Trackball Mice Information Page
Standard Mice
Standard mice require wrist and arm postures which can contribute to hand wrist and forearm irritation. Over time, this irritation can lead to discomfort or a repetitive strain injury.
| The characteristics of operating a standard mouse include: | |
| Static grip: the mouse is held, usually with the thumb on one side and the fourth and fifth digits on the other. This grip is static as it is the only way to move or stabilize the mouse. |  |
| Wrist pronation (palm down): the forearm must be turned so that the wrist is facing palm down, a position known as pronation. As with the static grip, pronation must be maintained if you want to move or click the mouse. |  |
| Clicking: primarily by the index (second) finger and occasionally by the middle (third) finger. This clicking is repetitive and done while maintaining the static grip and pronation. |  |
| Coordination: the hand holding the mouse must be kept steady while clicking. For persons with coordination or visual acuity issues, stabilizing the mouse to select something on the screen can be very difficult. Double clicking can be even more difficult. |  |
Trackballs
A trackball is a stationary mouse, which refers to the fact that the mouse pointer is moved by manipulating the ball, not by moving the mouse on the desk surface. Consequently, a stationary mouse does not need to be held in order to move the pointer. The static grip is eliminated, reducing wrist stress.
There are many designs of trackballs, some with a centrally located ball and others that oblige the operator to use one digit – usually the thumb. I recommend trackballs with a centrally located ball as this allows the ball to be manipulated by any finger, part of the hand, or, in some cases, the feet. Trackballs that force the operator to use just the thumb can contribute to discomfort of the thumb joints.
| A centrally located ball allows the trackball to be operated in an ambidextrous manner, using either the left or right hand to move the ball and click the buttons. |  |
While many trackballs are designed to be moved with the wrist pronated, the reality is that a trackball with a centrally located ball can be used with the wrist in any position.
| Moving the ball with one or more fingers. |  |
| Moving the ball with a the palm of the hand (fingers are not used to move the ball). |  |
| Moving the ball with the wrist held in the anatomically neutral “handshake” position, with the ball being moved by the little finger side of your palm (the hypothenar side). |  |
The trackball allows the operator to separate mouse moving and clicking functions. After moving the pointer to the desired screen location the operator can let go of the ball and then click the appropriate mouse button.
| Clicking can be accomplished without having to hold the mouse or the ball, and can be done with any finger. |  |