Smaller external notebook mice have different effects on posture and muscle activity.
BACKGROUND
Extensive computer mouse use is an identified risk factor for computer work-related musculoskeletal disorders; however, notebook computer mouse designs of varying sizes have not been formally evaluated but may affect biomechanical risk factors.


METHODS
Thirty adults performed a set of mouse tasks with five notebook mice, ranging in length from 75 to 105 mm and in width from 35 to 65 mm, and a reference desktop mouse. An electro-magnetic motion analysis system measured index finger (metacarpophalangeal joint), wrist and forearm postures, and surface electromyography measured muscle activity of three extensor muscles in the forearm and the first dorsal interosseus.


RESULTS
The smallest notebook mice were found to promote less neutral postures (up to 3.2 degrees higher metacarpophalangeal joint adduction; 6.5 degrees higher metacarpophalangeal joint flexion, 2.3 degrees higher wrist extension) and higher muscle activity (up to 4.1% of maximum voluntary contraction higher wrist extensor muscle activity). Participants with smaller hands had overall more non-neutral postures than participants with larger hands (up to 5.6 degrees higher wrist extension and 5.9 degrees higher pronation); while participants with larger hands were more influenced by the smallest notebook mice (up to 3.6 degrees higher wrist extension and 5.5% of maximum voluntary contraction higher wrist extensor values). Self-reported ratings showed that while participants preferred smaller mice for portability; larger mice scored higher on comfort and usability.


CONCLUSIONS
The smallest notebook mice increased the intensity of biomechanical exposures. Longer term mouse use could enhance these differences, having a potential impact on the prevention of work-related musculoskeletal disorders.
Oude Hengel
Karen M
KM
Faculty of Human Movement Science, VU University Amsterdam, Van der Boechorststraat 9, 1081 BT Amsterdam, The Netherlands.
Houwink
Annemieke
A
Odell
Dan
D
van Dieën
Jaap H
JH
Dennerlein
Jack T
JT
D000222:Adaptation, Physiological; D000328:Adult; D001132:Arm / Q000502:physiology*; D016287:Computer Peripherals; D005260:Female; D006225:Hand / Q000502:physiology*; D006801:Humans; D008297:Male; D008838:Microcomputers; D009043:Motor Activity / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D013647:Task Performance and Analysis