Ergonomic Mouse Evaluation

On this page you'll find a selection of the slides from a PowerPoint presentation based on the Research of Erasmus University and EMG measurements performed by Maastricht University.
We have added some notes in red.

The EMG measurements show the muscle activity depending on the mouse you are using.

For a download of the complete presentation: ergonomic mouse evaluations.

Evaluation of 8 ergonomic computer mice
a regular mouse and
the HandShoe Mouse by Hippus

Professor C.J. Snijders PhD, former head dept. of Biomedical Physics and Technology, Erasmus MC, University Medical Center Rotterdam

EMG measurements executed by the Medical Center of Maastricht University.

• extensor muscle load, hand & fingers hover above the mouse  
• Cinderella effect, exertion of unnecessary static forces  
• gripping and pinching  
• too large supination angle  
• excessive ulnar deviation of the wrist, "hand shake position"  
• excessive extension of the wrist  
• hand and lower arm hover above an object  

Note: The HandShoe mouse has been designed
to prevent all these types of physical load.

Physical load type I

With the existing computer mouse fingers have to remain
elevated in between switching to prevent inadvertent switching.
This results in extensor load.

EMG values show the level of muscle activity:

                               visible moments of rest                                             no moments of rest

Physical load type II

Cinderella effect, exertion of unnecessary static forces:

Objects that induce gripping and pinching due to shape:

• the regular mouse, too small for the average hand,
  held between thumb, ring finger and little finger 
• thin, pen like objects, held between thumb, ring finger and
  little finger 
• handle shape objects, gripped by the entire hand 

A too large supination angle: objects force hand and lower arm in a strained position:

                                      relaxed hand:
                               supination angle of around 15 deg.

Note: EMG measurements confirm that the vertical position
of the hand is causing unwanted muscle exertion.

“Hand shake position”, a too large supination angle combined with an excessive ulnar deviation:

The hand is forced in a position resulting in an ulnar deviation of the wrist outside the regular functional area.

Physical load type VI

A too large extension angle of the wrist:
Corresponding with load type V the hand and wrist are forced outside the functional area.

Physical load type VII 

Hover the hand and arm above an object:

For example the use of a pen in combination with a tablet forces hand and possibly forearm in a hovering position to allow for a free motion over the tablet. 

Evaluation of ergonomic computer mice 

A number of ergonomic computer mice were made available for the evaluation programme. The use of these mice resulted in complaints with the users. The source of these complaints could in general be attributed to the aforementioned 7 types of physical load factors.

Muscle exertion has been measured by means of EMG

Evaluation of ergonomic computer mice 

The Medical Center of Maastricht University, the Netherlands, has performed the necessary EMG measurements.

The protocol consisted of:
10 sec. rest,
10 sec. motion,
10 sec. rest
10 sec motion, however with the left button active.

Sources of physical load 

Regular mouse

In general the regular mouse is too small for the average hand resulting in a grip like action of thumb, ring finger and little finger
and thus excessive loads on metacarpal bones and ligaments.

• excessive extensor load 
• excessive thumb load 
• instigates working from the wrist 
• instigates gripping and pinching
  

EMG signal of a regular mouse 

1. extensor carpi radialis longus (red line)
2. extensor carpi radialis brevis (yellow line)

Note: there is no rest in the signal at all

Source of physical load 

Vertical mouse
Forces the hand in an almost vertical position. The hand rests on its side. This generates excessive friction between hand and table top while working.

Ref. publication prof. Han Min Chen “The effect on forearm and shoulder muscle activity in using different slanted computer mice”

• a too large supination angle 
• hand rests on its side 
• mouse is gripped between palm of the hand, fingers and thumb 
• this position instigates gripping and pinching 
• metacarpal bones and ligaments are stressed 
• excessive tension in muscles of the lower arm 

EMG signal of vertical mouse 

                        1. extensor carpi radialis longus (red line)
                        2. extensor carpi radialis brevis (yellow line)

Note: the vertical mouse has no rest in the signal at all, just like a standard mouse.
This, among others, is the result of the reaction force of the thumb with respect to the fingers when switching.

Source of physical load 

Joystick, mouse with handle

This mouse instigates gripping and pinching. As a result muscles are excessively strained and arm movement is restricted.

Ref. publications in Clinical Biomechanics by prof. Han Min Chen “The effect on forearm and shoulder muscle activity in using different slanted computer mice” and Gustafsson and Hagberg “computer mouse use in two different hand positions: exposure, comfort, exertion and productivity”

• a too large supination angle 
• hand is positioned on its side 
• one grips the handle 
• position instigates excessive gripping and pinching
  

EMG signal joystick, mouse with handle -1 

                       1. extensor carpi radialis longus (red line)
                       2. extensor carpi radialis brevis (yellow line)

EMG signal joystick, mouse with handle -2 

                               flexor carpi radialis (red line)

Minimal physical loads with the Hippus mouse

The Hippus (HandShoe) mouse
The shape is based on the hand in a relaxed position.
Fingers and thumb rest supported. A light contraction of flexor muscles suffices to switch. The scroll wheel is positioned close to the finger tips to allow for minimal movements.

• hand, wrist and thumb are fully supported 
• extensor muscles are relaxed 
• shape prevents gripping and pinching 
• scroll wheel positioned between index and middle finger 
• to stimulate arterial flow large movements are possible 

EMG signal of the HandShoe Mouse 

                  1. m. extensor carpi radialis longus (red line)
                  2. m. extensor carpi radialis brevis (yellow line)

Conclusion 

• mice investigated show on average high EMG values 
• EMG values of extensor muscles indicate high level of activity 
• a number of mice show continuous high flexor loads
  with a number of mice hand and/or arm are forced into positions which cause unnecessary stresses and strains 
• the design is based on the natural relaxed position of
  hand and arm 
• shape and weight realize a reduction of muscle load and thus EMG values 
• the Hippus mouse supports the hand continuously, during action as well as in rest 

Downloads 

You may download the full presentation by clicking on the link below:

 Evaluation of 8 Ergonomic Computer Mice (PDF 3,1 Mb) 

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