DPT 715: Kinesiology and Biomechanics Study Notes

Course Title: DPT 715 Kinesiology and Biomechanics of the Musculoskeletal System.
Core Curriculum Topics: * Posture. * Gait. * Basic biomechanical concepts. * Biomechanics of tissues and structures. * Biomechanics of Upper extremity joints. * Biomechanics of Lower extremity joints. * Biomechanics of Spine and Thorax.

Definition of Biomechanics: * Etymology: Derived from "Bio" (meaning Living) and "Mechanics" (meaning Forces and Effects). * Scientific Definition: The study of the structure and function of biological systems—including plants, humans, and animals—by applying the methods and principles of mechanics. * Interdisciplinary Nature: Biomechanics represents the application of multiple sciences, including: * Anatomy. * Physiology. * Neuroscience. * Engineering.
Definition of Kinesiology: * The comprehensive study of human movement, performance, and function.

Qualitative Analyses: * Definition: involve obtaining visual information to assess movement performance. * Essential Requirements: * A framework within which skilled performance can be observed. * A set of principles with which movement can be analyzed. * A checklist to use when identifying errors.
Quantitative Analyses: * Definition: Involves the direct measurement of variables regarding movement performance. * Technological Components: * Three-dimensional (3D) Kinematics: Uses high-speed motion capture to track each body segment. * Kinetics: Measures forces, moments, and power using force platforms. * Electromygrophy (EMG): Determines the sequence and timing of muscle activity.

Cardinal Planes of Motion: * Sagittal Plane: * Location: Vertically from the front to the back. * Suture Reference: Parallel to the sagittal suture of the skull. * Division: Divides the body into right/left or medial/lateral sections. * Frontal Plane (Coronal Plane): * Location: Vertically from the left to the right. * Suture Reference: Parallel to the coronal suture of the skull. * Division: Divides the body into front (anterior) and back (posterior) sections. * Transverse Plane: * Location: Horizontal to the body. * Reference: Parallel to the horizon. * Division: Divides the body into upper (superior) and lower (inferior) sections.
Degrees of Freedom (DOF): * Definition: Movement occurring in one plane; used to describe the type and amount of movement allowed by specific joints. * 1 DOF: Indicates a joint only moves in one plane. * DOF of the Arm Exercise: Analysis of available degrees of freedom from the shoulder to the wrist (excluding fingers).

Statics: The study of bodies at rest or in a state of equilibrium.
Dynamics: The study of moving bodies. * Kinematics: A branch of mechanics dealing with the motion of bodies without considering the forces that produce that motion. Key variables include displacement, joint angle, velocity, and acceleration. * Kinetics: A branch of mechanics that studies the forces producing motion or maintaining equilibrium. Key variables include force and torque (or moment of force).

Kinematic Definition: Describes the motion of a body segment without reference to the forces causing the motion. It focuses on movement amount, type, direction, and speed (or change in speed).
The Five Kinematic Variables for Segment Motion: 1. Type of Displacement: Includes linear, angular, or general. 2. Location of Displacement in Space: Typically located via the Cartesian Coordinate System ( $x$ -axis, $y$ -axis, and $z$ -axis) with the origin usually at the Center of Mass (COM). 3. Direction of Displacement: Considers positive and negative rotation around the three cardinal axes. * Local Coordinate System: Useful for joint-level function (e.g., motion of the tibia relative to the femur). * Global Coordinate System: Useful for functional activities (e.g., motion of the foot relative to the room). 4. Magnitude of Displacement: * Angular: Expressed in degrees ( $^{\circ}$ ) or radians. * Linear: Quantified by distance, typically measured in meters ( $m$ ). 5. Rate of Displacement: * Speed: Displacement per unit of time regardless of direction. * Velocity: Displacement per unit of time with a known direction. * Acceleration: The change in velocity per unit of time.

Linear Displacement (Translatory Motion): * The movement of a body in a straight line or along a straight pathway. * Human Application: Purely linear displacement is very rare in human motion and often includes a component of angular displacement.
Angular Displacement (Rotary Motion): * The movement of a body segment about an axis. * Cause: Produced when forces are applied away from the axis of rotation of a body.
General Motion: * A combination of rotary and translatory motion. * Instantaneous Center of Rotation (ICoR): Most joint rotations occur around a series of shifting centers of rotation rather than a static point. * Articular Constraints: The longer it takes for articular constraints to limit segment translation, the greater the shift of the ICoR during motion (e.g., comparing the knee joint to the elbow joint).

Direct Kinematic Measurement Tools: * Goniometers: Used for joint angles, though subject to source errors. * Electrogoniometers: Inexpensive and provide instant results, but are difficult to attach and have limited accuracy. * Accelerometers: Provide immediate results, but are fragile and prone to artifacts. * High-Speed Digital Video Cameras: Use latest technology to capture between $60$ and $10,000$ frames per second ( $fps$ ). These are expensive, ranging from $\$60,000$ to $\$150,000$ . * Optoelectric Systems: An active system where the subject wears tiny infrared lights picked up by cameras. * Advantages: No problem with marker labeling. * Disadvantages: Expensive, cumbersome, and time-consuming.
Gait Kinematics and Modeling: * Marker-Based Systems: At least $3$ markers are placed on a segment (e.g., thigh or shank) to form a plane and develop a reference coordinate system. * Direct Linear Transformation: A method using multiple cameras (Camera 1, Camera 2, Camera 3, Camera 4) to identify markers and construct a 3D image for determining the instantaneous relationship between coordinate systems. * Gait Cycle Data: Analysis typically tracks position through the STANCE and SWING phases, measured as a percentage of the gait cycle ( $0\text{ to }100\%$ ). Examples include ranges of Dorsiflexion (up to $30^{\circ}$ ) and Plantar Flexion (down to $-30^{\circ}$ ).