4


PART I FOUNDATION CONCEPTS


1.3 Describe movement directions, and explain the concept of degrees of freedom of movement. 1.4 Discern the differences between linear, angular, and general motion. 1.5 Illustrate the concepts of open and closed kinematic chain movement, and identify examples of these types of movement that occur in daily activities.


1.6 Discuss types of forces, and understand how internal and external forces can work to provide movement, stability, or dysfunction.


1.7 Explain the concepts of vector forces in terms of their magnitude and direction. 1.8 Outline the components of torques, and understand the relationship between forces, moment arms, and the torques they produce.


1.9 Define the concept of force couples in human motion.


Note to Students: It is recommended that you review the pretest questions before reading the chapter to better understand the critical elements of the text. As you complete each section, stop and answer the corresponding questions to test your comprehension. The pretest does not cover all the material in each chapter and should not be used as a sole means of self-assessment of knowledge.


The term kinesiology, from the Greek words kinein, meaning “to move,” and -logy, meaning “to study,” is the scientifi c study of movement and performance. Several branches of science, particularly anatomy, physiology, physics, and biomechanics, contribute to the science of kinesiology. Human anatomy lays the foundation by providing information about the structures of the body, and physiology outlines the interactions between these structures and various body systems. Physics describes the concepts of force and mass and their relationship in movement through the understanding of mechan- ics. Biomechanics applies the concepts of mechanics to human movement. The study of human kinesiology includes examination of human structures, study of the individual and collective functions of the joints, and understanding concepts related to forces that produce or prevent movement. To begin the study of human movement, this text


fi rst discusses universal terms to describe various types of movement and the directions and planes in which they occur. Motion can occur in linear paths and angular arcs, both of which are necessary for the accomplish- ment of daily activities. The way body segments move in relationship to each other determines their function and how tasks are accomplished. The legs function in two entirely different ways depending on whether the feet are on the fl oor when moving from sitting to standing or free from a surface when kicking a ball. For movement to occur, external forces such as those from gravitational forces and friction must be overcome by internal forces generated by the musculoskeletal system. Insight into how alignment and forces can either foster healing and increase function or cause injury and produce dysfunc- tion provides a foundation on which to build rehabilita- tion concepts and principles.


DIRECTIONAL TERMS


To describe and discuss anatomical structures and move- ment in a consistent manner, there is a universal reference or starting point: the anatomical position. This funda- mental reference depicts the human body in a standing position facing forward, arms at the side of the body, and the palms of the hands facing forward (Fig. 1.1). This position is the reference for describing anatomical struc- tures, planes of movement, and axes of rotation. In the anatomical position, structures and their rela- tionship to each other are described in standard directional terms. Medial and lateral are terms used to describe the relationship of a point to the midline of either the entire body or a body segment. A point closer to the midline is described as medial to other sites, whereas a site farther from the midline is described as lateral. Anterior and posterior reference the relationship between a location and the front (anterior) or back (posterior) of the body. When discussing the relationship between a site and the trunk, the terms proximal and distal are used. A site closer to the trunk than another site is considered proxi- mal; for example, the hip is proximal to the knee. Sites distal are further from the trunk. Superior and inferior describe structures in terms of being above or below another structure. The terms used to describe directions and examples using the terms are outlined in Table 1.1 and depicted in Figures 1.2 and 1.3. The terms cephalic and cranial can be used to describe positions closer to the head; caudal relates to positions closer to the feet. Superfi cial describes structures or areas that are closer to the surface, whereas deep refers to structures that are farther from the surface.


OSTEOKINEMATICS PLANES OF MOTION


The skeletal system moves through three-dimensional space as the body performs daily activities, such as rising


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