Transcript Document

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