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Effect of different self-selected walking speeds in leveling of body center of mass, mechanical work and energy in healthy children

Carriquiry Mariana, Silva-Pereya Valentina, Jerez-Mayorga Daniel, Fabrica Gabriel

Acta of Bioengineering and Biomechanics

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2021

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Vol. 23, no. 3

125--131

EN

Purpose: The aim of the study was to analyze the general kinematics of the cycle, leveling of the center of mass and inverted pendulum model in school-age children when they walk at three different auto-selected speeds. Methods: The kinematics of walking cycle, angular actions that contribute to reducing the vertical displacement of body center of mass (pelvis, hip, knee and ankle) and pendulumlike determining variables (mechanical work, pendulum-like recovery and congruity percentage), were analyzed in children for three different self-selected speeds. Differences for each variable with the speed were tested by ANOVA with Bonferroni post-hoc analysis. Omega squared (ω2) was calculated for the values of the effect sizes. Results: None of the angular variables associated with the leveling of the vertical trajectory of body center of mass changed. Likewise, recovery and congruity percentage presented values similar to those obtained in previous studies and did not show significant changes with the speeds. Conclusions: Nevertheless, changes in horizontal mechanical work and cycle phases, indicate that at some point during the cycle the mechanical energy transfer may have been affected for speed changes. Our results warn about the implication that small changes in the speed during functional evaluations of gait in children may have.

2

The approach to mining safety improvement: Accident analysis of an underground machine operator

Karliński J., Ptak M., Działak P., Rusiński E.

Archives of Civil and Mechanical Engineering

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2016

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Vol. 16, no. 3

503--512

EN

This paper presents the numerical approach to the safety and ergonomics issues regarding the biomechanics of the mining machine operator. Based on actual accidents, the authors analyzed the current requirements for protective structures in regard to operator safety aspects. The study found that the current type-approval tests do not examine phenomena related to typical accidents in underground mines, such as rock bursts resulting in thill uplift, lateral rock tosses, or cover caving. In many cases it may result in severe or fatal injuries of the mining machine operators. Thus, the authors incorporate a precise human model into operator safety tests and conducted numerical simulations by the use of the coupled Finite Element and MulitBody codes. To mitigate the injuries, the state-of-the-art seat absorber was implemented underneath a typical operator's seat. The device was designed to dissipate the kinetic energy during the process of rapid floor uplift and immediate velocity change from the cab to gallery roof impact. In order to compare the energy-dissipating capabilities of the absorber two approaches were selected for the same boundary conditions: a standard seat and seat with absorber mounted in the cab during the impact. The cab initial velocity was the main variable during the simulations. Finally, the injury criteria for the standard seat and the new approach with the energy-absorbing device were collated and contrasted.

3

The fundamentals of biomechanical modelling in transport facilities

Więckowski D.

Archiwum Motoryzacji

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2011

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Nr 2

81-96

EN

The fundamentals related to biomechanical modelling have been discussed in this paper from the engineer.s point of view. The paper is a kind of review and it is to present various biomechanical modelling methods used to study the phenomena taking place in transport facilities. Reference has been made to the history of development of the modelling, with directing particular attention to the beginnings of the modelling. Definitions of the term "model" have been quoted and various model types have been discussed. The idea of "biomechanics" has been defined. The method of building a model of the human body has been shown. Attention has been drawn to the major segments of the human body from the point of view of taking the segments into account in the modelling process. The difficulties challenging the modelling of body movements and forces acting on the body have been described. The classification of biomechanical models has been presented, with the characteristic features and examples of application of such models having been described: Various types of biodynamic models, including physical, mathematical, and animal models, have been pointed out. Differences in the modelling of a human body depending on the model adopted have been highlighted. A number of modelling examples have been presented. In the conclusions, it has been emphasised that a specific biomechanical model may represent only a few aspects of the human body. On the other hand, model validation should include comparisons between the predictions of the model and independent observations of the predicted responses. Directions of further work on the modification and development of models have been recommended.

PL

W pracy omówiono podstawy związane z modelowaniem biomechanicznym w ujęciu inżynierskim. Praca ma charakter przeglądowy, a jej celem jest przedstawienie różnych metod modelowania biomechanicznego wykorzystywanych w środkach transportu. Nawiązano do historii rozwoju modelowania, zwracając uwagę na początki modelowania. Przytoczono definicję modelu oraz omówiono postacie modeli. Zdefiniowano pojęcie biomechaniki. Zaprezentowano sposób budowy modelu człowieka. Zwrócono uwagę na główne segmenty ciała człowieka w aspekcie uwzględnienia ich w procesie modelowania. Opisano trudności związane z modelowaniem ruchów ciała i działających na to ciało sił. Zaprezentowano podział modeli biomechanicznych oraz opisano charakterystyczne cechy i przykłady zastosowań. Zwrócono uwagę na różne rodzaje modeli biodynamicznych, w tym modele fizyczne, matematyczne i zwierzęce. Podkreślono różnice w modelowaniu człowieka w zależności od przyjętego modelu. Pokazano przykłady modelowania. W podsumowaniu podkreślono, że dany model biomechaniczny może odwzorowywać tylko kilka aspektów ciała ludzkiego. Natomiast badanie poprawności modelu powinno obejmować porównania pomiędzy danymi prognozowanymi przy użyciu tego modelu, a niezależnymi obserwacjami prognozowanych odpowiedzi. Wskazano kierunki dalszych prac związanych z modyfikacją, rozwojem modeli.

4

Biomechaniczny model układu człowiek - techniczne środki transportu

Nader M., Korzeb J.

Vibrations in Physical Systems

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2000

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Vol. 19

223--224