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Tool design, user characteristics and performance: a case study on plate-shears.
A Kilbom1, M Mäkäräinen, L Sperling
1Division of Applied Work Physiology, National Institute of Occupational Health, S-17184 Solna, Sweden.
Applied Ergonomics
|June 1, 1993
Summary
Male and female subjects showed differences in grip force and cutting performance with plate-shears. Modified shears improved male productivity, while reduced grip force in females indicated better tool adaptation.
Area of Science:
- Ergonomics and Human Factors
- Biomechanics
- Occupational Health
Background:
- Plate-shear cutting involves significant grip force and can lead to fatigue.
- Understanding gender-based differences in performance and tool design is crucial for optimizing work efficiency and safety.
Purpose of the Study:
- To investigate performance, grip forces, and fatigue during plate-shear cutting in male and female subjects.
- To evaluate the impact of modified plate-shears (spring grip, reduced grip span) on cutting performance and user preference.
- To identify factors influencing productivity, such as hand size and relative grip force.
Main Methods:
- Six male and six female subjects performed cutting tasks using standard and two modified types of plate-shears on three difficulty levels of plate material.
- Grip forces, cutting distance, cutting rate, and subjective exertion were measured.
- Electromyography (EMG) was used to assess muscle fatigue (frequency shifts).
- Multiple regression analysis was employed to determine the relationship between hand size, relative grip force, and productivity.
Main Results:
- Male subjects used lower relative grip force (approx. 40%) and achieved greater cutting distance than females (approx. 60% grip force).
- Despite similar fatigue indicators, females had a 50% lower cutting rate, likely explaining the lack of pronounced fatigue.
- Productivity was strongly correlated with hand size and relative grip force (R²=0.77).
- Modified plate-shears were preferred and increased male productivity by ~30%, but not female productivity.
- Modified shears with a spring grip and reduced grip span allowed females to decrease relative grip force from ~65% to 50%.
Conclusions:
- Hand size and relative grip force are key determinants of plate-shear cutting productivity.
- Modified plate-shears can enhance performance, particularly for males, by optimizing grip mechanics.
- Ergonomic tool design, considering factors like grip span and spring assistance, can improve efficiency and reduce exertion, especially for individuals with smaller hand sizes or different force application strategies.