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Risk Factors and Sources of Injury > Static Grip Force When Using the Mouse          
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Hand Gripping MouseStatic Grip Force When Using the Mouse

What is Static Grip Force?

Static Grip Force refers to the requirement imposed by conventional mice on the individual to maintain a constant pinch force or grip force on the mouse in order to control and direct the mouse and perform mousing operations.  This arises due to the symmetrical design of traditional mice and also the reality that they are usually not Orthopedic Mice which are sculpted or sized to support the bone structures and muscle systems of the hand.  By failing to take into account the anatomy of the hand, individuals are forced to maintain a steady pinch grip force on the sides of the mouse in order to be able to accurately move the mouse and achieve precise cursor movement.  This distorts the normal neutral, relaxed hand posture to an awkward one which affords sufficient control of the mouse.  Due to common poor behaviors, individuals will maintain this grip and exertion even when not actively targeting or using the mouse, resulting in far more strain and fatigue than one would otherwise expect to arise from a high effort task.

Why is Static Grip Force a Risk Factor?

When an individual is required to force their hands to maintain full control of the mouse, this puts a static load and strain on the joints, muscles and membranes in the hand, wrist and arm which can lead to fatigue, discomfort, pain and injury. 

In extreme cases this can lead to a 'death grip' on the mouse, i.e. the situation where the static grip behaviour has become so entrenched that the user is now maintaining an excessive grip on the mouse out of habit. This will also often lead to a user's involuntary gripping or pinching of the fingers, even when not using a mouse or pointing device. Clearly, Static Grip Force is a risk factor with pointing devices that needs to be reduced or eliminated entirely for users to prevent the risk of injury over the long term.

How Much Static Grip Force (or Pinch Force) is 'OK' and not a Risk Factor?

Every individual has different degrees of strength, dexterity, endurance and fatigue rates in the muscles in their hands.  For most individuals, anything other than a minimal amount of pinch or grip force can cause fatigue and pain in the muscles if the action is continually performed over an extended period of time (e.g. gripping the mouse even while not actively using the mouse through the workday).  If an individual uses their mouse for only brief periods without intensity, this temporary non-neutral posture and muscle exertion may not cause any long-term hand condition.  However, as noted earlier, the failure to remove the hand from the mouse significantly extends the period.  Any user who intensively uses the mouse for even an hour a day, or users who regularly perform mousing activities throughout the day should be aware of this risk factor.

Top View of Hand with Tendons ExposedWhat are the Symptoms of 'Too Much' Static Grip Force?

When a user has to use 'too much' Static Grip Force, the flexor muscles of the hand (that one uses to make a 'fist') will be overused and create a strength unbalance (relative to the use of the extensor muscles which are used to open the hand).  Typically the pain will be throughout the hand and wrist and radiate up the forearm.  The localizations are most commonly in the underside of the hand under the thumb (thenar eminence), the top or back of the hand (transverse carpal ligament) or the underside of the forearm either at the wrist (flexor retinaculum) or about 2-4" up from the wrist (flexor carpi radialis).  Typically the pain is a burning constant pain, without pulses or significant variance.

What is 'Death Grip'?

A subsequent more serious condition which can arise from Static Grip Force is 'Death Grip'.  This refers to the situation where many users continue to maintain a viselike grip on their mouse even during periods of inactivity to the point where the user's hands never get a chance to rest. Exacerbating this is the reality that most users tend to grip the mouse harder than is required in order to increase the feeling of control while working, enough to 'kill' a regular living mouse, thus the term 'Death Grip'.

How can the Choice of Mouse Help to Reduce Static Grip Force?

Orthopedic Mice are orthopedically sized and sculpted and can reduce or eliminate the need and even the possibility of static grip force while using a mouse by relying upon gravity and the profile to provide control without a requirement of grip force.  Other types of pointing devices such as Central Pointing Devices, Touchpads, and Trackballs take away the source of grip force, by using a different paradigm for mousing and removing the cause (grasping an object) from the action of mousing.

What Other Strategies can be used to Reduce Static Grip Force?

A simple do-it-yourself solution is to take the hand off the mouse when not actively mousing, which greatly reduces the amount of time spent gripping the mouse.  This will ensure that the hand is only grasping a non-ergonomic mouse when actively mousing. 


Last edited December 16th, 2013

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