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


Ergonomic Mouse – Stop Reaching

OPC Ergonomics distributor HandShoe Mouse

If you use an ergonomic mouse or not, this information will show you that you should stop reaching while using your ergonomic mouse to prevent shoulder pain.

Do your neck and shoulders ever feel stiff, after a days work behind your PC or laptop?

This is mainly caused by the large muscles, which run along the upper part of your back up to the base of your skull, the so called trapezius or trap muscles. You can feel them when stretching one arm forward and touching the area between your neck and shoulder with your other hand.
Then you will clearly feel that reaching for mouse and keyboard forces these muscles to be unnecessarily active.

Various studies show the importance of a relaxed posture which also means not to reach when using your mouse.
Some people believe that providing support at the wrist is sufficient, but you can feel yourself that this doesn’t reduce the strain on the neck -shoulder area.
Electro myogram measurements have proven the positive effect of supporting your arm.

The handshoe mouse provides support for hand and fingers to allow the forearm to relax.
Make sure you also support your forearm on your desktop or arm rest, which prevents reaching.
Now your neck and shoulders will feel relaxed, even after a hard days work!

Ergonomic Mouse Video – Stop Reaching

The short ergonomic mouse video below shows why you should stop reaching when using an ergonomic mouse.