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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 forearm and as a corollary the hand to a fully "palm down" orientation.  When the hands and forearms of an individual are flat on a desk, such as when working on a conventional "flat" keyboard or "flat" mouse, they have fully "pronated" their hands and forearms. 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). Due to physiology, past injuries, or developed conditions each individual will have their own unique range of comfortable postures.

Why is Excessive Pronation a Risk Factor?

When an individual forces their hands to pronate to maintain full contact with the input device, a Static Load and strain is placed on the joints, muscles, ligaments and membranes in the arm. That can lead to fatigue, discomfort, pain and eventually injury. Just as excessive pronation is something that individuals seeking to reduce the risk of injury should avoid, excessive Supination (over-rotating the hand past a vertical orientation towards a palms-up orientation) can be an equally significant risk factor.

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

As indicated earlier, each 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 for everyone, and there are multiple factors that need to be considered since 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 Fewer Drawbacks than Vertical Keyboarding). For mousing, there are not always tradeoffs in moving to a more vertical posture, which makes mice up to 30° a good option for almost all users, and mice up to 90
° an option worth considering 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 and Separated 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 provide a specific location for the thumb which allows it to rest comfortably while the fingers are at varying degrees up to a near vertical orientation. Orthopedic Mice and Vertical Mice always include a less pronated posture to provide proper support and be orthopaedically neutral.

What Other Equipment can be used to Reduce Pronation?

A simple "do-it-yourself" solution is to place your mouse pad on a binder with the rings on the binder closer to the midline of the body. This will create a mousing surface which is sloped with the thumb side of the hand higher than the pinky side of the hand. Some Mousing Surfaces incorporate this into their design.

Changing the mouse itself is a more effective solution since mice of this design also generally incorporate additional ergonomic improvements. As for the keyboard, 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 July 17th, 2018

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