Vertical mice are grasped in a ‘handshake’ position. This position keeps the wrist from bending as much to the side while the forearm also turns inward to a lesser degree. In other words, using a vertical mouse decreases ulnar deviation and pronation (Schmid, et al., 2015). This means that muscle activity in the forearm is less than it would be when using a conventional mouse (Quemelo & Vieira, 2013). This results, especially with intensive use of the mouse, in a high degree of comfort and ensures that the wrists, arms and shoulders are kept in a relaxed position.
Research has shown that the use of a vertical joystick mouse ensures a faster recovery of forearm, wrist and hand complaints (Aarås, et al., 2001). A vertical mouse also prevents RSI complaints because it puts less strain on the shoulders, arm and wrist.