm up until you feel a stretch. Repeat 3 times. 6. Grasp your hand and hold your fingers with the other hand. Slowly bend your wrist down until you feel a stretch. Hold for 3 to 5 seconds. Relax. Repeat 3 times. Then slowly bend your wrist up until you feel the stretch. Hold and relax as above Workplace Health and Safety Branch

16 Office Ergonomics 7. Sitting with your elbows on the table and palms together, slowly lower wrists to the table until you feel a stretch (your elbows will move outward a bit). Be sure to keep your palms together throughout the stretch. Hold 5 to 7 seconds. Relax. Repeat 3 times. Stretches for the Neck and Shoulders 1. Shoulder Shrug: The purpose of the shoulder shrug is to relieve early symptoms of tightness or tension in the shoulder and neck area. Raise the top of your shoulders towards your ears until you feel slight tension in your neck and shoulders. Hold this feeling of tension for 3 to 5 seconds. Then relax your shoulders downward into their normal position. Do this 2 or 3 times. 2. Head Glide: The head glide helps to stretch your chest, neck and shoulder muscles. Sit or stand upright. Without lifting your chin, glide your head straight back. You know you are doing this exercise right if it gives you the feeling of a double chin. Hold for 20 counts and repeat 5 to 10 times. Workplace Health and Safety Branch 8-15

17 City of Regina Safety Manual 3. Neck Relaxer: This exercise helps to relax the neck. Drop your head slowly to the left, trying to touch your left ear to your left shoulder. Repeat on the right side. Slowly drop your chin to your chest, turn your head all the way to the left, and then turn all the way to the right. 4. Shoulder Roll: This exercise will help relax the shoulder muscles. Slowly roll your shoulders backward five times in a circular motion. Next, roll your shoulders forwards. Stretches for the Back, Side and Legs 1. Back / Side Stretch: Interlace your fingers and lift your arms over your head, keeping the elbows straight. Press arms as far back as you can. To stretch your sides, slowly lean to the left and then to the right. In a similar way, you can also bring your arms in front of your body, or behind to stretch the shoulder blades and chest Workplace Health and Safety Branch

18 Office Ergonomics 2. Middle / Upper Back Stretch: Hold your right arm with your left hand just above the elbow. Gently push your elbow toward your left shoulder. Hold stretch for 5 seconds. Repeat with your left arm. 3. Ankle Flex and Stretch: Hold one foot off the floor with your leg straight. Alternately flex your ankle (point your toes up) and extend (point your toes down). Repeat with the other leg. 4. Leg Lift: Workplace Health and Safety Branch 8-17

19 City of Regina Safety Manual Sit forward on the chair so that your back is not touching the chair's back. Place feet flat on the floor. With a straight leg, lift one foot a few inches off the floor. Hold momentarily, and return your foot to the floor. Repeat with the other leg. 5. Standing stretch: When standing, keep knees slightly bent. Place your hands on your lower back and gently push your hands forward while leaning back slightly Workplace Health and Safety Branch