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CHAPTER 22: INSTRUMENTATION FOR MOTION ANALYSIS KINESIOLOGY Scientific Basis of Human Motion, 12th edition Hamilton, Weimar & Luttgens Presentation Created by TK Koesterer, Ph.D., ATC Humboldt State University Revised by Hamilton & Weimar McGraw-Hill/Irwin Copyright © 2012 by The McGraw-Hill Companies, Inc. All rights reserved. Objectives 1. Identify and describe instrumentation for the collection and analysis of kinematic data in human movement. 2. Identify and describe instrumentation for the collection and analysis of kinetic data in human movement. 3. Describe the limitations of biomechanical instrumentation. 4. Critically examine the research literature in the field of human movement with an understanding of the methodologies used. 22-2 Instrumentation for Kinematic Analysis Data that describe a motion are collected with a variety of instruments: Video. High-speed cameras. Sophisticated motion tracking systems. Primary purpose is to enable people to analyze motion beyond the capabilities of their own physical senses. 22-3 Instrumentation for Kinematic Analysis Still cameras: multiple images on a single picture. Flashing strobe light. Taken in a dark room with an open shutter. Motion appears as a series of still shots. Fig 17.7 22-4 Instrumentation for Kinematic Analysis Auto-advance cameras: Allows rapid film advancement and exposure. Fig 22.1 22-5 Instrumentation for Kinematic Analysis High-speed cameras: Speed of 500 to 20,000 frames per second. Provides ample number of clear data points for analyzing the fastest of human motions. Historically, a projector that permitted single frame projection was required so that measurements could be made of the image. 22-6 Instrumentation for Kinematic Analysis Digitizing: The term “digitize” simply means that specific data points from each frame are recorded (usually by computer) as pairs of x and y coordinates. Fig 22.6 22-7 Instrumentation for Kinematic Analysis Video: Usually uploaded to a computer. May also be digitized. Two-dimensional or three-dimensional systems available. 3-D systems require more cameras and synchronization. 22-8 Basic Photoinstrumentation Procedures Basic measurements in kinematics are time and displacement (both angular and linear). Maximum accuracy of these measurements is important. 22-9 Time Based on the frame rate, or the rate at which images are photographed. Home video: 30 frames/sec. High-speed cameras: up to 20,000 frames/sec. Frame rate should be determined according to the speed at which an activity is performed. Faster performance, higher frame rate. Offers more detailed analysis. 22-10 Displacement Camera placement: 2-D - perpendicular to the plane of motion. Scale reference is used for calibration. Fig 22.5 22-11 Other Photoinstrumentation Procedures Camera must be absolutely level and still. a tripod and level are used. More light is required with higher shutter speeds. Markers on joints and body parts. Fig 17.6 22-12 Optoeletronic Systems Subject marked with light emitting diodes (LEDs). Cameras are sensitive to light sources and transmit their location in space to a computer as a series of x & y coordinates. Kinematic calculations are done based on changes in these coordinates. 22-13 Optoeletronic Systems Pictorial output usually is a stick figure. Fig 22.3 22-14 Three-Dimensional (3D) Systems Camera systems configured to collect data in three planes. Simplest method is to position two cameras with axes perpendicular. Cameras must be carefully synchronized. System must be calibrated in 3D using a cube or a multi-armed device. Direct linear transformation is used for conversion of 2D pictures to a 3D image. 22-15 Real Time Systems Motion tracking system that operates in real time. Similar to virtual reality simulations. Currently light based or electromagnetic in nature. 22-16 Electrogoniometer (elgon) and Accelerometer Elgon is a double-arm goniometer with a potentiometer for an axis. Angular displacement measured by changes in electrical current. Accelerometer measures linear acceleration. Global positioning satellite receivers (GPSr) also useful for time and distance data on a larger scale. Fig 22.7 22-17 Instrumentation for Kinetic Analysis Usually collected through the use of: Dynamometers: spring and cable tension instruments that measure static muscle strength. grip strength dynamometer Force transducers: one type is a strain gauge - altered resistance due to strain produces a change in output voltage that can be recorded. 22-18 Adaptable Pressure Sensing Materials Piezo electric film and force sensing resistors (FSRs). Variety of sizes. Connected to a computer through an analog to digital converter. Fig 22.8 22-19 Force Plate Senses ground reaction forces. Walking, running, jumping, landing, etc. Linear forces and torques acting at the point of impact are identified. 22-20 Electromyography (EMG) Electrical activity (action potentials) from the muscles are sensed by surface or indwelling electrodes. Signal is amplified and transmitted to a recording device. Quantitative analysis by “normalizing” the EMG output. Fig 22.10 22-21 Computer Models and Simulation Kinematic, kinetic, and EMG data are compiled and synthesized into mathematical computer models. Allows for exploration of movement without endangering humans. Fig 22.11 22-22 Computer Simulations Used to predict limits of human performance. Fig 22.12 22-23 Skeletal Muscle Simulation PE = Parallel elastic component SE = Series elastic component CE = Contractile element Fig 22.13 22-24 Using Quantitative Analysis There should be some clear purpose in mind when one sets out to collect movement data. This purpose will determine: Type of data collected. Methodology for collection. Instrumentation for collection. The analysis should be aimed toward some end result. 22-25 Optimization of Performance All factors that make up the motion are combined in such a way as to produce the most effective result. The goal of much of the quantitative biomechanical analysis is to Provide a mathematical description of the relationship between various factors that comprise the performance. 22-26 Injury Prevention Injuries are often the result of forces applied in excessive or inappropriate ways. Quantitative data collection can provide valuable information about the risk of injury in any movement. 22-27 Rehabilitation In most therapeutic and rehabilitation settings, quantitative data are collected on patients on a regular basis. These data are then compared with models of normal patterns, and from these comparisons, programs of rehabilitation and remediation are designed. 22-28