Estimating dynamic external hand forces during manual materials handling based on ground reaction forces and body...

Area of Science:

• Biomechanics
• Ergonomics
• Occupational Health

Background:

• Direct measurement of hand forces is often impractical in manual materials handling (MMH) assessments.
• Existing methods may not be suitable for field or specific laboratory settings like patient handling.

Purpose of the Study:

• To propose and evaluate a novel method for estimating hand forces during MMH tasks.
• To assess the accuracy of this estimation method using ground reaction forces (GRFs) and body segment accelerations.

Main Methods:

• Ten male subjects performed a manual lifting/carrying task.
• 3D full body kinematics were captured using an optoelectronic motion tracking system.
• 3D GRFs were measured using a force plate, and 3D hand forces were measured using an instrumented box.

Main Results:

• The proposed method estimated 3D hand forces by subtracting body segment weight and acceleration forces from measured GRFs.
• Root-mean-square differences (RMSD) between estimated and measured hand forces ranged from 11 to 27N.
• Ignoring segment accelerations resulted in significantly higher errors (RMSD: 21–101N).

Conclusions:

• The novel hand force estimation method based on GRFs and body accelerations demonstrates good performance.
• Accounting for body segment accelerations is crucial for accurate hand force estimation in MMH.
• Further validation with ambulatory field measurement systems is recommended.