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Risk Factors and Sources of Injury > Pronation or Working with the Hands 'Flat' on the Worksurface          
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Animation of Pronation of HandPronation or Working with the Hands 'Flat' on the Worksurface


What is Pronation?

Pronation refers to the twisting of the hand and forearm to a fully 'palm down' orientation.  When the hands and forearms of an individual are flat on a desk they are working at, they have fully 'pronated' their hands and forearms.  This position is not the neutral, relaxed posture of the hands when performing an immediate task (i.e. working on a conventional 'flat' keyboard or 'flat' mouse when at a desk).  For most individuals, the posture that is most comfortable is somewhere between 10° from the horizontal (i.e. with the thumb side of the hand higher than the little finger) and a vertical or 'handshake' position (i.e. 90° from the horizontal).  Every individual has a different range and size of comfortable postures that arises from their own physiology, conditions and injuries they have sustained. 

Why is Excessive Pronation a Risk Factor?

When an individual is forcing his hands to pronate to maintain in full contact with the input device, this puts a static load and strain on the joints, muscles and membranes in the arm which can lead to fatigue, discomfort, pain and injury.  Just as excessive pronation is something that individuals seeking to reduce the risk of injury should avoid, excessive Supination can be an equally significant risk factor.

What is the 'Best' Angle to Position the Hand and Forearm?

As indicated earlier, every individual is unique and for some, a near vertical posture will be most comfortable while for others a near horizontal posture will be ideal.  Unfortunately, there is no 'best' angle, and there are multiple considerations as what may be the best angle for the elbow may not be for other muscle groups (e.g. the fingers).  For keyboarding, the tradeoffs of increasing the angle beyond 20° typically make this the maximum viable angle to ideally position the keyboard for most users (see Why Does Vertical Mousing have Less Drawbacks than Vertical Keyboarding).  For mousing, there are less tradeoffs in moving to a more vertical posture, which makes many mice up to 30° viable options for many users. 

How can a Keyboard Help to Reduce Pronation?

Keyboards which have a profile or design that allows the keys to be physically higher in the center will result in a posture which is less pronated (commonly called a 'thumbs up' posture, as the thumbs are now higher above the work surface than the little fingers).  Adjustable Keyboards which offer the ability to 'tent' or incline to the desired angle of the user will greatly assist in the prevention of excessive pronation while keyboarding.  Some Fixed Split Keyboards also have a non-adjustable fixed inclination which, if it happens to be the angle the user is seeking and meets their other needs, would also serve this purpose.

How can a Mouse Help to Reduce Pronation?

Mice which have a profile or design that allows, encourages or forces the hand to be physically higher at the index finger than on the little finger will result in a posture which is less pronated.  Typically these designs almost always provide a specific location for the thumb which allows it to comfortably rest at an almost vertical posture when compared to the other fingers.  Orthopedic Mice always include a less pronated posture to provide proper support and be orthopedically neutral.

What Other Equipment can be used to Reduce Pronation?

A simple 'do-it-yourself' solution is to create a mousing surface which is inclined to the outside of the body to reduce pronation in the mousing hand.  Some Mousing Surfaces incorporate this into their design.  However, changing the mouse itself is a more effective solution, and there is no way to reduce pronation when keyboarding if one is using a conventional keyboard, unless the individual is willing to saw their keyboard in half and re-solder all the connections to make it functional again.

 

Last edited December 16th, 2013

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