Research Shows Why You Should Use A HandShoe Mouse
Repetitive Strain Injury (RSI) and certain types of Carpal Tunnel Syndrome (CTS). These types of complaints instigated fundamental and field research with several medical universities in Europe.
At Erasmus University Medical Center in the Netherlands fundamental research showed that a source of these complaints can be found with the computer mouse. For example gripping and pinching and hovering of the fingers above the buttons proved to be a major source.
Gripping and pinching has a significant negative effect on the deep neck muscles. To prevent this tension, the so called kinetic chain from fingers to deep neck muscles must be relaxed. To realise relaxation, support of hand and forearm is required to reduce loads on shoulders and arms.
The following images show both Trapezius and Deltoid muscles which are unnecessarily loaded when hand and arm are not supported.
Negative effect of gripping and pinching as well as hovering
The effect on the deep neck muscles due to gripping and pinching as shown during fundamental research is explained as follows.
The major artery as well as nerves (Brachial plexus) run into our arm via the Costoclavicular gate (Thoracic outlet). This gate between first rib and collar bone narrows due to tense deep neck muscles. Contraction of these muscles pulls the first rib against the collar bone. This tension may therefore cause obstruction of flow in arteries and veins and possibly pinch nerves.
A tingling feeling in fingers, numbness and cold hands may result.
All these symptoms are indications of RSI and can cause certain types CTS.
Why the HandShoe Mouse provides the required muscle relaxation
The following images show EMG signals and thus the effect on muscle tension when using a regular mouse and the first prototype of the HandShoe Mouse. The latter fully supports the hand, fingers and thumb in a relaxed fashion. This results in removing continuous muscle tension as is visible ( continuous EMG signal) with a regular mouse due to gripping and pinching, as well as hovering of the fingers and palm above the mouse body.
One must therefore conclude that a supported hand and fingers provide the necessary relaxation in the kinetic chain from the fingers to the deep neck muscles, which can now relax.
Based on fundamental research it may be assumed that musculoskeletal disorders (MSD) can be prevented by the introduction of a hand supporting (ball shape) body as this results in minimal (intermittent) EMG values and thus lower Minimal Voluntary Contraction (MVC). Research has shown that a reduction of MVC to below 4 % prevents irritation of muscles and tendons.
A major Dutch insurance company approached the research team during its field research, with the request to evaluate results by comparison with already available regular and so called ergonomic computer mice. The results of this evaluation are presented and can be downloaded here.
What is the neutral hand position?
Contrary to what is generally defined as neutral, it is proven that the so called handshake position is not neutral.
Fundamental anatomical research at the Medical Center of Hasselt University in Belgium, has shown that the (interosseous) membrane between forearm bones (ulna and Radius), is taut or lax, depending on hand and forearm positions.
This explains the possible muscle irritation when, for example, a vertical m0use is used.
The thumb and index finger long muscles, which are necessary to operate and grip a mouse, originate from the Interosseous Membrane.
The following image of these muscles show their position.
In the hand shake position, the grip force to hold the mouse is transferred to the already taut Interosseous Membrane.
This may result in irritation and probably in due course physical complaints.
Studies of the anatomy prove that using a lightly slanted computer mouse requires least muscle activities:
By rotating the forearm and hand to around 250 to 300 (“supination”) as with the HandShoe Mouse, the Ulna and Radius, will partly follow each other’s curvatures, which leaves the Interosseous Membrane lax and undulated.
In such a position maximal relaxation is realized.
The following images show a vertical mouse and resulting taut IOM, forearm bones Ulna and Radius in plane.
Note: transition from a regular mouse to a so called vertical one, initially looked like a good solution. Over-strained muscles got a chance to relax which was experienced as a relief.
However, experience in the field shows that contrary to what was expected, over time irritation in the forearm started to re-occur. The generally assumed so called “neutral handshake position” is proven not to alleviate grip forces.
Forces in fingers and thumb due to gripping and pinching
When a regular mouse or a vertical mouse is used, excessive stresses and strains in fingers and thumb result, as a consequence of gripping and pinching when holding the mouse.
Not only the size of a mouse is significant, but as already shown, also its shape can be a source of complaints.
Regular and vertical mice force the hand into a cramped position, in order to operate the switches. ( See images below).
In general, when gripping the mouse, fingers instigate forces and the thumb acts as a reaction force.
With a regular mouse torque forces in the finger joints also occur (Proximal)
Next to these forces in the fingers we should be aware of the reaction force in the major thumb joint (CarpoMetaCarpal, CMC). It is obvious that the CMC joint may suffer from wear and tear due to intense use and heavy loads instigated by the fingers in the thumb (grip force).
Risk of complaints due to gripping and pinching
In view of the intensity with which we use the computer mouse for our daily tasks, we must realize that in time we run an increased risk of joint erosion due to gripping and pinching.
As developer and producer of the HandShoe Mouse, Hippus regularly gets information from the field with respect to these complaints (CMC and PIP). Recent studies at the Medical Center of Hasselt University have concentrated on this subject. We therefore draw the attention to the fact that working with a regular or so called ergonomic mouse may increase the risk of joint erosion and thus degenerative arthritis.
One should be aware that the induced tensions in the joints can even lead to inflammation, rheumatoid arthritis.
Although complaints like arthritis cannot be cured by the HandShoe Mouse, it can reduce this risk significantly.
The risk of De Quervain’s Syndrome, another complaint in the thumb is also reduced by using the HandShoe Mouse.
The effect of the supported arch of the HandShoe Mouse
Contrary to a regular or vertical mouse the contour of the HandShoe Mouse body provides full support for hand palm, fingers and thumb. Fingers can relax instead of being forced to continuously hover over the switches.
The supporting arch relieves stresses and strains in the finger joints (PIP).
A similar supported position is provided for the thumb to protect its major joint (CMC).
This design allows the user to move the HandShoe Mouse and thus cursor without gripping or pinching the mouse body. Furthermore, only a minor contraction of the fingers is required to switch.
This combination of full support and minor muscle action to operate the mouse provides prolonged relaxation which is not realized by computer mice of an alternative design.
HandShoe Mouse prevents skin irritation
With the increased use of computer mice skin irritation of the hand is noticed more frequently. Recent research resulted in papers where skin irritation due to friction over the desktop from prolonged use of a computer mouse is reported. Thickening of the skin (mousing callus) is one of the results.
The repetitive friction, pressure, and shear between the hand palm and desktop apparently even led to the development of eczema.
The following images show the described skin irritation and the source.
The hand palm supporting concept of the HandShoe Mouse prevents skin contact with the underlying surface and thus the above presented skin irritation.
Prevent excessive wrist loads (wrist snap)
Freedom of movement of arm and hand on the desktop is essential.
Contrary to the general accepted practice with respect to regular mice and the so called ergonomic mice one should not use a wrist support because this will only restrict movement.
When movement is restricted one has to move the mouse from the wrist.
Excessive wrist movements (wrist snap) can cause detrimental loads on the wrist joint while forearm muscles need to be highly active for this type of movement. Working from the wrist should therefore be restricted.
To prevent excessive wrist loads forearm and hand need to be supported in the correct fashion (supination at around 25 to 30 degrees).
The following images show how best to work with the HandShoe Mouse and reduce the risk of wrist pain. To move the cursor on the screen you only need to move within the indicated green triangles for arm and hand.
The above information is based on fundamental and field research. It is substantiated by various peer reviewed papers and presentations, see the HandShoe Mouse Publications Page.
The so called neutral or “handshake” position results in a maximally taut membrane between Ulna and Radius. In general thumb and index finger long muscles originate from this forearm interosseous membrane. Therefore the need to grip and pinch a vertical mouse results in unnecessary strains in the already taut membrane and may cause physical complaints. (for publication click here)
Watch this one minute video on the right, showing that the “handshake position” is NOT neutral and how to use your forearm when using your mouse.
Studies with regard to the design of the PC-mouse by National Taiwan University (for publication click here) and Erasmus University Medical Center have resulted in a slightly slanted mouse body as with the HandShoe Mouse to prevent these physical complaints.