Wrist posture affects hand and forearm muscle stress during tapping

Area of Science:

• Biomechanics
• Occupational Health
• Ergonomics

Background:

• Non-neutral wrist postures are identified as a significant risk factor for musculoskeletal disorders in computer users.
• Understanding the internal biomechanical loads on hand and forearm muscles during computer use is essential for developing effective prevention strategies.

Purpose of the Study:

• To quantify and compare the internal muscle stresses in the hand and forearm during key tapping in various wrist postures.
• To investigate the relationship between different wrist postures and the resulting muscle loading patterns.

Main Methods:

• Ten healthy subjects performed key tapping tasks in four distinct wrist postures: straight (neutral), ulnar deviated, flexed, and extended.
• Joint torques were calculated from measured joint kinematics and fingertip forces.
• A musculoskeletal model and optimization algorithm were employed to estimate muscle stresses for six finger and four wrist muscles.

Main Results:

• Non-neutral wrist postures led to significantly higher muscle stresses compared to the neutral posture.
• Wrist extensor muscles consistently exhibited greater stress than flexor muscles across all tested postures.
• Sustained high motor unit recruitment in extensors, especially in flexed wrist postures, indicates an elevated risk of injury.

Conclusions:

• Maintaining a neutral wrist posture during keying activities is critical for reducing internal tissue loading and mitigating the risk of musculoskeletal disorders.
• The findings highlight the importance of ergonomic interventions promoting neutral wrist alignment for computer users.