Benefits of a central mouse:
- May help reduce shoulder strain as it allows for central positioning of the arms
- Allows you to use two hands for mousing which may reduce symptoms relating to over-use of one hand during single hand mouse use
- Allows you to avoid grasping which can reduce hand cramping or muscle spasms
- Less dependency on single digits (i.e. index and middle finger) for mouse click functions
A central mouse is positioned in front of the keyboard with the functional parts of the mouse (cursor movement bar, mouse buttons and scroll wheel) directly centred to the user. This mouse provides two significant benefits: it allows you to place your hands directly in front of your body in the central position, rather than off to the side as you would normally do with a standard mouse; and it allows for two-handed mouse use.
When using a standard mouse the mouse hand is positioned to the side of the keyboard. For the majority of the population who are right-handed, this typically requires abduction and / or external rotation of the right shoulder (i.e. the arm is moved away from the body to reach the mouse, as you can see in the picture to the right). The reason this is particularly pronounced for right-handed users has to do with the design of the keyboard. The 'primary' keyboard consists of the alphabet keys, the row of numbers at the top and the function keys. The 'secondary' keyboard, situated to the right of the primary keyboard, consists of the navigation keys and the numeric key pad. Proper positioning of the keyboard means you should be sitting centred to the primary keyboard. Therefore, the G-H keys should line up with the midline of your body as these keys represent the centre of the primary keyboard. However, with the keyboard centred to your body this way, the presence of the secondary keyboard forces the right hand quite far to the right in order to access the mouse. Prolonged positioning of the right arm in this manner is a very common cause of shoulder strain and periscapular pain (upper back area adjacent to the edge of the shoulder blade). If you suffer with predominantly right shoulder girdle / right side upper back pain that tends to be worse with mouse use, this may very well be the reason why. Luckily for left-handed users this is not an issue, as the keyboard does not extend as far to the left side and the mouse can be positioned closer to the midline with the left arm positioned closer to the body.
Use of a central mouse allows you to keep your hands centred in the midline area thus completely eliminating abduction and external rotation of the right arm when using the mouse. With the mouse hand in the central area the elbows are at your sides and the arms are internally rotated, which is a much healthier shoulder position. As you can see, use of a central mouse such as the Rollermouse also has the benefit of allowing you to use both hands for mousing. This can help to reduce overuse of the mouse hand which can often lead to repetitive strain or cumulative trauma related symptoms.
Arms are internally rotated when using a central mouse
Yet another benefit of using a central mouse is that you do not need to grip or hold a mouse. Keeping the hand loose and open may reduce the incidence of cramping or muscle spasm in the hand.
The Rollermouse Red is an incredibly well-designed product. The Rollerbar, which moves the cursor, is made up of a rubber cylinder with tactile bumps along it to so that even a gentle touch of your finger(s) will easily move the bar. This rubber cylinder moves along a thinner but longer metal cylinder which allows for seamless movements back and forth and side to side. Cursor movement is extremely responsive and simple. There is a small button just in front of the Rollerbar that allows you to choose from ten different cursor speeds. Just under that button there is a perfectly sized scroll wheel. To the left and right of the scroll wheel are the left and right mouse click buttons. Underneath the scroll wheel there is a double-click button (i.e. one click of this button responds as a double-click of the left mouse button). Just above the left and right mouse click buttons are the single-click 'copy' and 'paste' buttons. Repetitive mouse clicking is a common cause of tendinitis so using single-click functions to double-click, copy and paste can be very helpful in reducing overall mouse clicks and therefore reducing the likelihood of developing conditions related to repetitive actions, like tendinitis. Furthermore, the mouse clicks on the Rollermouse are less deliberate. When using a standard mouse your hand is in a fixed position on the mouse and the index and middle fingers need to make a very deliberate downward motion to click the respective mouse buttons. This results in repetitive small flexion-extension movements of the fingers. Small repetitive movements are the cause of repetitive strain injury and cumulative trauma disorder, whereas broader and unique movements are healthier. When using the Rollermouse, you may use different fingers for the same function (i.e. sometimes I will press the left mouse click button with my thumb, other times with my index finger and other times with my middle finger) which helps to spread the work load, and the hands are not fixed to the device so the movements are less deliberate.
The one caveat with the Rollermouse, as with any central mouse device, is that the keyboard must be positioned further from your body than you otherwise might place it, as the mouse must be situated in front of the keyboard***. This is obviously an inherent issue and is unavoidable given the design of this mouse. In my opinion, the many benefits of this mouse far outweigh this one issue. That being said, if the nature of your work is that you are primarily typing and mouse use is minimal, then this might not be the most practical device for you. However, if you are a moderate to heavy mouse user, the Rollermouse Red is definitely worth a look. Furthermore, if you experience right shoulder and / or upper back pain when using a standard mouse due to lateral reaching with the right arm, then you should seriously consider a central mouse option such as the Rollermouse.
***Addendum***
Contour has recently released the Rollermouse Mobile, which appears to have all the great functionality of the Rollermouse Red, but with a reduced profile (depth of 2.2" for the Mobile vs 3.95" for the Red). This would allow you to bring the keyboard closer to your body and thus avoid having to reach too much toward the keys. Looking forward to reviewing this exciting new product!