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Choosing a mouse for specific ergonomic needs can be confusing and overwhelming, given the numerous available options. For many people, a standard computer mouse will suffice. If you are comfortable using a standard mouse and if there are no health concerns to consider, you may choose to stick with your standard mouse and avoid trying to solve a problem that doesn't exist. However, if you just feel uncomfortable with a standard mouse or if you are looking for a replacement due to a specific health need, then you will definitely want to explore all the options. This discussion will focus on the four main types of computer mice – standard, vertical, trackball and central.
A standard computer mouse is the ubiquitous mouse that you will see at 90% of computer workstations. Most of the time this type of mouse is adequate for the person using it. A standard mouse is designed to hold your hand in a natural position with slight flexion in the fingers, so that holding the mouse only requires a soft cradling of the mouse with the hand. However, if the mouse is too small, too large or the wrong shape, the grip goes from being gentle and easy to uncomfortable and forced. For example, if the mouse is too small for the user, the hand ends up in a claw-like posture in order to hold the mouse, exhibited by over-flexion of the fingers. This type of grip may cause muscle spasm in the finger flexors of the forearm and hand. Likewise, a mouse that is too large for the user causes the muscles in the hand to have to work too hard for the grip because they are not optimally positioned (the muscles are working from a lengthened position thus creating a mechanical disadvantage in the muscles). This too may result in cramping or hand pain. Often identifying the right size mouse is simply a matter of trial and error (it will just feel right), and most standard mice will be suitable for most people. Some manufactures will offer different size options within their mouse lines and identifying your size might be necessary. The commonly accepted sizing method is to measure the distance from the crease in your wrist to the tip of your middle finger, which for many of us is somewhere around 7”. Seeing as every manufacturer uses different design criteria, there is no universally accepted range (each manufacturer will offer their own sizing guides) but it is reasonable to go with the strategy that if you measure between 6½”-7½” then you should be using a regular size mouse. If this measurement is less than 6½” then you should be looking at a small mouse and if this is greater than 7½” you should be looking at a large mouse. [Important note: a 'travel' mouse is not the same as a 'small' mouse. Yes, a travel mouse is small, but these are especially small because they are designed primarily to fit easily into a bag and to take up less space. A small size standard desktop mouse will generally be larger than a travel mouse but smaller than a regular sized mouse].
A simpler but perhaps less accurate method of sizing a mouse is to place your hand on the mouse starting at the wrist area, so that the base of your hand (the point between those two bony prominences at the front of your hand near the wrist) is at the very front of your mouse. Then proceed to lay the rest of your hand and fingers over the mouse. Your fingertips should come close to the far end of the mouse but should not touch the desk. If your fingers do touch the desk the mouse may be too small for you. If your fingers do not come near the desk at all, the mouse may be too large.
As mentioned above, sometimes a standard mouse is not the ideal mouse, either because it doesn’t feel right or for a specific health requirement. In the following paragraphs, I will discuss the alternative mouse options and the rationale for each.
A vertical mouse is designed to put the hand in a position whereby the front of the wrist does not face the desktop. This may be a good idea if there are symptoms or conditions that arise from pressure or contact at the front of the wrist, such as carpal tunnel syndrome, or conditions that limit pronation of the wrist (pronation is the motion of rotating your right wrist counter-clockwise or your left wrist clockwise; when your hand is oriented palm down your wrist is considered to be in a pronated position. Conversely, the palm-up position is called supination). If you are experiencing pain at the front of the wrist that seems to be because of pressure of the front of the wrist against the mousing surface, or if you are unable to easily pronate the wrist, a vertical mouse may be something to consider. The mouse pictured here is a semi-vertical mouse, although there are also true vertical mouse options, where the hand is positioned with the thumb facing straight up. Whether you opt for a semi-vertical mouse or a true vertical is really up to you, as the main purpose for choosing a vertical mouse is to get the front of the wrist off the mousing surface and / or to reduce pronation, which even a semi-vertical mouse will accomplish. Some people choose to use a vertical mouse not because of the presence of symptoms per se, but rather because it 'just feels right'. It is interesting to note that when using a full vertical mouse, the wrist is actually in it's true anatomical neutral position; when using a standard mouse the wrist is 90-degrees off from neutral (properly described as 90-degrees pronated).
Click here for a more in-depth review of the Contour Unimouse
A trackball mouse frees you from having to actually grip or hold the mouse during use and the mouse casing stays in one position on the desktop. Rather than move the mouse around the desktop to move the cursor, like you would with a standard mouse, you move the cursor by rolling a ball housed within the mouse casing. [I only recommend using central trackballs, like the one pictured here, and not thumb trackballs. This discussion pertains to central trackballs. More on this later]. The primary reason for using a trackball mouse would be to free the user from having to continuously grasp the mouse. This is particularly beneficial if you are suffering with hand cramping from prolonged gripping, or arthritis in the hand and fingers. For arthritis in particular, use of a trackball mouse can actually be therapeutic as the trackball mouse requires the user to move the hand and fingers a lot during use, as opposed to use of a standard mouse which requires very little movement of the hand and fingers (with a standard mouse the movement comes more from the wrist and arm to move the mouse whereas the hand itself does not move much at all). Movement is the best thing for arthritic joints, which is why use of a trackball mouse is generally a good option for anyone suffering with arthritis in the hand or fingers. Another reason why one might choose to use a trackball mouse like the one pictured is if there is tendinitis of the index or middle finger, which may occur as a result of the small repetitive movements required from constant clicking of the left and right mouse buttons on a standard mouse or from repetitive use of the scroll wheel. Using a trackball mouse like the one pictured requires the user to use the thumb for the left button and the ring and / or pinky fingers for the right mouse button, thus shifting the burden away from the index and middle fingers. The scroll wheel on this mouse is a ring around the ball which is moved by rotating it with the thumb (counter-clockwise) and the ring and / or pinky fingers (clockwise).
As mentioned above, I generally do not recommend the type of trackball mouse that requires the thumb to operate the trackball. When using a thumb trackball mouse the hand tends to remain quite static and most of the movement comes only from the thumb. Continuous circumduction of the thumb (the circular movement required to operate this type of trackball) significantly increases the risk of developing tendinitis of the thumb.
A central mouse puts all the operation control, as the name implies, at the central area of the workstation rather than to the side. This mouse sits directly in front of the keyboard within easy reach of the user. One benefit to having the mouse controls at the central area is with respect to arm positioning. When using a standard mouse the mouse arm tends to be abducted or externally rotated away from the body because the mouse is to the side of the keyboard. This posture of the shoulder joint away from neutral increases the risk of sprain / strain type injury to the shoulder joint, shoulder girdle and upper back. This is particularly pronounced for right-handed individuals because of the design of the standard keyboard. On a standard keyboard the navigation keys and the numeric key pad are on the right side; therefore, the mouse tends to be positioned quite far to the right. Left-handed individuals are able to position the mouse so it is not quite as far away from the neutral area, as there is no competition for desk space with the navigation keys and numeric key pad. A central mouse, therefore, tends to be perhaps of greater benefit for right-handed users as the gains in arm position are more pronounced than for left-handed users. Another benefit of having the mouse controls centrally located is that it allows for two-handed mouse use. For anyone suffering with symptoms in the wrist or hand such as carpal tunnel syndrome or tendinitis, the advantage of being able to shift some of the mouse operations to the other hand could give the injured hand just the rest it needs to recover. This is not a full switch of mouse use to the non-dominant hand, as you would still be using your dominant mouse hand for mousing, it's just that the non-dominant hand can be used to help share the work load to some degree.