More Related Content
Similar to FW275 Biomechanics
Similar to FW275 Biomechanics (20)
More from Matt Sanders (20)
FW275 Biomechanics
- 2. © 2010 McGraw-Hill Higher Education. All rights reserved.
Exploring Biomechanics
Biomechanics: bio means “life”
Study of the actions of forces
Term first used 1970’s
Includes both internal forces produced by
muscles and external forces that act on the body
Biomechanics human movement is one sub
discipline of exercise science
- 3. © 2010 McGraw-Hill Higher Education. All rights reserved.
Exploring Biomechanics
Biomechanics
Academic backgrounds: zoology, medicine, engineering,
physical therapy
Common interest in biomechanical aspects of the structure
and function of living things
Undergraduate course
Usually requires prerequisite courses
Focusing on forces acting on the human body
Biomechanics commonly a quantitative field of study
Strong math, computer applications and problem solving
- 4. © 2010 McGraw-Hill Higher Education. All rights reserved.
History of Biomechanics
Aristotle (384-322 B.C.)
Archimedes (287-212
B.C.)
Galen (131-201 A.D.)
Leonardo da Vinci
(1452-1519)
Galileo (1564-1642)
Giovanni Alfonso Borelli
(1608-1679)
Isaac Newton (1643-1727)
Eadweard Muybridge
(1831-1904)
Julius Wolff (1836-1902)
Christian Wilhelm Braune
(1831-1892) & Otto
Fischer (1861-1971)
- 5. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Kinematics
Kinematics
The form, pattern, or sequencing of movement with
respect to time
Qualitative
Involving nonnumeric description of quality
Quantitative
Involving the use of numbers
Kinematic analysis often requires the use of both
visual description and quantitative measurement
- 6. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Kinematics
Kinematic quantities: distance, displacement,
speed, velocity, acceleration
Vector quantities have both size and direction
Displacement, velocity, acceleration
- 7. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Kinematics
Linear displacement
Change in linear position
- 8. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Kinematics
Angular displacement
Change in the angular position or orientation of a
line segment
- 9. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Kinematics
Angular--most human movement requires
angular quantities
Rotation around a central line or point
Primarily rotational motion occurs at joints
Linear velocity
Rate of change in linear position
Angular velocity
Angular displacement divided by the time interval
which displacement occurs
- 10. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Kinematics
Acceleration
Angular acceleration
Does not take into account particular
circumstances or rules when faced with a moral
problem
With every moral situation, there is a blank slate
and each case must be viewed independently
- 11. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Kinematics
Biomechanics use quantitative kinematics to
research differences between skilled performers
and non-athletes. Examples:
Runners stride length & frequency
Swimmer’s stroke rate & length
Track events velocity of takeoff
High jumpers vertical displacement
Basketball angle of projection, angle of release
Throwing events aerodynamics of flight path
Swinging (bat, racquet) timing, project speed and
angle
- 12. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Kinematics
Skilled performers move body segments at high
rate of angular velocity
Most biomechanical studies of human kinematics
involve non-athletes:
Infant through maternity developmental stages
Adapted P.E. kinematic patterns with motor disorders
Therapeutic uses to aid in recovery of
injuries/surgeries
- 13. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Kinematics
Quantitative kinematic analyses often use:
High-speed cinematography
videography
Reflective markers
Digitizing
- 14. © 2010 McGraw-Hill Higher Education. All rights reserved.
Kinetics
Study of the action of forces
Force
The product of mass and acceleration
Push or pull acting on a body
Vector quantity: magnitude, direction & point
of application to a body
Free body diagram
First step used when analyzing actions
Body, body segment or object of interest
Basic Biomechanics--Kinetics
- 15. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Kinetics
- 16. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Kinetics
Force rarely acts in isolation
Net force
Overall effect of many forces acting on a body
Vector sum of all the acting forces
Net force zero = acting forces balanced in
magnitude and direction
Net force present = body moves in the direction
of the net force with acceleration
- 17. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Kinetics
Torque
The rotary effect of a force
Torque quantified
The product of force (F) and the perpendicular
distance (d┴) from the force’s line of action to the
axis of rotation
T = F d┴
The greater the force, the greater the tendency for
rotation
- 18. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Kinetics
Inertia--Sir Isaac Newton
Tendency of a body to resist a change in its
state of motion
Resistance to acceleration
Inertia has no units of measurement
Amount of inertia a body possesses is
directly proportional to its mass
More massive an object is, the more it tends
to maintain its current state of motion
- 19. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Kinetics
1st
law of inertia
A Body will maintain a state of rest or
constant velocity unless acted on by an
external force that changes the state
A motionless object will remain motionless
unless there is a net force acting on it
- 20. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Kinetics
Inertia is influenced by mass (m) and
distribution of mass in the body
Mass distribution is characterized by the
radius of gyration (k)
- 21. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Kinetics
Newton’s 2nd
law--law of acceleration
A force applied to a body causes an acceleration of that body of a
magnitude proportional to the force, in the direction of the force, and
inversely proportional to the body’s mass
The greater the amount of force applied, the
greater the speed
F=ma
Angular motion, the law becomes:
When a torque acts on a body, the resulting angular
acceleration is in the direction of the torque and of a
magnitude inversely proportional to its moment of
inertia
- 22. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Kinetics
Newton’s 3rd
law--law of reaction
For every action, there is an equal and opposite
reaction
In terms of forces:
When one body exerts a force on a second, the
second body exerts a reaction force that is equal in
magnitude and opposite in direction on the first body
- 23. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Kinetics
Ground reaction forces
Are measured during gait, each contact the foot
makes with floor is analyzed
Walking, running patterns throughout development
stages using force platforms
Magnitude of the vertical component of the GRF
during running is generally two to three times the
runner’s body weight
Runner’s are classified as rearfoot, midfoot, or
forefoot strikers
- 24. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Kinetics
- 25. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Kinetics
GRF is an external force acting on the human
body
Magnitude and direction have implications for
performance in many sporting events
High jumper’s
Baseball pitching
Golf
- 26. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Kinetics
Friction is a force that acts at the interface of
surfaces in contact in the direction opposite
the direction of motion or impending motion
Units of force (N)
The size of the friction force is the product of
the coefficient of friction (µ) and the normal
(perpendicular) reaction force (R).
- 27. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Kinetics
Factors influencing the value of friction µ
Relative roughness and hardness of the surfaces
Type of molecular interaction between surfaces
Greater the molecular interaction, the greater
is the value of µ
- 28. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Kinetics
Normal reaction force (R)
Sum of all acting vertical forces (usually body’s
weight)
Altered magnitude R
Increased or decreased
When friction is altered, how does this change
motion?
- 29. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Kinetics
Altering the coefficient between two
surfaces can change friction
Use of gloves, thin wax…
Important daily influence to prevent
slippage
- 30. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Kinetics
Momentum (M) is a vector quantity
The quantity of motion that an object possesses
mechanical quantity important in collisions
Linear momentum
Product of an object’s mass and its velocity
Body with zero velocity has no momentum
What should the momentum be during most
weight training exercises?
- 31. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Kinetics
Impulse
Product of a force and the time interval over which
the force acts
Impulse = Ft
Impulse can change momentum
Impulse and momentum
Changes in momentum depend not only on the
magnitude of the acting external forces but also on
the length of time over which each force acts
When impulse acts on system, the result is a change
in the system’s total momentum
- 32. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Kinetics
Angular momentum (H)
Quantity of angular motion possessed by a body, measured as
the product of moment of inertia and angular velocity
H product of angular inertial property (moment of inertia) and
angular velocity
Linear momentum
Product of the linear inertial property (mass) and liner velocity
Liner motion: M – mv
Angular motion: H = Iw
or: H = mk2
- 33. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Kinetics
Factors affect magnitude of a body’s angular
momentum
Mass (m)
Distribution of that mass with respect to axis of rotation
Angular velocity of the body (w)
If body has no angular velocity; it has no angular
momentum
Mass or angular velocity increases; angular
momentum increases proportionally
- 34. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Kinetics
Factor that most dramatically influences angular
momentum
Distribution of mass with respect to the axis of rotation
Why?
Angular momentum is proportional to the momentum
result from multiplying units of mass, units of length
squared, and units of angular velocity
Kg ·m2
/s
- 35. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Kinetics
Angular impulse
Change in angular momentum equal to the
product of torque and time interval over which the
torque acts
Angular impulse generates a change in angular
momentum
- 36. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Fluid Mechanics
Fluid (interchangeably with liquid)
Is any substance that tends to flow or continuously
deform when acted on by a shear force
Both gases & liquids are fluids
Archimedes Principle
The magnitude of the buoyant force is equal to the
weight of the fluid displaced by the body
If magnitude of weight is greater than buoyant force,
the body sinks, moving downward in the direction of
the net force
- 37. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Fluid Mechanics
Buoyancy is studied in relation to floatation of
human body in water
Difference in floatability is function of body
density
Density of bone and muscle is greater than the
density of fat
What changes with floatation when a person
holds inspired air in the lungs?
- 38. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Fluid
Mechanics
Orientation of the body as it floats in
water is determined by the relative
position of the totally body center of
gravity relative to the total body center of
volume
What is center of gravity?
- 39. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Fluid
Mechanics
COG is the point around which the body’s
weight is balanced in all directions
Center of volume and Center of gravity vary
depending on body shape and size
- 40. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Fluid
Mechanics
Drag
Generally, a resistance force:
A force that slows the motion of a body moving
through a fluid
Theoretical square law
The magnitude of the drag force increases approx
with the square of velocity
Effect seen with high velocity sports: cycling, speed
skating, downhill skiing, bobsled, luge
3 types of drag
Skin friction/surface drag
Form drag/profile drag
Wave drag
- 41. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Fluid
Mechanics
Form drag
- 42. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Fluid
Mechanics
Wave drag
- 43. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics--Fluid
Mechanics
Force that acts perpendicular to fluid flow is
lift
Lift can assume any direction (not just
vertically upward)
Determined by direction of fluid flow and
orientation of body
Can be generated by foil
Shape capable of generating lift in the presence of a
fluid flow
Human hand during swimming
- 44. © 2010 McGraw-Hill Higher Education. All rights reserved.
Basic Biomechanics
The study of biomechanics covers
many other topics that help us to
better understand human
movement in relation to forces
acting on the body, joint
movements and forms of motion
- 45. © 2010 McGraw-Hill Higher Education. All rights reserved.
Professional Organizations
Advantageous for students to consider
student memberships with professional
organizations in their chosen field of sport
science study
Biomechanics has many supported journals
Memberships include discounts: journal
subscriptions, conference fees and
opportunities for students to interact with
professionals
- 46. © 2010 McGraw-Hill Higher Education. All rights reserved.
Professional Organizations
American Society of Biomechanics
Canadian Society of Biomechanics
European Society of Biomechanics
International Society of Biomechanics
International Society of Biomechanics in Sport
Mulit-disciplinary organizations
American College of Sports Medicine
American Alliance for Health, Physical Education,
Recreation and Dance
- 47. © 2010 McGraw-Hill Higher Education. All rights reserved.
Careers
What are some potential career opportunities
in biomechanics?