Why the Handshake Position is NOT Neutral

handshake is not neutral

handshake is not neutralThe so called “handshake” position of a vertical mouse has been discussed by many ergonomists.
Some claim that the handshake is a “neutral position” but research has shown that this is not the case at all.

In general a neutral posture refers to a relaxed position, so minimal tension of tendons, ligaments and muscles.
With respect to certain positions of the forearm though, there is a misunderstanding.

Handshake: Interosseous Membrane is Taut

It is generally assumed that the handshake position is neutral.
However, the forearm bone, called radius, is arched with respect to the other bone, the ulna. These two bones are connected by the interosseous membrane.

When one rotates the forearm into the handshake position, the distance between radius and ulna increases to a point where the membrane is taut.
Finger and thumb muscles which we use to lightly grip and hold an object are connected to this membrane.

One must therefore realize that gripping an object in the handshake position will actually introduce additional tension in the already taut membrane.
If we rotate the forearm to relax the membrane we will remove this harmful high tension.

Mouse Hand Must Be Supported at Angle of 25 Degrees

A hand supported at an angle of around 25 degrees with respect to a desktop realizes a truly neutral, tensionless membrane.
This prevents potential muscular and other damage during longstanding and repetitive movements.

Watch this short, one minute video:

An other interesting article addresses “Action is Reaction“;  Have a look there to understand the full picture.

Assessment of the Musculoskeletal Load of the Trapezius and Deltoid Muscles during Hand Activity

deltoid muscle

Stabilization of Hand Required for High Precision Tasks

During fundamental research and field research we noted the significance of a relaxed hand and forearm to operate a computer mouse. Gripping and pinching as well as reaching for the mouse showed to have severe negative effects on the upper extremity.

We require our hands to perform a great number of varying tasks with the mouse which requires high precision. Although Professor Van Zwieten, Department of Anatomy, BioMed, University of Hasselt mentions the possible risk of moving from the wrist in his paper “Hand Positions in scrolling, as related to PC-workers’ dystonia and treatment of dystonia by means of vibrostimulation and external shock waves therapy” (2009) we sometimes have to.

Danuta Roman-Liu, et al.

Higher precision requires stabilization of hand and forearm to minimize stress. It is from this perspective that we are pleased to be able to refer to the paper by Danuta Roman-Liu, et al. Department of Ergonomics, Central Institute for Labour Protection, Warsaw, Poland.

“Assessment of the musculoskeletal load of the trapezius and deltoid muscles during hand activity.” (2001). In this publication the following is mentioned:

First, higher precision of a task in which only the hand is involved, requires accuracy of movements which means more stabilization of the upper extremity and thus higher muscle tension. Furthermore, in view of the difficulty and possibly the complexity of the task a higher muscular tension can be expected.

No Effect on the Deltoid Muscle

Where is the Deltoid muscle?

The resulting muscle loads due to the performed task influences the tension of the trapezius muscle. Contrary to what is generally thought the study proves that there is no effect on the deltoid muscle.

It should be noted that the lower the level of force used, the more precise a difficult task can be executed. As a consequence, when the forearm is not supported, a higher tension of the descending part of the trapezius muscle results. We herewith refer to the paper by Professor Han Ming Chen of National Taiwan University “The effect on forearm and shoulder muscle activity in using different slanted computer mice” (2007) and our team of Erasmus University Medical Centre “Result of the use of a hand supporting computer mouse by patients with neck and shoulder complaints” (2006).

Support the forearm

So this publication proves the need to support the forearm when working with a computer mouse.

Hand Support when using a computer mouse

 

Recent Harvard Study Confirms HandShoe Mouse Principles

During our field study to develop the HandShoe Mouse, we noticed that a non supported arm resulted in complaints in neck and shoulders (Trapezius muscle). The advice to support the arm and let the hand rest on the body of the HandShoe Mouse quickly resulted in a reduction of complaints.
Our team of Erasmus University Medical Centre reported the field study in the paper “Result of the use of a hand supporting computer mouse by patients with neck and shoulder complaints” (2006).
These results are confirmed in the paper by Prof. Han Ming Chen “The effect on forearm and shoulder muscle activity in using different slanted computer mice” (2007).

Through the years we have been addressing the negative effects of the use of for example keyboard trays. This in view of the excessive muscle loads incurred due to forearm and hand not being supported.

Effects of Forearm and Palm Support

Therefore we are pleased that the recent study by the Harvard School of Public Health “Effects of forearm and palm supports on the upper extremity during computer mouse use” (2013) confirms these earlier studies.

In line with the above,Arm op Bureau 1-met vink web it is interesting to know that the use of a slanted mouse like the HandShoe Mouse prevents the possible negative effect of support of a forearm on a hard surface like a desktop. Of course a good alternative to provide the necessary support are chairs with armrests.

Desktops with sufficient space provide the significant advantage that one is free to move.

This contrary to arrangements which inhibit free movement and force a person in a rigid position without enough space to work e.g. put down papers etc.

In line with the above mentioned publications forearm and hand support are a prerequisite for a comfortable working position and to prevent unnecessary loads in Trapezius and deep neck muscles.