DEFINITIONS: 1. The study of mechanics in the human body is referred to as biomechanics. 2. The study of the effects of internal and external forces on the human body in movement and rest is called biomechanics. 3. Mechanical principles applied to the study of biological functions; the application of mechanical laws to living structures; the study and knowledge of biological function from an application of mechanical principles is called biomechanics. Axis : It is the line about which movement takes place. An imaginary straight line around which an object rotates is called axis. Plane : It is the surface which lies at right angles to axis and in which the movement take place. These terms are used to facilitate the description of movement or direction. Types of axes : They are 3 types of axes. a. Sagittal axis: It lies parallel to sagittal suture of skull, i.e. in a anterior-posterior direction. Movement at this axes occur in a frontal plane. b. Frontal or transverse axes: It lies parallel to transverse suture of skull. It is horizontal and at right angles to sagittal axes. Movement about frontal axes occurs in a sagittal plane. c. Vertical axes: It lies parallel to line of gravity. Movement about this axis is in a horizontal plane. Sagittal Frontal Vertical 2 EXERCISE THERAPY Planes: There are three planes. 1. Movement in horizontal plane (transverse plane): This plane divides the body into upper and lower halves. Movements in transverse plane occur parallel to ground. For example in rotation of the head, the nose moves parallel to ground. Rotatory movements in a transverse plane occur around a vertical axis of motion. Movement in the horizontal plane is not affected by gravity hence it is stated as gravity free movement. Weak muscles which unable to produce movement against gravity can often succeed in this plane. 2. Movement in frontal plane (coronal plane): the frontal plane divides the body into front and back halves. Movements in the frontal plane occur side to side movements such as bringing the head to each of the shoulders. Rotatory motion in the frontal plane occurs around an anterior posterior axis. 3. Movement in vertical plane (sagittal plane): An anteroposterior vertical plane passing through the body from front to back, dividing it in half. It is the plane that divides the body or body segment into the right and left parts. Movements in this plane include forward and backward motions such as nodding of the head. Rotatory motion in the sagittal plane occurs around a coronal axis. Frontal plane Sagittal plane Transverse plane MECHANICAL PRINCIPLES 3 KINEMATICS Kinematics is the area of biomechanics that include description of motion without regard for the forces producing it. They include. i. Types of motion. ii. Location of motion. iii. Direction of motion. iv. Magnitude of motion. (i) Types of motion: four types of motion are there. a. Rotatory motion: It is the movement of an object around a fixed axis in a curved path. Each point on the object or segment moves through the same angle at same distance. In human body the goal of most muscles appear to rotate a bony lever around a fixed axis. b. Translatory motion: