The best location for a mouse is on a platform just above the keyboard's number pad. It can also be placed on an angled platform to the side of the keyboard.
If you are a full-time laptop user, you should place you laptop on a rise so that the screen is at eye-level. Use an external mouse and keyboard to prevent wrist deviation and overreaching.
Whatever input devices you choose to use, position the device comfortably and ensure that your wrist is in a neutral position when using it.
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.
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 user - 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 user - If you use your laptop at work as your main computer:
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. If you plan on using a laptop as your primary computer, you may want to consider using an external, full-size keyboard to reduce ulnar deviation (outward bent wrists).
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.).
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 rest your wrists on a hard surface. Placing your wrists on a hard surface (especially corners) greatly increases the pressure inside the carpal tunnel, causing it to become inflamed. This inflammation can lead to chronic pressure and pain on the median nerve, which supplies feeling and movement to parts of 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. This encourages mouse movement by flicking the wrist, which can increase pressure on the carpal tunnel.
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.