Biomechanical evaluation of lumbar articulators for load redistribution in occupationally exposed personnel with personal protective equipment

Abstract

Introduction
The lumbar region of the spine plays a fundamental role in load distribution and postural stability, particularly in occupationally exposed individuals such as armed forces personnel and their personal protective equipment (PPE). Prolonged use of PPE can create load concentrations in the shoulders, increasing the risk of fatigue and physical overexertion. This research evaluates the impact of using lumbar articulators as ergonomic devices to redistribute these loads and improve physical performance during operational activities.

Objective
To evaluate two lumbar articulator designs in order to analyze their capacity to redistribute loads in the spine and reduce stress concentrations in the shoulders of personnel occupationally exposed to the use of PPE. Secondary objectives include determining the ergonomic impact of the articulator on physical exertion and its effect on aerobic performance during prolonged activities. Methodology
An anthropometric study was conducted according to the protocols of the International Society for the Advancement of Kinanthropometry (ISAK) to characterize the target personnel. Subsequently, computer-aided engineering (CAD/CAM) tools were applied to analyze mechanical stresses, developing free-body diagrams and structural simulations using the finite element method (FEM). Two lumbar articulator prototypes were evaluated, comparing their performance under loads associated with the use of personal protective equipment (PPE).

Results
The analyses showed that Lumbar Articulator 1 withstood the simulated loads without exceeding the yield strength of the ABS material, maintaining the structural integrity of all its components. In contrast, Lumbar Articulator 2 exhibited critical failures in the outer vertebra and at the joint during extension simulations. These results demonstrate significant differences in load capacity and structural efficiency between the two designs. Conclusions
Redesign of the Lumbar Articulator 2 is recommended, particularly in areas of stress concentration, by modifying its geometry and radii of curvature. Furthermore, dynamic analyses are suggested to evaluate alternating stresses during lumbar flexion and extension. In ergonomic terms, the use of lumbar articulators presents significant potential for reducing physical fatigue, improving load distribution, and increasing the efficiency of personnel exposed to the use of PPE.