Editing Trackball (section)

== Ergonomics ==
[[File:Trackman marble wheel.JPG|thumb|[[Logitech]] TrackMan Marble Wheel designed to use the ball with the thumb]]

People with a mobility impairment use trackballs as an [[assistive technology]] input device. Access to an alternative pointing device has become even more important for them with the dominance of graphically-oriented operating systems. There are many alternative systems to be considered. The control surface of a trackball is easier to manipulate and the buttons can be activated without affecting the pointer position.<ref>{{cite news| url=http://www.axistive.com/alternative-pointing-systems-for-mobility-impaired-people.html| last=Dennis van der Heijden| title=Alternative Pointing Systems for Mobility Impaired People| publisher=Axistive| date=2006-03-15| access-date=2007-06-05| archive-date=2007-09-28| archive-url=https://web.archive.org/web/20070928044208/http://www.axistive.com/alternative-pointing-systems-for-mobility-impaired-people.html| url-status=live}}</ref>
[[File:Kensington TurboBall Mouse.jpg|thumb|A Kensington TurboBall Mouse designed to use the ball with the index or middle finger]]
Trackball users also often state that they are not limited to using the device on a flat desk surface. Trackballs can be used whilst browsing a laptop in bed, or wirelessly from an armchair to a PC playing a movie. They are also useful for computing on boats or other unstable platforms where a rolling deck could produce undesirable input.

Trackballs are generally either thumb-operated, with a ball about an inch in diameter or smaller moved by one digit (almost always the thumb) and the buttons clicked by others, or finger-operated, with a ball over two inches in diameter operated by the middle fingers and the buttons by the thumb and little finger. Users favor one format or another for reasons of comfort, mobility, precision, or because it reduces strain on one part of the hand/wrist. Most, but not all,<ref>For example, the [https://web.archive.org/web/20090916025144/http://www.logitech.com/index.cfm/mice_pointers/trackballs/devices/189%26cl%3DUS%2CEN Logitech Cordless Optical TrackMan] is finger-operated but asymmetric.</ref> finger-operated designs are symmetrical in design, making them [[ambidexterity|usable by both hands]], while thumb-operated designs are by their nature asymmetric or “handed,” allowing the smallest examples to be held in the air.  Thumb-operated trackballs are not generally available in left-handed configurations, due to small demand.

Some computer users prefer a trackball over the more common mouse for ergonomic reasons.  There seems to be no conclusive evidence from studies{{Which?|date=April 2018}} performed to determine which type of pointing device works best for most applications.  Application users are encouraged to test different devices, and to maintain proper posture and scheduled breaks for comfort. Some disabled users find trackballs easier since they only have to move their thumb relative to their hand, instead of moving the whole hand, while others incur unacceptable fatigue of the thumb.  Elderly people sometimes have difficulty holding a mouse still while [[double-click]]ing; the trackball allows them to let go of the ball while using the button.

At times when a user is browsing menus or websites rather than typing, it is also possible to hold a trackball in the right hand like a television remote control, operating the ball with the right thumb and pressing the buttons with the left thumb, thus giving the fingers a rest.<ref>{{Cite web |url=https://www.cdc.gov/od/ohs/Ergonomics/compergo.htm#MOUSE,%20TRACKBALL,%20OR%20OTHER%20INPUT%20DEVICE |title=Center for Disease Control web page about computer ergonomics |access-date=2017-09-17 |archive-date=2010-03-22 |archive-url=https://web.archive.org/web/20100322222204/http://www.cdc.gov/od/ohs/ergonomics/compergo.htm#MOUSE,%20TRACKBALL,%20OR%20OTHER%20INPUT%20DEVICE |url-status=live }}</ref>