Short-term changes in upper extremity dynamic mechanical response parameters following power hand tool use

Area of Science:

• Occupational Health
• Biomechanics
• Ergonomics

Background:

• Power tool operation can impact upper limb physiological and mechanical properties.
• Understanding these effects is crucial for preventing work-related musculoskeletal disorders.

Purpose of the Study:

• To investigate the effects of power tool usage on upper limb mechanical response and physiological properties.
• To determine how tool factors like peak torque and torque build-up time influence these effects.

Main Methods:

• Twenty-nine inexperienced users operated a pistol grip nutrunner under controlled conditions (peak torque, build-up time).
• Measurements included dynamic mechanical response (stiffness, damping, effective mass), physiological properties (strength, swelling), and upper limb symptoms.
• A biomechanical model estimated handle force and displacement.

Main Results:

• Isometric strength decreased immediately post-use (15%) and at 24 hours (9%).
• Mechanical stiffness and effective mass were significantly affected by torque build-up time (p < 0.05).
• Longer build-up times (250 ms) resulted in greater decreases in stiffness (43%) and effective mass (57%) and increased discomfort.

Conclusions:

• Power tool operation, particularly with longer torque build-up, negatively impacts upper limb mechanical properties and strength.
• Higher predicted handle forces and displacements correlate with reduced stiffness, reduced effective mass, and increased discomfort.
• Findings highlight the importance of tool design and usage parameters in mitigating occupational risks.