Smaller external notebook mice have different effects on posture and muscle activity

Area of Science:

• Ergonomics
• Biomechanics
• Occupational Health

Background:

• Extensive computer mouse use is a risk factor for work-related musculoskeletal disorders.
• Notebook computer mouse designs vary in size but their impact on biomechanical risk factors is not well-understood.

Purpose of the Study:

• To evaluate the biomechanical effects of different notebook computer mouse sizes.
• To assess the influence of mouse size on posture and muscle activity during computer tasks.

Main Methods:

• Thirty adults performed standardized mouse tasks using five notebook mice of varying dimensions and one desktop mouse.
• Motion analysis captured index finger, wrist, and forearm postures.
• Electromyography measured muscle activity in forearm extensor muscles and the first dorsal interosseus.

Main Results:

• The smallest notebook mice resulted in less neutral postures (e.g., increased metacarpophalangeal joint adduction/flexion, wrist extension) and higher wrist extensor muscle activity.
• Participants with smaller hands exhibited more non-neutral postures overall, while larger-handed participants were more affected by smaller mice.
• Larger mice were preferred for comfort and usability, despite smaller mice being favored for portability.

Conclusions:

• The smallest notebook mice intensify biomechanical exposures, potentially increasing the risk of work-related musculoskeletal disorders.
• Prolonged use of smaller notebook mice may exacerbate these biomechanical differences over time.
• Mouse design, particularly size, is a critical factor in the prevention of computer-related musculoskeletal issues.