biomechanics in sports

1. BIOMECHANICS IN SPORTS
BIOMECHANICAL
FOUNDATIONS

2. OBJECTIVES
• Describe human movements using appropriate
anatomical and mechanical terminology,
• Apply mechanical concepts to human movement
problems
• Understand the factors contributing to human
strength and power,
• Determine the muscle actions involved in
movement tasks, and
• Analyze biomechanical aspects of resistance
exercises.

3. 1.INTRODUCTION
Functional anatomy:
• The study of how body systems cooperate to
perform certain tasks.
• To design effective exercise interventions, it is
necessary to know which muscles are active
during which activities and match them with the
appropriate exercises.

4. EXAMPLE
• The quadriceps muscle group is anatomically
defined as a knee extensor. However, these
muscles actually control movement during the
eccentric or “down” phase of the squat—even
though the knee is flexing.

5. BIOMECHANICS:
• A field of study that applies mechanical
principles to understand the function of living
organisms and systems. With respect to human
movement, several areas of biomechanics are
relevant, including movement mechanics, fluid
mechanics, and joint mechanics.

6. 2.TERMINOMLOGY AND PRINCIPLES
Mechanically speaking, there are two basic types
of movement:
• Linear motion, in which a body moves in a
straight line (rectilinear motion) or along a
curved path (curvilinear motion)
• Angular motion (also rotational motion) in
which a body rotates about a fixed line known as
the axis of rotation(also fulcrum or pivot)
• General motion involve a combination of
linear and angular motion.

7. 2.1.PLANES AND AXES

8. Sagittal plane
• dividing the body into left and right halves
• median plane refers to the midline
• flexion and extension of the hip occurs in the sagittal
plane
Frontal plane
• dividing the body into anterior and posterior halves
• abduction and adduction of the shoulder occurs in
the coronal plane
Tranverse/axial plane (plan tranversal)
• dividing the body into superior and inferior halves
• Left and right movement of the head

9. Think of an axis as a metal pole and the joint is rotating around that pole
Sagittal axis
• passes horizontally from anterior to posterior.
• formed by the intersection of the sagittal and transverse plane.
• abduction and adduction of the shoulder occurs around the sagittal axis
Frontal axis
• passes horizontally from left to right
• formed by the intersection of the coronal and transverse plane
• flexion an extension of the hip occurs around the coronal axis
Vertical axis
• passes vertically from superior to inferior
• formed by the sagittal and frontal planes

10. 2.2. MAJOR JOINT MOVEMENTS
Major joint movements occurs within the three
planes of motion and around the three axes.

11. Wrist—sagittal
• Flexion
• Exercise: wrist curl
• Sport: basketball free
throw
• Extension
• Exercise: wrist extension
Sport: racquetball
backhand
• Wrist—frontal
• Ulnar deviation
• Exercise: specific wrist curl
Sport: baseball bat swing
• Radial deviation
• Exercise: specific wrist curl
Sport: golf backswing

12. Shoulder—sagittal
Flexion
Exercise: front shoulder raise
Sport: boxing uppercut punch
Extension
Exercise: neutral-grip seated row
Sport: freestyle swimming
stroke
Shoulder—frontal
Adduction
Exercise: wide-grip lat
pulldown Sport: swimming
breast stroke
Abduction
Exercise: wide-grip shoulder
press
Sport: springboard diving

13. • Shoulder—transverse
• Internal rotation
• Exercise: arm wrestle move-
ment (with dumbbell or cable)
Sport: baseball pitch
• External rotation Exercise:
reverse arm wrestle movement
Sport: karate block
• Shoulder—transverse
(upper arm to 90° to trunk)
Horizontal adduction
Exercise: dumbbell chest fly
Sport: tennis forehand
• Horizontal abduction
Exercise: bent-over lateral
raise
• Sport: tennis backhand

14. • Neck—sagittal
• Flexion
• Exercise: neck machine Sport:
somersault
• Extension Exercise: dynamic
back bridge Sport: back flip
• Neck—transverse
• Left rotation
• Exercise: manual resistance
Sport: wrestling movement
• Right rotation
• Exercise: manual resistance
Sport: wrestling movement

15. • Neck—frontal
• Left lateral flexion Exercise:
neck machine Sport: slalom
skiing
• Right lateral flexion Exercise:
neck machine Sport: slalom
skiing
• Elbow—sagittal
• Flexion
• Exercise: biceps curl Sport:
bowling
• Extension
• Exercise: triceps pushdown
Sport: shot put

16. • Trunk—sagittal
Flexion Exercise: sit-up
• Sport: javelin throw
follow-through
• Extension
• Exercise: stiff-leg
deadlift Sport: back flip
• Trunk—frontal
• Left lateral flexion Exercise:
medicine ball overhead hook
throw
• Sport: gymnastics side aerial
• Right lateral flexion
• Exercise: side bend
• Sport: basketball hook shot

17. • Trunk—transverse
• Left rotation
• Exercise: medicine ball side
toss
• Sport: baseball batting
• Hip—sagittal
• Flexion
• Exercise: leg raise
• Sport: American football punt
•
• Extension
• Exercise: back squat Sport:
long jump take-off

18. • Hip—frontal Adduction
Exercise: standing adduction
machine
• Sport: soccer side step
•
• Abduction Exercise: standing
abduction machine Sport:
rollerblading
• Hip—transverse
• Internal rotation
• Exercise: resisted internal
rotation Sport: basketball pivot
movement
• External rotation
• Exercise: resisted external
rotation Sport: figure skating
turn

19. • Hip—transverse
• (upper leg to 90° to trunk)
Horizontal adduction
Exercise: adduction machine
Sport: karate in-sweep
• Horizontal abduction
Exercise: seated abduction
machine
• Sport: wrestling escape
• Knee—sagittal
• Flexion
• Exercise: leg (knee) curl Sport:
diving tuck
• Extension
• Exercise: leg (knee) extension
Sport: volleyball block

20. • Ankle—sagittal Dorsiflexion
Exercise: toe raise Sport:
running
• Plantar flexion
• Exercise: calf (heel) raise
Sport: high jump
• Ankle (subtalar)—frontal
• Inversion
• Exercise: resisted inversion
Sport: soccer dribbling
• Eversion
• Exercise: resisted eversion
Sport: speed skating

21. 3.KINETICS AND KINEMATICS
• The study of movements from a descriptive perspective
without regard to the underlying forces is called
kinematics. Kinematic assessments includes:
1. Timing: the athlete took 0.8 s to lift the barbell
2. Position or location: client held his arm at 90° of
abduction
3. Displacement: a trainee moved his elbow through
60° of flexion
4. Velocity in m/s: a volleyball player extended
his or her knee at 600º/s while jumping
5. Acceleration in m/s²: gravity accelerated a
jumper’s body toward the ground at 9.81 m/s2

22. • Kinectics :
• movement assessment with respect to the forces
involved. Human movement happens as a result
of mechanical factors that produce and control
movement from the inside (internal forces such
as muscle forces) or affect the body from the
outside (external forces such as gravity)

23. 4.FORCE(NEWTON)
• Force, a fundamental element in human
movement mechanics, is defined as a
mechanical action or effect applied to a body
that tends to produce acceleration.
• 1KG=9.81 N

24. • In order to complete the vertical
jump test the athlete will first
load the legs by squatting down
allowing gravity to push the
athlete towards the ground.
• The athlete will then contract the
muscles in their legs and glutes
in order to push down into the
ground and also contract their
arm muscles to swing their arms
vertically into the air.
• Gravity and the lower body
muscle contractions create a
force in the downward direction
into the ground. This force is
then met by an equal and
opposite reaction force that
propels the athlete into the air.

25. • There are seven force-related factors:
• Magnitude (how much force is produced or
applied)
• Location (where on a body or structure the force is
applied)
• Direction (where the force is directed)
• Duration (during a single force application, how
long the force is applied)
• Frequency (how many times the force is applied in
a given time period)
• Variability (if the magnitude of the force is
constant or changing over the application period)
• Rate (how quickly the force is produced or applied)

26. 5.NEWTON’S LAWS OF MOTION
• Mechanical analysis of human movement is
based largely on the work of Sir Isaac Newton
(1642-1727)
• Newton’s laws of motion are as follows:
First law of motion= INERTIA: A body at rest
or in motion tends to remain at rest or in
motion unless acted upon by an outside force.

27. • Inertia is the object’s or body’s resistance to
change. It is also the basic law for static
equilibrium.
• The first law of motion essentially dictates that
forces are required to start, stop, or modify body
movements.
• When a jumper leaves the ground, for example, a
force (gravity) acts to slow the upward movement
until the jumper reaches his or her peak, and then
continues to act in accelerating the jumper’s body
toward the ground for landing.

28. Second law of motion (ACCELERATION)
• A net force F should act on a body to produce
acceleration
• (a) proportional to the force according to the equation
• F = m . a (where m = mass).
• In other words, force equals mass times acceleration.

29. • Newton’s second law of motion is seen in a lift-
ing task (e.g., deadlift).
• The individual must exert enough force to
overcome the force of gravity and accelerate the
barbell upward.
• The equation F = m .a can be used to
determine the magnitude of bar acceleration.
• A greater force (F) will produce a proportionally
greater acceleration (a).

30. Third law of motion(ACTION/REACTION)
• For every action there is an equal and opposite
reaction.
• Newton’s third law of motion says that every force
produces an equal and opposite reaction force.
• In running, for example, at each foot contact, the
foot exerts a force on the ground.
• The ground equally and oppositely reacts against the
runner’s foot to produce what is termed a ground
reaction force.
• The magnitude and direction of the ground
reaction force determine the runner’s acceleration.

32. 6.MOMENTUM
• Momentum can be defined as "mass in motion."
All objects have mass; so if an object is moving,
then it has momentum - it has its mass in
motion. The amount of momentum that an
object has is dependent upon two variables: how
much stuff is moving and how fast the stuff is
moving.
• Momentum = mass • velocity

33. The units for momentum would be mass units times velocity units. The
standard metric unit of momentum is the kg•m/s

34. ANGULAR MOMENTUM
• angular momentum is the product of moment of
inertia (I) and angular velocity , where I is the
resistance to a change in a body’s state of angular
motion.
• moment of inertia=
body mass X distance from axis of rotation
• If the mass is close to the axis of rotation= decrease
in moment of inertia=increased angular velocity
• If the mass is far from axis of rotation= increase in
moment of inertia=decreased angular velocity

36. • Transfer of momentum is the mechanism by
which momentum is transferred from one body to
another.
• In a throwing motion, for example, a softball
pitcher transfers momentum sequentially from
the legs and torso to the upper arm, to the
forearm, and eventually to the hand and the ball
at pitch release.
• Another example of momentum transfer can be
seen when someone “cheats” during a maximal
bicep curl exercise.

37. • When performing a biceps curl
one arm at a time, a muscular
imbalance would be hidden by
changing the pace. When
moving together we are forcing
work on both arms equally.
• Control more weight since I
want to prevent the dumbells
momentum by pushing me
backwards. This way I’m
activating my core to prevent
this moment transfer.

38. • To change (either increase or decrease)
momentum, a mechanical impulse must be
applied. Impulse is the product of force (F)
multiplied by time (t). Thus, increasing the
amount of applied force or the time of force
application results in a greater change in
momentum.

39. • Since the mass of the body and velocity are constant, we should an
identical moment.
• In case A, we obtain a large peak force = a higher impulse during a
small time component.
• In case B, we obtain a more controlled peak force by bending the
knees and extending the time component. This will help in preventing
injury.

40. 8.TORQUES
• For angular motion, the mechanical term is torque (T),
or moment of force (M, usually shortened to
“moment”), and is defined as the effect of a force that
tends to cause rotation or twisting about an axis.
• Torques creates an angular acceleration, the same way
force creates a linear acceleration.
• Torque (T) is calculated as the mathematical product of
force (F) times moment arm (d):
• T = F . d
• The moment arm is defined as the perpendicular
distance (d) from the fulcrum (axis) to the line of force
action.

41. A moment arm can be defined as the
"perpendicular distance between the centre
of rotation of an object and the line of
action of a force acting on the object

42. • Because the hips are the main rotation force in the squat the
back must be kept straight to allow the hip dominant-
movement that is involved this means that to make sure the
force of the barbell is placed on the hips, the hip moment arm
is extended and the moment arm of the knees are
shortened (Rippetoe 2015).
• This is because in the squat movement the Gluteal muscles do
more work than the Quadriceps in terms of force production.
This is the most efficient way to squat because if the
quadriceps were the dominant muscle there would be less
gluteal muscles activated and therefore less force production.
An interesting finding in Escamilla et al. (2001) study of the
biomechanical review of varying squat widths have found that
the greater depth of the squat the greater increase in the hip's
moment arm (Escamilla 2001).

43. 9.LEVER SYSTEMS
• A lever is defined as a rigid structure, fixed at a
single point (fulcrum or axis), to which two forces
are applied
• In terms of human movement, the rigid structure is
a bone moving about its axis of rotation. One of the
forces (FA) is commonly termed the applied force
(also effort force) and is produced by active muscle.
• The other force (FR), referred to as the resistance
force (also load), is produced by the weight being
lifted (i.e., gravity) or another external force being
applied (e.g., friction, elastic band).

44. 9.1.MECHANICAL ADVANTAGE
• Mechanical advantage can be expressed
as: Mechanical advantage = effort arm ÷
resistance arm. Therefore, the greater the effort
arm in comparison to the resistance arm, the greater
the mechanical advantage.
• If MA=1 effort=resistance
• If MA>1 less effort is required to move high
resistance
• If MA <1 more effort is required to move small
resistance.

45. 9.2.FIRST CLASS LEVER
• A lever in which the muscle
force and resistance acts on
the opposite sides of the
fulcrum.
• Fulcrum=elbow
• Resistance=weight of the arm
Or weights
• Effort=elbow extension
• MA<1

46. 9.3.SECOND CLASS LEVER
• The muscle force and resistive
force act on the same side of
the fulcrum
• The muscle force acts through
a moment arm longer than the
resistive force.
• Calf muscles work to raise the
body onto the ball of the feet.
• MA>1
• Small muscle force required to
move a high resistance

47. 9.4.THIRD CLASS LEVER
• A lever for which the muscle
force and resistive force act on
the same side of the fulcrum.
• The muscle force acts through
a moment arm shorter than
the resistive force
• Muscle force has to be greater
than the resistive force
• Mechanical disadvantage< 1

48. 10.MECHANICAL WORK
• work (W) is defined as the product of force
times the distance (d) through which an object
moves:
• W = F. d
• The standard unit of work is the joule (1 J = 1
N·m).

49. • For example a body builder during a bench press
exercise acts against a barbell and his arms with
a constant force of 2000 N. The centre of gravity
of the barbell – arms system is vertically
displaced by 0,6 m. The work performed by the
body builder is 1200 N/m or J
• The work value could be negative when the body
is displaced against the direction of force.

51. • Muscles can also perform mechanical work.
• When muscles contract, they produce tractive
forces that act on muscles’ insertions.
• Muscle contractions are divided into:
• Concentric contraction – „the force generated
is sufficient to overcome the resistance, and the
muscle shortens as it contracts“ (Knuttgen
a Kraemer, 1987).
• Muscles then perform positive mechanical work
because muscle force acts along the line of
muscles’ insertions. The muscle shortens.
• Energy is generated by the muscle and transferred
to the segment.

52. • Eccentric contraction – „the force generated is
insufficient to overcome the external load on the
muscle and the muscle fibres lengthen as they
contract“ (Knuttgen a Kraemer, 1987). Muscles then
perform negative mechanical work because muscle
force acts against the direction of the motion of
muscles’ insertions. The muscle lengthens.
• Isometric contraction – „the muscle remains the
same length“ (Knuttgen a Kraemer, 1987). There is
no displacement of muscles’ insertions in relation to
each other, therefore no work is performed.

54. 11.POWER
power (P), is calculated as the amount of work
(W) divided by the time (t) needed to do the
work:
• P = W / t
• The standard unit of power is the watt (1 W = 1
J/s).
• In the bench press example, the up phase of the
first rep would have a power of 400 W (400 J / 1
s), while the last rep would have a lower power
of 200 W (400 J / 2 s)

55. • Many high-speed movement tasks (e.g., jumping,
throwing) require high power output. To produce
powerful movements and to train for power, a person
must generate high forces while moving at a high rate
of speed (i.e., high velocity)
• The three events in powerlifting competitions are the
squat, bench press, and deadlift.
• At maximal levels, none of these lifts is performed
quickly.
• Thus, while tremendous strength certainly is required
for powerlifting success, the power output is two to
three times lower than for the Olympic lifts

56. 12.ENERGY
• Mechanical energy is defined as the ability, or
capacity, to perform mechanical work.
• Mechanical energy can be classified as either
kinetic energy (energy of motion) or potential
energy (energy of position or deformation).

57. • Kinetic energy is directly proportional to the
square of the body’s velocity.
• where Ek is kinetic energy (J), m is mass (kg),
and v is velocity (m/s).
• For example, a runner who speeds up from 5
m/s to 6 m/s (a 20% increase) would increase
his or her linear kinetic energy by 44%.
• KINETIC ENERGY

58. Potential energy
Gravitational Elastic
• Gravitational potential
energy is ability of a body to
perform work due to its
position in the Earth’s
gravitational field.
• where Ep is potential energy
(J), m is mass (kg), g is
gravitational acceleration (9,81
m/s2) and h is height (m).
• PE = m . g .h
• Elastic energy is an ability of
a body to perform work due to
its being deformed. (stretched,
compressed, bent, twisted)
• For example you can store
elastic potential energy in
your Achilles tendon when
you squat down before
jumping, then release that
energy during the launch
phase of a jump