• Define commonly used anatomic and kinesiologic terminology. • Describe the common movements of the body. • Differentiate between osteokinematic and arthrokinematic movement. • Describe the arthrokinematic principles of movement. • Analyze the planes of motion and axes of rotation for common motions. • Describe how force, torque, and levers affect biomechanical movement. • Describe the three biomechanical lever systems, and explain their advantages and disadvantages. • Analyze how muscular lines of pull produce specific biomechanical motions. • Explain how muscular force vectors are used to describe movement. Movement of the entire human body is generally described as a translation of the body’s center of mass, or center of gravity (Figure 1-3). An activity such as walking results from forward translation of the body’s center of mass, thus the entire body. It is interesting to note, however, that movement or translation of the entire body is powered by muscles that rotate the limbs. This concept is illustrated in Figure 1-4, which shows an individual running (anterior translation of the center of mass) as a result of muscles rotating the legs around the axis of rotation of each hip. It is important to note that the functional movement of nearly all joints in the body occurs through rotation. • Anterior: Toward the front of the body • Posterior: Toward the back of the body • Midline: An imaginary line that courses vertically through the center of the body • Medial: Toward the midline of the body • Lateral: Away from the midline of the body • Superior: Above, or toward the head • Inferior: Below, or toward the feet • Proximal: Closer to, or toward the torso • Caudal: Toward the feet (or “tail”) • Superficial: Toward the surface (skin) of the body • Deep: Toward the inside (core) of the body • Origin: The proximal attachment of a muscle or ligament • Insertion: The distal attachment of a muscle or ligament • Prone: Describes the position of an individual lying face down • Supine: Describes the position of an individual lying face up Osteokinematics describes the motion of bones relative to the three cardinal planes of the body: sagittal, frontal, and horizontal (Figure 1-6) (Box 1-1). • Sagittal plane: Divides the body into left and right halves. Typically, flexion and extension movements occur in the sagittal plane. • Frontal plane: Divides the body into front and back sections. Nearly all abduction and adduction motions occur in the frontal plane. • Horizontal (transverse) plane: Divides the body into upper and lower sections. Nearly all rotational movements such as internal and external rotation of the shoulder or hip and rotation of the trunk occur in the horizontal plane. Axes of Rotation and Associated Movements Degrees of freedom refers to the number of planes of motion allowed at a joint. A joint can have 1, 2, or 3 degrees of angular freedom, corresponding to the three cardinal planes (see the earlier section on terminology). As depicted in Figure 1-7, for example, the shoulder has 3 degrees of freedom, meaning the shoulder can move freely in all three planes. The wrist, on the other hand, allows motion in two planes, so it is considered to have 2 degrees of freedom. Joints such as the elbow (humeroulnar joint) allow motion in only one plane and therefore are considered to have just 1 degree of freedom. Rotation describes the movement of a bony segment (or segments) as it spins about its longitudinal axis of rotation. For example, turning the head or turning the trunk side-to-side are considered rotational movements (Figure 1-10, A). Motions of the extremities can be further classified into internal and external rotation. Internal rotation describes the motion of a bony segment that results in the anterior surface of the bone rotating toward the midline. External rotation involves rotation of the anterior surface of a bone rotating away from the midline (Figure 1-10, B).
Basic Principles of Kinesiology
Kinematics
Terminology
Osteokinematics
Planes of Motion
Axis of Rotation
Table 1-1
Axis of Rotation
Plane of Motion
Examples of Movement
Anterior-posterior
Frontal
Hip abduction-adduction
Shoulder abduction-adduction
Medial-lateral
Sagittal
Elbow flexion-extension
Knee flexion-extension
Vertical or longitudinal
Horizontal
Shoulder internal-external rotation
Rotation of the trunk
Degrees of Freedom
Fundamental Movements
Rotation
Basic Principles of Kinesiology
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