Effects of loading processes on contact forces when simulating static seating with a finite element human body model

Area of Science:

• Biomechanics
• Human Body Modeling

Background:

• Seat interface forces, especially shear forces, are critical for predicting pressure ulcers and seating discomfort.
• Current static seating simulations using finite element human body models (HBMs) often employ a gravity drop (DROP) method, which inaccurately represents the natural sitting process.
• High coefficients of friction (COF) are frequently used in simulations, potentially leading to unrealistic tangential forces.

Purpose of the Study:

• To investigate the impact of different loading processes and COF on seating simulations using HBMs.
• To introduce and evaluate a novel 'drop and rotate' (D&R) loading method designed to more accurately simulate how individuals sit.
• To compare the D&R method against the conventional DROP method in terms of force prediction and sensitivity to COF.

Main Methods:

• Development and application of a 'drop and rotate' (D&R) loading technique for HBM static seating simulations.
• The D&R method involves initial trunk flexion followed by hip rotation to establish contact, mimicking natural sitting.
• Simulations were conducted on a validated adult male HBM across two distinct seat configurations.

Main Results:

• The D&R method demonstrated reduced sensitivity to COF compared to the DROP method.
• The D&R approach yielded more accurate predictions of contact forces, particularly on the seat pan.
• While more computationally intensive, the D&R method offers improved simulation fidelity.

Conclusions:

• The loading process significantly influences the outcomes of static seating simulations.
• The proposed D&R method provides a more realistic simulation of seating biomechanics and improves the prediction of interface forces.
• Future research should consider the D&R method for more accurate HBM seating analyses to mitigate risks like pressure ulcers.