1. Basic
Biomechanics for Sport
Sciences
Introduction
Aj.Sirinart Laibsirinon
Department of Physical Therapy
Faculty of Allied Health Sciences
2/2554

2. Basic knowledge required prior to
biomechanics class
 Skeletal system: bone & joint
 Muscular system: muscle, tendon &
ligament
 Anatomical position &
terminology
 Anatomical plane & axis
 Joint Motion and terminology

3. A…………….…..
B…………….…. D…………….…
C…………………. ..
.
E…………….….
.
F…………….….
.
G…………….…
..
H…………….…
S…………….…..
..
I…………….….. T…………….…..
K……………. U…………….…..
…..
L…………..
N……..…..
V………...
W………..
X……..…..
Y ……………
Z ……………
AA……………

5. The muscular system

6. Anatomical position
The human body standing erect with palms turned forward, used as the
position of reference in designating the site or direction of structures of

7. Anatomical
position

9. Anatomical Directional Terminology
• Anterior : in front or in the front part
• Posterior : behind, in back or rear.
• Lateral : on or to the side, outside, away from
center
• Medial : towards the middle or median
• Superior : above in relation to another structure
• Prone : face down
• Supine : face up
• Distal : situated away from centre
• Proximal : situated towards centre
• Dorsal : relating to back, posterior
• Terms can be combined e.g. posterioinferior- behind and
below

10. Anatomical Planes
Anatomical plane

11. Frontal or Sagittal plane Transverse or
coronal plane horizontal
plane

12. 1.Frontal or B
Coronal A
Plane
2. Transverse
or horozontal C
Plane
3.Sagittal
Plane

13. Frontal or
Sagittal Plane
Coronal
Plane
Transverse or
horozontal
Plane

14. Joint
1. Neck, Lumbar or spine
2. Shoulder
3. Elbow
4. Wrist & finger
5. Hip
6. Knee
7. Ankle*****

15. Anatomical Planes: Joint Motion
1.Frontal or Coronal Plane:
Abduction /Adduction
Inversion /eversion
Lateral flexion
2. Sagittal Plane:
Flexion /Extension
Dorsiflexion
/plantarflexion
3. Horizontal Plane:
Internal or medial rotation /
external or lateral rotation
Abduction /Adduction
**** Ankle joint)
Neck & Trunk

16. External
Internal rotation

17. Abduction
Adduction

20. Overview: Basic
Biomechanics
 Definition of biomechanics
 Kinematics, Kinetics, Anthropometric, Kinesiol
ogy
 Purposes of studying biomechanics
 Levers & theirs classification
 Laws of motion and their influence on sport
movement
 Equilibrium, balance, & stability
 Factors influencing balance

21. What is Biomechanics?
 Bio= life
 Mechanics= physical actions
branch of physics that analyzes the actions
of forces on particles and mechanical systems
 Eg. Newton law: F = ma
 Biomechanics:
‘ Biomechanics is the science concerned
with the internal and external forces acting
on a human body and the effects produced
by these forces’
Hay (1993) The Biomechanics of Sports
Techniques. Prentice Hall Publishers

23.  Kinesiology: study of human movement

24. Sub-branch of Mechanics?
 Majors sub-branch of Mechanics
 Statics: form of mechanics that analyzes systems
in constant state of motion
 Could be no movement at all
 Could be constant velocity with no acceleration
 Dynamics: form of mechanics that analyzes
systems in motion and accelerating

26. Types of Biomechanics?
 Major types of Biomechanics
 Kinematics: description of motion, including
the pattern and speed of movement
(appearance of motion)
 swing
 clean & jerk clean

27. Types of Biomechanics?
 Major types of Biomechanics
 Kinetics: study of the forces associated with
motion
 ??? biceps


29. Tools for biomechanical
analysis

30. Anthropometric
 Related to the dimensions (size and shape) and
weights of the body segments
?????
A B C

31. ?????
A B
C

32. What does biomechanics have to
do with anatomical kinesiology?
 Anatomical kinesiology is the what
 Muscle origins, insertions, and
actions
 Biomechanics is the how
 Mechanical principles that dictate
the manner those muscles work

33. Why study biomechanics
 Foundational understanding of mechanical principles
and how they can be applied in analyzing movements of
human body
 What if the biomechanical principle behind variable
resistance exercise machine?
 Why you have to do weight lifting slowly if strength
is the main focus?
 What is the safest way to lift heavy weight?
 At what angle should a ball be thrown fro maximum
distance?

34. Purposes of studying
Biomehanics
 Increase
performance
 Increase speed
 Increase strength
 Increase power
 Improve sport skill
 Minimize risk of
injury (primarily

35. Levers
 What do levers have to do with human movement?
 EVERYTHING!
 Levers are rigid bars (in the body, bones) that move
around an axis of rotation (a joint) or fulcrum
 Forces (supplied by muscles) cause the movement
to occur

36. Lever Functions
 Magnify a force
 A simple crowbar
 Increase speed and range-of-motion
(ROM)
 Small amount of muscular contraction
proximally can produce lots of
movement distally: Deltoid

37. Lever Functions
 Balance torques
 A triple beam scale
 Change direction of force
 A seesaw
 a pulley of a weight machine

38. Lever Arm Length
Definitions
Resistance Arm: distance between axis
and point of resistance application
Force Arm: distance between axis and
point of force
Force arm Resistance arm

39. Lever Types
 First, second, and third class
 Arrangement of
 the effort or muscle force,
 the fulcrum or axis
 the resistance determines the
classification
 Classification determines the lever’s
strengths and weaknesses

40. First Class
 Force or effort >> Fulcrum or Axis
>>Resistance or load
 About 25% of the muscles in your body
operate as first class levers

41. First Class

42. R
F:  when axis close to
resistance, produces
power
F: Axis
R
Axis
 When axis close to
force or
effort, produces speed
and ROM

43. Second Class
 Axis >> Resistance>> Force or effort
 Very few occurrences in the body
 Gain resultant force (you can lift
more), lose distance

44. Second Class

45. Second Class

47. Gastronomies
muscle
Force
contraction force
BW
Resist.
Axis
Axis

48. Third Class
 Resistance >> Force or effort >>Axis or
Fulcrum
 As much as 85% of the muscles in the body
function as third class levers
 Usually produce speed at the expense of force
 Greater lever length = greater speed

49. Third Class

50. Bicep force
Elbow joint
Hand weight

52. 1st Class 2nd Class 3rd Class

53. Exercise 1: indicate
- Axis, Muscle force, Resistance
- What lever class?

54. Third class

55. Exercise 2: indicate
- Axis, Muscle
force, Resistance
- What lever class?

56. Force: Quadriceps
Axis: Knee joint
Resistance
Third class

57. Exercise 3: indicate
- Axis, Muscle
force, Resistance
- What lever class?

58. Axis: ?
Muscle force: ?
Resistance: ?

59. Laws of Motion
 Inertia
 Acceleration
 Reaction

60. Law of Inertia
(Newton’s First Law)
 “A body in motion tends to stay in motion at the
same speed in a straight line unless acted upon
by a force; A body at rest tends to remain at rest
unless acted upon by a force”
 English translation: unbalanced forces cause
motion; Balanced forces don’t change anything

61. Law of Inertia
(Newton’s First Law)
 Mass is the measure of inertia
 Greater mass = greater inertia
 Implications for sport movement
 Decreased mass USUALLY means
you are easier to move (less inertia)
 Agonist/antagonist reciprocal inhibition

62. Law of Acceleration
(Newton’s Second Law)
 “The acceleration of an object is directly
proportional to the force causing it, is in the same
direction as the force, and is inversely
proportional to the mass of the object”
 F = ma

63. Law of Acceleration
(Newton’s Second Law)
 Implications for sport movement
 Club/racket/bat weight
 Follow through
 Athlete body weight

64. Law of Reaction
(Newton’s Third Law)
 “For every action there is
an equal and opposite
reaction”
 Ground reaction force
 Implications for sport
movement
 Artificial turf

65. Equilibrium, Balance &
Stability
 Equilibrium is the state of zero
acceleration (static or dynamic) where
there is no change in the speed or
direction of the body
 Balance is the ability to control
equilibrium, either static or dynamic
 center of gravity
base of support
 point at which all of body's mass &
weight are equally balanced or equally
distributed in all directions
 Stability is a resistance to the
disturbance of equilibrium

66. Center of gravity
 The whole weight of the body, or body segment
(such as the forearm), acts vertically downwards
through the center of gravity of the body or
body segment

69. Factors Influencing Balance
1. Location of the center of gravity in
relation to the base of support
2. Size of the base of support
3. Mass of the person
4. Height of the center of gravity
5. Traction/friction
6. Sensory perceptions

70. Aj.Sirinart Laibsirinon
gan7677@yahoo.com