A beginner's guide to understanding muscle function based on origins and insertions

DOI
  • Kawamata Seiichi
    Graduate School of Biomedical & Health Sciences, Hiroshima University
  • Kurose Tomoyuki
    Graduate School of Biomedical & Health Sciences, Hiroshima University
  • Ozawa Junya
    Department of Rehabilitation, Faculty of Rehabilitation, Hiroshima International University
  • Sakakima Harutoshi
    School of Health Sciences, Faculty of Medicine, Kagoshima University

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Other Title
  • 筋の起始と停止から作用を理解するための考え方入門

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Description

This paper describes a process through which students can begin to understand skeletal muscle function. Muscles shorten when they contract, which results in the insertion being pulled towards the origin. Since muscle contractions induce movement(s) at the joint(s) between the origin and insertion, movement is restricted by the mobility of the joint(s). Joint movement is often three-dimensional and can be divided into the following 3 types: flexion/extension, adduction/abduction, and internal rotation/ outer rotation (medial rotation/lateral rotation). To make analyses of movement easier, these 3 types of movement should be analyzed separately by applying the principle of leverage. Essentially, muscle function involves movements that minimize the distance between the origin and insertion at the three dimensional level. Therefore, the movement of a muscle can be predicted based on the locations of its origin and insertion and the mobility of the joint(s) between its origin and insertion. As representative examples, this study describes detailed analyses of the movement of the supraspinatus, infraspinatus, latissimus dorsi, levator scapulae, serratus anterior, and gluteus medius and minimus muscles. Regarding muscle origins and insertions, it should be noted that muscles located in the same part of the body tend to have common origins/insertions, innervations, and similar functions, and such muscles are referred to as a muscle group (e.g., the muscles in the anterior forearm, posterior thigh, the hamstrings, and the adductor group). As the human body contains numerous skeletal muscles, when students start to study muscle functions, they should first learn the common features of a given muscle group, such as its origin, insertion, innervations, and functions, before proceeding to learn the characteristics of individual muscles.

Journal

  • Structure and Function

    Structure and Function 14 (2), 62-74, 2016

    Co-medical Research Society of Structure and Function

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