Download Angular Kinematics of Human Movement

Angular Kinematics of Human
Movement
Biomechanics and ergonomics
Objectives
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Define angular motion
angular motion
Tools for Measuring Body Angles
Relative versus Absolute Angles
Instant Center of Rotation
Angular motion
• Rotating body has axis of rotation
every point in the body moves in circle
around the axis of rotation
Observing the Angular Kinematics
• human movement involves rotation of one
or more body segments around the joints at
which they articulate.
• inferences of coordination of muscle
activity producing the joint actions can be
made
Observing the Angular Kinematics
• Clinicians, coaches, and
teachers of physical activities
routinely analyze human
movement
• Based on observation of
timing and range of motion
• Developmental stages of
motor skills are based on
analysis of angular kinematics
3 Stages of development in kicking
Angular Motion
• In angular motion, or rotational motion
around an axis, the axis of rotation is a line,
real or imaginary, oriented perpendicular to
the plane in which the rotation occurs, like
the axle for the wheels of a cart.
Angles
• An angle is formed by the intersection of
two lines, two planes, or a line and a plane.
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Measuring Angles
1. Filmed images
2. Videotapes and films of human movement
3. Computer software
Types of Angles
Two types
1. Absolute angle
2. Relative angle
Types of Angles
Relative angle:
• Anatomical reference position
Absolute angle:
• Horizontal reference
• Vertical reference
Relative angle
• Angle formed between the longitudinal axes
of adjacent body segments
• Relative angles should consistently be
measured on the same side of a given joint.
• The convention used for measuring relative
joint angles is that in anatomical reference
position, all joint angles are at 00.
Shoulder Flexion
Absolute angle
• Angular orientation of a body segment with
respect to a fixed line of reference.
• Absolute angles should consistently be
measured in the same direction form a
single reference – either horizontal or
vertical
Tools for Measuring Body Angles
1.Goniometer:
• One arm fixed to protractor at 00
• Other arm free to rotate
• Center of goniometer over joint center
• Arms aligned over longitudinal axes
• Accuracy depends positioning of goniometer
• Place marks on the skin
2-Electrogoniometer (elgon)
• A goniometer with an electrical potentiometer at
its vertex
3.Inclinometer: devices used for direct
assessment of human body segment angles
• Usually gravitationally based
Instant Center of Rotation
Instant Center:
Precisely located center of rotation at a joint at
a given instant in time
1)Roentgenograms (x rays)
2)Instrumented spatial linkage with pin
fixation
• The exact location of the instant center for a
given joint may be determined through
measurements taken from roentgenograms
(x rays), which are usually taken at 100
intervals throughout the range of motion at
the joint.
• An Instrumented spatial linkage involving
intracortical pin fixation has been used to
quantify relative linear and angular
movements at the knee.
• Example:
• The instant center
at the knee shifts
during angular
movement due to
accompanying
linear
displacements
between the femur
and the tibia in all
three planes.