how do i move? chapter 8 the science of biomechanics

How Do I Move?Chapter 8

The Science of BiomechanicsThe Science of Biomechanics

Sport Books Publisher 2

Objectives: Identify the external forces acting on the human body.Identify the external forces acting on the human body.

Describe the resulting motion.Describe the resulting motion.

Describe the expected path and motion of any projectile.Describe the expected path and motion of any projectile.

Differentiate between throw-like and push-like skills.Differentiate between throw-like and push-like skills.

Determine the degree of stability possessed by an athlete.Determine the degree of stability possessed by an athlete.

Understand the causes and effects of somersaulting.Understand the causes and effects of somersaulting.

Qualitatively analyze simple sport skills that involve Qualitatively analyze simple sport skills that involve throwing, striking, or hitting an object.throwing, striking, or hitting an object.


Biomechanics

Examines the internal and Examines the internal and external forces acting on the external forces acting on the human body and the effects human body and the effects produced by these forces.produced by these forces.

Aids in technique analysis and Aids in technique analysis and the development of innovative the development of innovative equipment designs.equipment designs.

Draws on knowledge from Draws on knowledge from sports medicine, physical sports medicine, physical therapy, kinesiology, and therapy, kinesiology, and biomechanical engineering.biomechanical engineering.


Quantitative Analyses

For ExampleFor Example::

Pattern of forces using a force Pattern of forces using a force platformplatform

Sequence of muscle activity Sequence of muscle activity using electromyography (EMG)using electromyography (EMG)

Three-dimensional (3D) Three-dimensional (3D) movements of each body movements of each body segment using high speed segment using high speed cinematographycinematography

Involves measurement of variables that are thought to optimize Involves measurement of variables that are thought to optimize or maximize performanceor maximize performance

golf swing


Qualitative Analyses

It requires:It requires:

A framework within which skilled A framework within which skilled performance can be observed performance can be observed

A set of principles with which A set of principles with which movement can be analyzed movement can be analyzed

A checklist to use when identifying A checklist to use when identifying errorserrors

Techniques to use for error detection Techniques to use for error detection and correctionand correction

Involves obtaining visual or aural information to asses Involves obtaining visual or aural information to asses performanceperformance


Kinematics Study of Motion The study of time and space The study of time and space

factors of a body in motion.factors of a body in motion.

The variables used to The variables used to describe motion are time, describe motion are time, displacement, velocity, and displacement, velocity, and acceleration.acceleration.

These variables are used to These variables are used to describe both linear and describe both linear and angular motion (angular angular motion (angular displacement, angular displacement, angular velocity, and angular velocity, and angular acceleration).acceleration).


Kinematics Variables TimeTime:: temporal characteristics of a performance, either of the temporal characteristics of a performance, either of the

total skill or its phasestotal skill or its phases

DisplacementDisplacement:: length and direction of the path an athlete takes length and direction of the path an athlete takes from start to finishfrom start to finish

Angular DisplacementAngular Displacement:: direction of, and smallest angular direction of, and smallest angular change between, the rotating body’s initial and final positionchange between, the rotating body’s initial and final position

VelocityVelocity:: displacement per unit of time displacement per unit of time

Angular VelocityAngular Velocity:: angular displacement per unit of time angular displacement per unit of time

AccelerationAcceleration:: rate of change of velocity rate of change of velocity

Angular AccelerationAngular Acceleration:: angular velocity per unit of time angular velocity per unit of time


Kinetics Study of Motion

Internal Forces:Internal Forces: Generated by muscles pulling via their Generated by muscles pulling via their

tendons on bones, and to bone-on-tendons on bones, and to bone-on-bone forces exerted across joint bone forces exerted across joint surfacessurfaces

External Forces:External Forces: Acting from without, such as the force Acting from without, such as the force

of gravity or the force from any body of gravity or the force from any body contact with the ground, environment, contact with the ground, environment, sport equipment, or opponentsport equipment, or opponent

Focuses on the various forces that are associated with a Focuses on the various forces that are associated with a movementmovement


Human Body Models

Particle Model:Particle Model: Used when the object of interest (the human body Used when the object of interest (the human body

or an object) is airborne after being thrown, or an object) is airborne after being thrown, struck, or kickedstruck, or kicked

Stick Figure Model:Stick Figure Model: Used when the object is in contact with its Used when the object is in contact with its

environmentenvironment

Rigid Segment Model:Rigid Segment Model: Used for more sophisticated quantitative analysesUsed for more sophisticated quantitative analyses


Three models used to represent the diver

Particle Model

Stick Figure Model Rigid Segment Model


Particle Model

The drawing consists of a single point, representing The drawing consists of a single point, representing the body’s center of massthe body’s center of mass

The body is isolated from its surroundingsThe body is isolated from its surroundings

The only external forces acting on the body are The only external forces acting on the body are gravity and air resistance (when a large velocity is gravity and air resistance (when a large velocity is involved)involved)

Limited to bodies that are in flight Limited to bodies that are in flight (projectile (projectile motion)motion)


Preliminary Steps for Analyzing Human Motion

Step 1Step 1

Identify the system to be studied, which is to separate the Identify the system to be studied, which is to separate the object of interest from its surroundings.object of interest from its surroundings.

Step 2Step 2

Identify the frame of reference in which the movement Identify the frame of reference in which the movement takes place.takes place.

Step 3Step 3

Identify the type of motion that is occurring, the body Identify the type of motion that is occurring, the body planes in which movement takes place (sagittal, frontal, or planes in which movement takes place (sagittal, frontal, or transverse).transverse).

Identify the axes of rotation about which rotational motion Identify the axes of rotation about which rotational motion occurs (sagittal, frontal, or vertical).occurs (sagittal, frontal, or vertical).


Types of Motion

Linear motionLinear motion Angular motionAngular motionGeneral motionGeneral motion


Curvilinear Motion

When all parts of the body move the same When all parts of the body move the same distance, in the same direction, at the same time distance, in the same direction, at the same time

TranslationTranslation refers to movement of the body as a refers to movement of the body as a unit without individual segment parts of the body unit without individual segment parts of the body moving relative to one anothermoving relative to one another

Rectilinear motionRectilinear motion occurs when movement occurs when movement follows a straight line follows a straight line

Curvilinear motionCurvilinear motion occurs when the movement occurs when the movement path is curvedpath is curved


Angular and General MotionAngular Motion (rotation)Angular Motion (rotation) Occurs when a body moves along Occurs when a body moves along

a circular path, through the same a circular path, through the same angle, in the same direction, and angle, in the same direction, and at the same timeat the same time

The axis of rotationThe axis of rotation is the point is the point about which movement occursabout which movement occurs

All joint motions are angular All joint motions are angular motionsmotions

General MotionGeneral Motion

A combination of linear and A combination of linear and angular motionangular motion

Includes most athletic and many Includes most athletic and many everyday activitieseveryday activities

how do i move? chapter 8 the science of biomechanics

Documents

bone forces

body segment

pattern of forces

body contact

various forces

sport equipment

smallest angular change

joint surfacesexternal