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Risk Factors and Sources of Injury > Wrist Extension When Using the Keyboard          
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Animation Showing Ulnar Deviation on a KeyboardWrist Extension When Using the Keyboard

What is Wrist Extension?

The natural position of the hands with respect to the relative vertical position at the wrist is along the plane or below it (i.e. one should attempt to have the tips of the fingers at the same height as the wrist or preferably slightly lower). When the hand rises above this plane (i.e. making the hand signal for 'STOP'), this is called wrist extension. This greatly reduces blood flow through the wrist and can quickly cause pain, fatigue and numbness.

Most keyboards have a built-in positive inclination (i.e. the Function row is higher than the space bar).  In addition, there are often 'feet' at the back of the keyboard which further increases this positive incline, forcing the user into a posture of Wrist Extension.

Why is Wrist Extension a Risk Factor?

When adopting this position, blood flow is constricted through the wrist and this posture also requires sustained muscle tension which further reduces blood flow to the muscles. The median nerve runs through the carpal tunnel in the wrist, and when adopting a position of Wrist Extension the span of this tunnel is compressed and pressure on this nerve can lead to Carpal Tunnel Syndrome

How Much Wrist Extension is 'ok' and not a Risk Factor?


For most individuals, even a minimal amount of Wrist Extension will cause some discomfort and is a potential risk factor.

What are the Symptoms of 'too much' Wrist Extension?

Symptoms of excessive Wrist Extension include pain in the top of the forearm and to a lesser extent in the wrist itself.  In more significant cases, this can include pain, numbness or tingling in the fingers and weakness in the hand and fingers.

How can the Choice of Keyboard Help to Reduce Wrist Extension?

Neutrally and Negatively Inclined Keyboards feature an architecture and housing which is either neutral or even negative (i.e. the plane of the keys is level or declines when moving from the front (space bar) of the keyboard to the rear (function keys) of the keyboard. 

What Other Strategies can be used to Reduce Wrist Extension?


Many Articulating Keyboard Arms offer the option of a negative inclination, which will make the entire work surface slope away from the individual, ensuring that the hands are not bent upward at the wrist, even if the keyboard has a positive inclination.  Ensuring the proper height of the workstation i.e. that it should be slightly lower than the underside of the forearm / elbow is critical in prevention Wrist Extension.

Often individuals will adopt positions of Wrist Extension while they are asleep (without realizing it).  The wearing of a wrist brace or support while sleeping can prevent accidental adoption of a position of Wrist Extension when one is supposed to be at rest.

 

Last edited December 16th, 2013

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