Chapter 11 Angular Kinematics of Human Movement

1
Chapter 11Angular Kinematics of Human Movement

• Basic Biomechanics, 4th edition
• Susan J. Hall
• Presentation Created by
• TK Koesterer, Ph.D., ATC
• Humboldt State University

2
Objectives

• Distinguish angular motion from rectilinear and
  curvilinear motion
• Discuss the relationship among angular kinematic
  variables
• Correctly associate associate angular kinematic
  quantities with their units of measure
• Explain the relationship between angular and
  linear displacement, angular and linear velocity,
  and angular and linear acceleration
• Solve quantitative problems involving angular
  kinematic quantities and the relationship between
  and linear quantities

3
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

4
Measuring Angles

• Filmed images
• Videotapes and films of human movement
• Computer software

5
11-1
6
Relative versus Absolute Angles

• Relative angle
• Anatomical reference position
• Absolute angle
• Horizontal reference
• Vertical reference

7
11-2
8
11-3
9
Tools for Measuring Body Angles

• Goniometer
• One arm fixed to protractor at 00
• Other arm free to rotate
• Center of goniometer over joint center
• Arms aligned over longitudinal axes
• Electrogoniometer (elgon)
• Inclinometers

10
Instant Center of Rotation

• Instant Center
• Roentgenograms (x rays)
• Instrumented spatial linkage with pin fixation
• Example
• Instant center of the knee shifts during angular
  movement

11
11-4
12
Angular Kinematic RelationshipsAngular Distance
Displacement

• Assessed as difference of initial final
  positions
• Counterclockwise is positive
• Clockwise is negative
• Humans also indicate with joint-related
  terminology
• Measured in
• Degrees, radians, or revolutions

13
Radian
14
Angular Kinematic Relationships Angular Velocity

• Angular velocity angular displacement ? ?
• change in time ?t
• Units deg/s, rad/s, rev/s, rpm

15
Angular Kinematic Relationships Angular
Acceleration

• Angular acceleration change in angular velocity
• change in time
• ? ? ?
• ?t
• Units deg/s2, rad/s2, rev/s2

16
Angular Kinematic Relationships

• Angular Motion Vectors
• Right hand rule
• Average vs. Instantaneous Angular Quantities
• Angular speed, Velocity, Acceleration

17
Right Hand Rule
18
Relationship Between Linear and Angular Motion

• d r?
• Radius of rotation
• Linear distance radius of rotation same units
• Angular distance in radians

19
Radius of Rotation
20
Linear and Angular Velocity

• V r? m/s (m) (rad/s)
• With all other factors held constant, the greater
  the radius of rotation at which a swinging
  implement hits a ball, the greater the linear
  velocity imparted to the ball
• However, the magnitude of the angular velocity
  figures as heavily as the length of the radius of
  rotation in determining the linear velocity of a
  point on a swinging implement

21
Linear and Angular Acceleration

• Tangential acceleration
• at v2 - v1 / t
• at r?
• Radial acceleration
• ar v2 / r

at
ar
22
Summary

• The angular kinematic quantities - angular
  displacement, angular velocity, and angular
  acceleration - possess the same interrelationship
  as their linear counterparts
• Angular kinematics variables may be quantified
  for the relative angle formed by the longitudinal
  axes of two body segment articulating at a joint,
  or for the absolute angular orientation of a
  single body segment with respect to a fixed
  reference line

23
The End