• Laptops
• Mice

Laptop Computers and Ergonomics

The design of laptops violates a basic ergonomic requirement for a computer, namely that the keyboard and screen are separated. In the early days of personal computing, desktop devices integrated the screen and keyboard into a single unit, and this resulted in widespread complaints of musculoskeletal discomfort. By the late 1970s a number of ergonomics design guidelines were written and all called for the separation of screen and keyboard. The reason is simple: with a fixed design, if the keyboard is in an optimal position for the user, the screen is not, and if the screen is optimal, the keyboard is not in an optimal position. Consequently, laptops are excluded from current ergonomic design requirements because none of the designs satisfty this basic need. This means that you need to pay special attention to how you use your laptop because it may cause you problems. Consider the following tips when choosing and using a laptop computer.

What Type of Laptop Computer User Are You?

Using a laptop is often a tradeoff between poor neck/head posture and poor hand/wrist posutre. Are you and occasional user who works on your laptop for short periods of time, or are you a full-time user with the laptop as your main computer? While occasional users will have less risk of problems than full-time users, every laptop user should pay some attention to how they use their laptop.

Occasional Users - Because the neck/head position is determined by the actions of large muscles, you are better off sacrificing neck posture than wrist posture. For occasional use, you should:

• find a chair that is comfortable and allows you to sit back

• position your laptop in your lap for the most neutral write posture that you can achieve

• angle the laptop screen so that you can see this with the least amount of neck deviation.

Full-Time Users - If you use your laptop at work as your main computer:

• position your laptop on your desk or work surface in front of you so you can see the screen without bending your neck (you may have to elevate the laptop off the desk using a stable support surface such as a computer monitor pedestal)

• use a separate keyboard and mouse (connect the keyboard and mouse directly to the back of the laptop or to a docking station)

• use the keyboard on a negative-tilt keyboard tray to ensure a wrist-neutral posture

• use the mouse on an adjustable-position mouse platform.

Laptop Dimensions

Many laptops offer large screens (15" plus) and can work as desktop replacements (giving the viewing area of a 17" monitor). However, think about where you will most use your laptop to help you choose the best size. The larger the screen, the more difficult it will be to use this in mobile locations (e.g. airplane, car, train). There are a number of smaller notebook and ultra-portable laptops on the market. Consider issues of screen size and screen resolution. A small screen (e.g. 12.1") will be useful in mobile settings, but if the resolution is high (e.g. XGA 1024 x 768) make sure you can read the screen characters and can easily use the input device to point to areas on the screen. The smaller the laptop, the smaller the keyboard, so make sure that you can comfortably type on a keyboard that may be only 75% the size of a regular keyboard.

Laptop Weight

If you will be frequently transporting your laptop, think about the weight of the system. The system includes the weight of the laptop plus the required accessories (e.g. power supply, spare battery, external disk drive, zip drive, CD-RW drive, etc.). Many lightweight portables can become as heavy as regular laptops when you add the weight of all the components together. If your laptop and components weigh 10 lbs. or more, consider using a carry-on bag that can be pulled along. If you want a smaller bag and can comfortably carry your laptop, there are many good shoulder bag designs available.

Ten Tips for Using a Computer Mouse

The following tips should help you avoid a mouse-related musculoskeletal injury. The same posture principles apply to other input devices (e.g. trackball, touchpad, pen, digitizing puck, etc.). For more information, contact the risk management office at x2706.

1. Mouse grip. Hold the mouse gently to move it over a mousing surface.

2. Mouse from the elbow. Avoid skating or flicking the mouse with your wrist. Make controlled mouse movements using your elbow as the pivot point and keep your wrist straight and neutral.

3. Optimal mouse position. Sit back in your chair, relax your arms, then lift your mousing hand up, pivoting at the elbow, until your hand is just above elbow level. Your mouse should be positioned somewhere around this point. When possible, do not use a mouse by stretching to the desk or out to the side of a keyboard. With a flat mouse platform, position this 1-2" above the keyboard and over the numeric keypad if you are right-handed - you can easily move it out of the way if you need to access these keys. With a downward-sloping mouse platform, position this close to the side of the keyboard so that you can use the mouse in a neutral wrist position.

4. Protect your wrist. If you look at the anatomy of the wrist it is curved away from any contact surface (you can easily see this by resting your hand/arm on a flat surface - you'll see light under the wrist and can probably even pass a thin pen under this). The forearm is shaped like this for the wrist to remain free of surface pressure contact.

5. Avoid restricting circulation. For many people, there are exposed blood vessels near the skin at the wrist, which is where the pulse is often taken. Any pressure in this region will disrupt circulation into the hand and this will increase the risks of injury.

6. Do not use a wrist rest. Research has shown that using a wrist rest doubles the pressure inside the carpal tunnel, because the floor of the tunnel is a more flexible ligament that transmits external pressure changes directly into the carpal tunnel (the roof of the tunnel is bone so the pressure does not get transmitted on through the hand).

7. Avoid restricting arm movement. With a softly-padded wrist rest, especially one that is rounded, or a soft chair arm rest, the forearm becomes "locked" into position and this encourages people to make mouse movement by flicking the wrist, which also increases intracarpal pressure.

8. Keep the mouse free-moving. The base of the palm of the hand is the part of the body designed to support the hand when resting on a surface. For keyboard use, a broad palm support is best. However, mouse use is different from keyboard use. With a keyboard, the best posture is for users to float their hands over the keyboard when typing and then to rest on the palm support in micro-breaks between typing bursts. With mousing this doesn't happen. A mouse is used by moving its location over a surface, and resint gusually occurs when mouse movements stop but with the mouse still being held in the hand. Mouse movements should be made using the elbow as the pivot point, not the wrist. Anything that impairs free movement of the forearm/hand and mouse will increase injury risks.

9. Mouse shape. Try to choose a mouse design that fits your hand but is as flat as possible to reduce wrist extension. A symmetrically-shaped mouse is usually preferred to a curved mouse. Consider a larger mouse, that encourages arm rather than wrist movements.

10. Load sharing. If you want to load share between your left and right hands (that is, use the mouse for some of the time with each hand), choose a mouse platform that can be easily configured to the left and/or right, and a symmetrically-shaped mouse that can be used by either hand.

Other Input Devices

Whether you choose a different mouse design, a trackball, a joystick, a pen, a touchpad, or some other input device, make sure that you position this comfortably, and that your wrist is in a neutral position when using the device.

Summary Recommendations

• The best arrangement for a mouse is a platform over the number keypad and just above the keyboard.

• A good arrangement is a pad on an angled platform to the side of the keyboard.

• A poor arrangement is a flat surface to the side of the keyboard.

• The worst arrangement is on the desk out to the side of the keyboard.