Beyond Human, or Just Really Amazing?

Biomechanics

“the application of the principles of physics to the analysis of movement”

Exercise Science, Ted Temertzoglou 2003

We might think of biomechanics as the “physics of human movement”

Biomechanics Examines the internal and

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

Aids in technique analysis and the development of innovative equipment designs

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

They all fall under the following 4 categories• Stability• Maximum Effort• Linear Motion• Angular Motion

The 7 Basic Principles of Biomechanics

• The lower the centre of mass, the larger the base of support, the closer the centre of mass to the base of support, and the greater the mass, the more stability increases.

Principle 1 – Stability

• The production of maximum force requires the use of all possible joint movements that contribute to the task’s objective.

Principle 2 – Maximum Force

• The production of maximum velocity requires the use of joints in order – from largest to smallest.

Principle 3 – Maximum Velocity

• The greater the applied impulse the greater the increase in velocity.

Principle 4 – Linear Motion

• Movement usually occurs in the direction opposite that of the applied force.

Principle 5 – Linear Motion

• angular motion is produced by the application of a force acting at some distance from an axis, that is, by torque. The application of torque produces changes in angular motion.

Principle 6 – Angular Motion

• angular momentum is consistent when an athlete or object is free in the air. Once an athlete is airborne, he or she will travel with a constant angular motion.

Principle 7 – Angular Momentum

• Planes– Sagital– Frontal, Coronal– Transverse

• Axis– Horizontal– Antereoposterior (Frontal)– Longitudinal (Vertical)

Review of Movements from Anatomy

Motion

• Kinematics– describing movements with respect to time and

space

• Kinetics– examines the forces that produce the movement

and result from the movement

Kinematics Variables

• Time: temporal characteristics of a performance, either of the total skill or its phases

• Displacement: length and direction of the path an athlete takes from start to finish

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

• Velocity: displacement per unit of time

• Angular Velocity: angular displacement per unit of time

• Acceleration: rate of change of velocity

• Angular Acceleration: angular velocity per unit of time

Kinetics Study of Motion

Internal Forces: generated by muscles pulling via

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

External Forces: acting from without, such as the

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

Focuses on the various forces that are associated with a movementFocuses on the various forces that are associated with a movement

Qualitative Analyses

It requires:

A framework within which skilled performance can be observed

A set of principles with which movement can be analyzed

A checklist to use when identifying errors

Techniques to use for error detection and correction

Involves obtaining information, visually or auditory, Involves obtaining information, visually or auditory, to assess performanceto assess performance

Quantitative Biomechanics

Involves measurement of variables that are Involves measurement of variables that are thought to optimize or maximize thought to optimize or maximize performanceperformance

Measuring Human Motion• Use the handout to plot a graph of the

movement involved in kicking a soccer ball.• This process involves QUANTIFYING human

movement for analysis!

Human Body Models

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

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

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

Rigid Segment Model: Used 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 body’s centre of mass

• The body is isolated from its surroundings

• The only external forces acting on the body are gravity and air resistance

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

Types of Motion

Linear motion Angular motionAngular motionGeneral motionGeneral motion

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

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

Rectilinear motion occurs when movement follows a straight line

Curvilinear motion occurs when the movement path is curved but also linear

Types of Motion

Identify the external forces acting on the human body

Describe the resulting motion

Describe the expected path and motion of any projectile

Differentiate between similar skills

Determine the degree of stability possessed by an athlete

Understand the causes and effects of actions

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

Objectives of Analyzing Human Motion:

Step 1 Identify the system to be studied, which is to separate the

object of interest from its surroundings

Step 2 Identify the frame of reference in which the movement

takes place

Step 3 Identify the type of motion that is occurring, the body

planes in which movement takes place (sagittal, frontal, or transverse), and

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

Preliminary Steps for Analyzing Human Motion