1. 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

2. Kinematics Study of Motion
The study of time and space factors of a body in motion
The variables used to describe motion are time, displacement, velocity, and acceleration
These variables are used to describe both linear and angular motion (angular displacement, angular velocity, and angular acceleration)

3. Kinematics Variables
Time: a time interval calculated as the difference between the beginning and the end of two instants of time
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

4. Kinetics Study of Motion
Focuses on the various forces that are associated with a movement
Internal Forces:
generated by muscles pulling via their tendons on bones, and to bone-on-bone forces exerted across joint surfaces
Cause body segment movements
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
Affect total body movement

5. Types of Motion
Angular motion
General motion
Linear motion

6. Linear Motion
When all parts of the body move the same distance, in the same direction, at the same time
Refers to movement of the body as a unit without individual parts of the body moving relative to one another
Rectilinear motion occurs when movement follows a straight line
Curvilinear motion occurs when the movement path is curved

7. Angular and General Motion
Angular Motion (rotation)
Occurs when a body moves along a circular path, through the same angle, in the same direction, and at the same time
The axis of rotation is the point about which movement occurs
All joint motions are angular motions
General Motion
A combination of linear and angular motion
Includes most athletic and many everyday activities

8. Causes of Motion
The only cause of motion of the human body is the application of an internal or external force
Force is any action, a push or pull, which tends to cause an object to change its state of motion by experiencing an acceleration
Constant Velocity occurs when an object is not accelerating
Linear Motion is caused by forces which act through a body’s centre of mass
Angular motion is caused by forces that do not go through the centre of mass

9. Linear motion results when the forces
are applied through the centre of mass
Angular motion results when the forces are applied away from the centre of mass

10. Scalar and Vector Quantities
Scalar quantities have only magnitude
i.e. length of time to run 100m
speed posted on a road sign (100km/h)
Vector quantities have magnitude and direction (force)
- vectors are straight-line segments with one end defined
as the tail and the arrow tip defined as the head.
tail
head

11. Adding of Vectors
The head of a vector points in the direction of the quantity the vector represents
Vectors can be added together using the head to tail method
- to add vector B to vector A, an identical vector is drawn (same length and direction) as vector B beginning at the head of vector A
- the resultant vector is directed from the tail of vector A to the head of vector B and represents the acceleration of the person/object a b + b a =
Resultant
Resultant

12. Calculating net external force using free body diagrams

13. Levers
Simple machines that augment the amount of work done by an applied force
Axis/Fulcrum (A) - A rigid body (i.e., long bone) that rotates about a fixed point (i.e., joint)
Load (L) – Weight acting on the lever (i.e. weight of a limb segment)
Effort (E) – point initiating movement (i.e. Insertion point of muscle)
Three classes of levers:
a. first class (teeter-totter)
b. second class (wheelbarrow)
c. third class (shoveling snow)

15. Calculating Moments of Force
Moment arm is the (perpendicular) distance from the axis of rotation to where the force is being applied
Moment of force is the measure of a forces tendency to produce a rotation
influenced by the magnitude of moment arm and the magnitude of the force
Moment of Force = Moment Arm x Force
By grasping the wrench at the end (A) a greater torque is generated because the moment arm is greater than in (B)

16. Factors affecting the moment of forceD
A. Balanced teeter-totter
B. Increasing the moment arm by leaning backwards
C. Increasing the applied force by adding a friend

17. Mass and Inertia Concepts
Mass is the measure of how much matter an object has
Inertia is the reluctance of an object to change its state of motion from rest to moving, to moving faster, or to slowing down back to rest
Moment of inertia is a function of the mass of a rotating object and how its mass is distributed about its axis of rotation
The mass distribution of an individual about the longitudinal axis (A) and about a horizontal axis (B)

18. Centre of Mass
Centre of mass
outside of body
Located at the balance point of a body; a point found in or about a body where the mass could be concentrated
Generally, 15 cm above the pubic symphasis, or approximately 55% of standing height in females and 57% in males

19. Weight vs. Mass Mass - a measure of inertia
- measured in kilograms (kg)
Weight
- measure of the force of gravity (g)
- measured in Newtons (N)
- varies directly with the magnitude
of the acceleration due to gravity
(9.8 m/s2)
W = m x g