How can repetitive strain injury be avoided when using a computer?
PostureIn the 1980s, the ideal working posture at a computer workstation was considered to be sitting upright, with hips, knees and elbows at 90 degrees, no arm support and feet flat on the floor. However, today there is growing evidence that this posture is less than ideal. In fact, it appears that there is no ideal posture or setup that is applicable to all people, but that equipment needs to be adjustable within a range in order to allow for individual differences. Instead of adopting just one posture, you should try sitting in different safe positions and as well, make sure to take breaks and carry out a variety of tasks. Actually, even when people are ‘set up’ to work in an upright posture, they rarely stay that way for long periods. Most people prefer to lean back in their chairs at angles of 100- 120 degrees rather than sit upright. This more relaxed posture has a number of benefits, including less disc pressure in the spine and relaxation of the back muscles. Another alternative to upright posture is the forward tilting seat, which maintains the spine in a position similar to standing (thereby reducing pressure). However, there has been criticism of this approach because people tend to put weight on the legs, which can cause discomfort. This posture also means that people vary their position less, which can result in discomfort and strain. Overall, it appears that different postures are best suited to different tasks. Touch typing is helped by a traditional upright posture, while reading and writing is suited to the forward tilt posture. When mostly screen work is required, the back tilt posture to be most suitable. The chairChairs are becoming more adjustable, allowing people to change settings to suit their size and preferences. However, studies have shown that many people do not change the basic settings on desk chairs, perhaps because they are so difficult to adjust! You ought to make sure you know how to adjust your desk chairs to suit the task you are doing and ensure you are comfortable. Other chair typesThe kneeling chair has been criticised because it’s a difficult to get on and off, as well as constraining the legs. However, it may be appropriate for people with jobs other than computer work, such as dentists or hairdressers. Fitballs or Swissballs are becoming increasingly popular, however there’s no evidence demonstrating their effectiveness in reducing injury or discomfort. Some ergonomists are concerned about the instability of these balls and the possibility of fatigue from sustained leg muscle exercise. The MonitorHeightThere’s little consensus regarding correct monitor height. Recommendations range from 15 degrees above, to 45 degrees below eye height. Most recommendations are for a high monitor position, which aims to prevent a forward head tilt, which is fatiguing after long periods. So a high monitor position reduces muscular load on the neck by maintaining a neutral head position. However, the high monitor position can also cause increased stress for the eyes. In other words, the gaze angle required by a high monitor is likely to either cause eye strain and discomfort, or cause the user to adopt postures that cause muscle discomfort. The opposite extreme is low monitor height. There is some evidence that a low monitor position causes increased forward tilt of the neck, which may result in fatigue, discomfort or headaches. However, many people are more comfortable with a low monitor position, and therefore adopt a more relaxed posture when set-up in this way. You should monitor adjust the set-up according to your own comfort and preferences. DistanceThe correct distance of the monitor from the user is dependent on a number of things such as age and visual capacity. If the monitor is at a lower height, it can be placed closer to the user. However, the closer the monitor, the more visual strain it may cause and recommendations are for a distance of 500mm or more. The KeyboardPositionTraditionally, the keyboard was positioned close the edge of the desk, with a ‘floating’ posture (unsupported) for the hands. However, recent studies have shown that distances of more than 120mm from the edge of the desk to the home row of keys are associated with a lower risk of hand and arm symptoms. This finding is perhaps because people support their forearms on the desk when the keyboard is a greater distance from the edge of the desk. Supporting the arms on chair arm rests also reduces musculoskeletal symptoms. However, if only the wrists are supported on the desk (most common when the keyboard is close the edge), this increases carpal tunnel pressure and RSI symptoms. Therefore, placing the keyboard more than 120mm from the desk edge seems to be a good idea. Alternate keyboardsA variety of alternate keyboards have been designed to minimise the hazards of computer use. However, they don’t all work well: Firstly, the negative slope keyboard (which rakes the base of the keyboard away from the user) is intended to neutralise wrist posture. However, studies have shown that it has the potential to increase wrist extension and reaching of the tendons, as well as keeping users in one fixed position (not a good idea!). Negative slope keyboards are therefore not recommended. The Microsoft Natural keyboard has been found to improve wrist extension and decrease forearm muscle activity. In a study with overuse injury sufferers, use of this keyboard instead of a standard keyboard resulted in an improvement in pain severity and hand function over six months. However, some users just did not like this keyboard and those who did like it tended to get better results. The Kinesis keyboard results in the lowest degree of wrist extension of any keyboard tested, as well as significantly less muscle activity in the fingers during both resting and typing. However, there are some concerns about productivity with its use – even after 10 hours of training with this keyboard, users are still unable to reach their average typing speeds on a standard keyboard! The Comfort keyboard is associated with less repetitive movement in typing, particularly in females. However, the depth of the keyboard is a problem, as users are unable to rest their forearms on the desk surface. Wrist RestsThe primary purpose of wrist rests designed for keyboard use is to maintain a neutral wrist position while keying. These vary in terms of width, thickness and compressibility, and are often integrated into or attached to the keyboard itself. Unfortunately, while wrist position may be improved, using wrist rests during typing is associated with less movement, increased tendon strain and greater intracarpal tunnel pressure. This is particularly true of softer, more compressible wrist rests. Using wrist rests during micro-breaks, rather than while keying, was not harmful in these studies. Many people prefer to place wrist rests under the forearm, and this seems to improve wrist position. The DeskEveryone agrees that desk height should be adjustable, as the best desk height is related to the height of the user. Each individual user should adjust their desk to at, or slightly below, their elbow height. Preferred heights vary from 580mm to 850mm, therefore adjustability ought to cover as much of this range as possible. There’s little research on the benefits of curved or shaped work surfaces, or those that have an extension on the side of the mouse side, but initial studies indicate that these may provide better support. Keyboard trays and split desks often leave little room to use a mouse and most importantly, mean that users have less choice in how to use their workspace. As well, the adjustment mechanisms of these devices may be dangerous to the knees and/or leave less room for the thighs. As it’s vital to be able to change your posture to prevent injury, these devices are not recommended. The MouseThe mouse is the most commonly used input device for computers, accounting for two thirds of computer operation time in the average user. However, the mouse has, in many studies, been associated with discomfort and strain in the shoulder and neck. The further the mouse was placed from the keyboard, the greater the number of neck and shoulder symptoms users reported, and the vast majority of computer users place the mouse too far to the right of the keyboard. The lowest levels of muscle activity were found when a keyboard without a numeric keypad was used, as this allows the mouse to placed directly in front of the right shoulder. What the mouse is used for is also very important. Carpal tunnel pressures are greatest during repeated dragging tasks, when compared with simple pointing tasks. A scroll-ball mouse is a good idea because it minimises dragging. Using a mouse either forcefully or repetitively can be a risk factor for overuse injuries. It is extremely important to take micro-breaks when mousing, as continuously activating the neck and forearm muscles may lead to musculoskeletal symptoms. Stress is also worth thinking about. If users are required to pay more attention, concentrate harder, increase their speed or increase their accuracy, the result is increased heart rate, blood pressure, and, most importantly, muscle activity. The lower the muscle activity, the safer the user! This means that employers should be aware of the dangers of putting unreasonable pressure on their employees. In fact, everyone should be aware of the dangers of being hurried and stressed when using a computer. Mouse size and shape varies a lot, but little research has been carried out on the benefits of various designs. What feels comfortable for you and the size of your hand are important in choosing a mouse. However, be aware that there is evidence that a very large mouse may cause hand pain. Using a wrist or arm rest to support your forearm during mouse use has been shown to minimise extreme postures of the shoulder in some studies, so these seem to be a good idea. Mouse AlternativesThe trackballThis is a ball or surface placed in the middle of keyboard. Compared to the mouse, the trackball has been associated with decreased muscle activity in the forearm and shoulder, as long as there is forearm support. Finger activity is greatly increased, but this is generally less of a risk for developing overuse injuries. For some users, however, forearm muscle activity was increased and wrist extension was greater than during mouse use. The limited research into trackballs means that it’s hard to give a recommendation, although they offer an alternative for people with an overuse injury from conventional mouse use. It is clear, however, that the closer the device is to the centre of the keyboard, the better, and that forearm support should be used. The upright mouseThis mouse design appears to neutralise forearm posture and lessen muscle activity, particularly when combined with forearm support. A study found that using an upright mouse for six months resulted in a significant decrease of neck, shoulder and forearm pain in users, so it can be recommended for people with an overuse injury and other mouse users. Overall, the research shows that the most important feature of office equipment is adjustability. Users also need to be taught how and when to adjust their equipment. If you feel uncomfortable using a particular product, stop using it immediately and look for an alternative. Most importantly, don’t think that just because a product is called ‘ergonomic’ that it will necessarily be good for you! While you’re here…While you’re here, how about helping us out with a donation? We’re a really small organisation doing a really big job. We give people with RSI across Australia the info they need to get the right treatments, navigate the worker’s compensation system and better manage
daily life. How can you prevent repetitive strain injury when using a computer?10 tips for avoiding RSI at your computer. Rest your feet flat on the floor. ... . If you have a curved desk, sit central to the curve.. Place your screen at eye level and directly in front of you.. Position your keyboard directly in front of you, with a space at the front of the desk to rest your wrists when you are not typing.. How can using computers lead to repetitive strain injury?Slouching at a desk or keyboard puts your spine and limbs in positions that contribute to increased strain and tension, as well as increasing the risk of eye strain. OFFICE SETUP: A poorly designed workstation, or one that does not fit you well, can contribute to the onset of repetitive strain injury.
|
