Chapter 2: Kinematic Concepts for

Analyzing Human Motion

Basic Biomechanics, 4th edition Susan J. Hall

Presentation Created by TK Koesterer, Ph.D., ATC Humboldt State University

Objectives •  Identify & describe reference positions,

planes, and axes associated with the human body

•  Provide examples of linear, angular, & general forms of motion

•  Define & appropriately use directional terms & joint movement terminology

•  Explain how to plan & conduct an effective qualitative human movement analysis

•  Identify & describe uses of available instrumentation for measuring kinematics

Forms of Motion

•  Most human movement is general motion

– A complex combination of

• Linear and

• Angular motion components

Forms of Motion

•  Linear Motion – May also be thought of as motion along a

line that may be straight or curved, with all parts of the body moving in the same direction at the same speed, also known as translatory motion, or translation.

• Rectilinear – along a straight line • Curvilinear – along a curved line

Forms of Motion

•  Angular motion – involving rotation around a central line or point

•  Axis of rotation – imaginary line perpendicular to the plane of rotation and passing through the center of rotation

General Motion

•  A combination of translation and rotation

•  Most human movement activities are categorized as general motion

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Mechanical Systems

•  Before determining the nature of a movement, the mechanical system of interest must be defined.

•  System – a body or group of bodies whose motion is being analyzed

Standard Reference Terminology Anatomical Reference Position

•  Erect standing position with all body parts, including the palms of the hands, facing forward; considered the starting position for body segment movements

Standard Reference Terminology Directional Terms

•  Superior

•  Inferior

•  Anterior

•  Posterior

•  Medial

•  Lateral

•  Proximal

•  Distal

•  Superficial

•  Deep

Standard Reference Terminology Anatomical Reference Planes

•  Cardinal planes – 3 imaginary perpendicular reference planes that divide the body in half by mass

– Sagittal plane

– Frontal plane

– Transverse plane

Standard Reference Terminology Anatomical Reference Axes

•  An imaginary axis of rotation that passes through a joint to which it is attached

– Mediolateral or frontal axis

– Anterioposterior or sagittal axis

– Longitudinal axis

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Joint Movement Terminology

•  In anatomical position, all body segments are considered to be positioned at zero degrees.

– Sagittal Plane Movements

– Frontal Plane Movements

– Transverse Plane Movements

•  Other Movements

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Sagittal plane movements

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Frontal Plane Movements

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Transverse Plane Movements

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Other Movements

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Spatial Reference Systems

•  Used to standardize the measurements taken

Cartesian Coordinate system

•  Movements primarily in a single direction, or planar, can be analyzed using a two-dimensional Cartesian

– X (horizontal) direction

– Y (vertical) direction

•  3-dimensional by adding a z-axis

Cartesian Coordinate System

Qualitative Analysis of Human Movement

•  Requires knowledge of the specific biomechanical purpose of the movement and the ability to detect the causes of errors

•  Qualitative refers to a description of quality without the use of numbers.

Prerequisite Knowledge for a Qualitative Analysis

•  Kinematics •  Performance outcome

Analysts should be able to distinguish the cause of a problem from symptoms of the problem or an unrelated movement idiosyncrasy

Experience in performing a motor skill does not necessarily translate to proficiency in analyzing the skill.

Planning a Qualitative Analysis

1.  What are major questions to be answered

2.  Determine the optimal perspective(s)

3.  Analyst’s viewing distance

4.  Number trial or executions

5.  Performer’s attire

6.  Nature of surrounding equipment

7.  Visual observation or video camera

Conducting a Qualitative Analysis •  Continuous process of;

–  formulating an analysis

– collecting additional observations

–  formulating an updated analysis

•  Detecting biomechanical errors

•  Characteristics of the performer

•  Other factors that can affect performance

•  Auditory information

•  Feedback from the Performer

•  Observation skill

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Tools for Measuring Kinematic Quantities

•  Cinematography & Videography

– Standard video 30 pictures per second

– Higher rates available

– Clarity of images

– Number of cameras to capture information

– Computer-linked equipment – digitizing

Measuring Kinematic Quantities

•  Other Movement Monitoring Systems

– Real-time tracking of LEDs

– Computer-linked cameras track targets

•  Other Assessment Tools

– Goniometer or Electrogoniometer

– Photocells, light beams, and timers

– Accelerometer

Summary

•  Teachers of physical activities, clinicians & coaches all routinely perform qualitative analyses to assess, correct, or improve human movements

•  Both knowledge of the specific biomechanical purpose of the movement and careful preplanning are necessary for an effective qualitative analysis

The End