Nihon Kikai Gakkai ronbunshu (Jun 2023)
Estimation of physical burden while holding a box in a half-crouching position using a whole-body finite element model with 3D skeletal muscles
Abstract
In the super-aged society, the social role of nursing care industries is increasing. Many workers in the industries have the low back pain. Countermeasures to prevent it in the field of nursing care are urgent issues. One of the causes of the low back pain is known as an increase in lumbar intervertebral pressure. However, it is very difficult to measure the lumbar intervertebral pressure in a non-invasive manner. The goal of this research is to develop a human body finite element (FE) model to estimate physical burden such as the low back pain. In this paper, we investigated the validity of model prediction such as muscle activity and intervertebral disc pressures in a half-crouching position, which is a common posture causing the low back pain. An experiment using a human adult male volunteer was conducted to compare with the prediction results. The participant kept a half-crouching position while holding a box with his both hands. Activity of 16 superficial muscles was measured in three conditions of 0.6 kg, 9.2 kg, and 18.0 kg as the weight of the box. Under three conditions similar to the experiment, the muscle activity and intervertebral disc pressures when holding a box in a half-crouching posture were calculated using the human body FE model. The trend of change in the calculated muscle activation levels for each box weight generally showed good agreement with the experimental data. Predicted results of intervertebral disc pressures from the third lumbar to the fifth lumbar spine vertebra generally agreed with test data obtained from the literature. Muscle activity and distributions of intradiscal pressures, muscle contractile forces, and tensile strains of muscle and tendon changed according to the weight of the box. These results demonstrated that this model has the possibility of evaluating physical burden when holding a box.
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