Multi-scale Modeling And Simulation Of Skeletal Muscles Based On Micro And Macro Characteristics Of Half-sarcomeres

The human musculoskeletal system is a nearly perfect biomechanical system evolved over millions of years in nature.The skeletal muscle in the musculoskeletal system can reasonably withstand external and internal loads and effectively control the movement of various parts of the body.In the past century,human beings have never stopped exploring the mystery of skeletal muscle mechanics.The related mechanism of skeletal muscle spans multiple scales from micro to macro,and is modeled by multi-scale method.On the micro scale,the working mechanism of the smallest motor unit in skeletal muscle fiber can be explored.On the macro scale,the relationship between the muscle contraction length and muscle strength presented by the whole muscle can be discussed.Establishing a multi-scale model of skeletal muscle is of great significance for clarifying the mechanism of skeletal muscle strength and exploring the relationship between muscle morphological changes and muscle strength changes.Skeletal muscle contraction is sometimes accompanied by non-uniformities of half-sarcomeres,which is considered to be one of the important causes of muscle fatigue.First of all,in this paper,we reproduced and reviewed the modeling ideas of the traditional skeletal muscle model.The traditional model starts from two aspects of phenomenology and mechanism,and try to explain the mechanism of skeletal muscle strength or predict muscle behavior according to the relationship between muscle strength and contraction length by approaching the macro scale and micro scale to the middle.However,most of the models ignore the influence of the elastic characteristics of the half-sarcomere rich acid area.In this paper,the micro characteristics of the half-sarcomeres are introduced,and the active force model of the half-sarcomere cross bridge and the passive force model of the half-sarcomere rich acid area are established.The relationship between the half-sarcomere rich acid area and muscle strength is discussed in depth.Secondly,the statistical principle is introduced to explain the macroscopic characteristics of half-sarcomeres,and the statistical model of group half-sarcomeres is established,which reduces the huge calculation amount of traditional research methods for studying the collection of half-sarcomeres,and deeply explores the collective behavior of multiple half-sarcomeres at the macro level.Through comparative study,it is found that the actual group behavior of multiple half-sarcomeres is not exactly the same as the group behavior of a single half-sarcomere model after simple series connection.The effects of various proteins on the half-sarcomeres sometimes cause the non-uniformities of the half-sarcomeres.Finally,the simulation analysis of the half-sarcomere model in this paper is carried out,and the validity of the model is verified by comparing with the classical experimental data.The relationship between the non-uniformities of the half-sarcomeres and the interaction between actin and titin is obtained.The validity of the model is further verified by predicting the similarities and differences of the group behavior of different numbers of half-sarcomeres.