MOTION ANALYSIS
BY
DR. AJAY KUMAR
READER
SCHOOL OF PHYSICAL EDU.
STEPS OF ANALYSIS
Name of the skill
Brief description of the skill
The specific objective of the motor
skill
Identification of major and secondary
categories
STEPS OF ANALYSIS (cont)
The objectives of analysis i.e.
mechanical, anatomical or both
Identification of principles
Application of principles in motor
skills
Analysis of Walking
Name of the skill:
Discus Throw
Description of Skill of Discus
Throw
Discus throw technique has evolved
from standing on a sloping platform
to a one and three quarter turn that
is still the technique used today.
Because of its rotational nature, it is
often perceived as a complex event.
The truth is that the discus is not
that complex and can be understood
with a little bit of work to understand
the process of discus throw
development, as well as the science
behind it.
Description of Skill (cont)
When discussing discus throw
technique it is important to make a
clear distinction between two things,
technique and style.
Some coaches use these terms as if
they are the same thing. In reality,
they are very different.
Science tells us that technique is the
mechanical principles that dictate the
movements in an event. Style is the
individual athlete and coach's
interpretation of that model.
In simple terms Physics doesn't
change and we do not coach robots!
So lets make sure as coaches we are
looking at technique not style.
Description of Skill (cont)
While competent athletes will focus
on the entire throw itself, the phases
of the throw are important and need
to be looked at.
For example, imbalances or poor
position at the back of the circle,
could be causing problems of
imbalance and poor right leg action
at the front of the circle.
No matter which discus throw phase
we are in it is important that the
coach understands the process of
fault and correction, and the
biomechanics behind the technical
changes made.
Description of Skill (cont)
While discus drills are useful in
removing technical deficiencies, it is
only by understanding the technique
of the event, that drills can be
applied successfully.
Objective of Motor Skill
The objective of discus throw is to
achieve maximum linear distance by
using a circular momentum produce
through an efficient and dynamically
balanced movement of the body in
side circle.
For achieving this the mechanical
principles relating centripetal and
centrifugal force, projectile,
aerodynamics, and maintaining
dynamic balance should be taken
care of.
Identification of Categories
Primary Category: Giving impetus to
external object.
Secondary Category: Supported by
ground and locomotion on foot.
Objective of Analysis
Mechanical Analysis
Identification of Principles
In all four throwing events the
distance obtained is dependent upon
the releasing speed, releasing angle,
releasing height and aerodynamics
factors.
The principles related to these
factors are important to understand
the mechanical analysis of discus
throw.
Application of Mechanical
Principles
1. Principles related to maintaining
dynamic balance.
2. Principle related to providing
maximum releasing speed.
1. Application of force
2. Angular Momentum
3. Lever (Range of Motion)
3. Principles related to maintaining
correct releasing angle and
aerodynamics.
1. Drag
2. Lift
Application of Mechanical
Principles (cont)
An efficient throwing technique is
one in which the athlete exert the
force of his entire body over the
greatest range possible (force x
distance = work) and therefore for
the longest period of time (force x
time = impulse)
The force must be exerted against
the implement in proper direction as
far as practicable in the direction of
ultimate throw. (As a general rule,
preliminary movement of discus
throwing is more in horizontal
direction and in delivery more lift
than horizontal drive.
These two principles are fundamental
to correct preliminary swing in discus
throw and it needs fast stretching
and powerful recoiling of large
muscle group.
In particular, by driving the pelvis
ahead of the trunk, the good thrower
creates torque between hips and
shoulder
Application of Mechanical
Principles (cont)
Summation of force : The various
forces of the body should be exerted
in definite sequence and proper
timing.
Turn in the discus throw should be so
fast as an athlete can use it for good
purpose but never so fast that he is
unable to exert full body force in the
delivery.
Principles (cont)
For maximum speed of release the
ground must provide adequate
resistance to thrower’s movement
and for as long as he is in contact
with the implement.
Some advance athlete use jump
release throwing and it is a matter of
research.
Principles (cont)
Angle of Release
When points of release and point of
landing are the same height above
the ground (and aerodynamic factors
may be ignored ) the optimum angle
for the projectile of a missile,
regardless of its speed is one i.e. 45
degree.
Principles (cont)
However in all four throwing events
in athletics the implement is thrown
from a point above the ground but
the landing is on the ground i.e.
below the level of release angle, as
well the shape of the implement
differ and it may affects the release
angle.
Principles (cont)
In shot and hammer events (where
aerodynamic factors are of no
account, due to their shape) the
optimum release angle will be near
the 45 degree.
Principles (cont)
In discus throw by the virtue of their
size and shape, aerodynamic forces
also influence the flight as they do
not follow the simple parabolic
curves.
In moving through the air a discus
pushes the air and perform work.
This work needs energy which
reduces the speed of discus.
Principles (cont)
The air resistance depends upon the
shape and size of the discus:
– The thinner and sharper it is in front, the
smaller is the air resistance.
– This can be further reduced if the cross-section
narrows gradually i.e. streamline effect.
If
If the discus is thrown at an angle
the upper side develops irregular air
whirls and under side air passes as
streamlined.
It develops a reduced air pressure on
the above side of discus and an
increased air pressure on under side
of discus.
This air pressure develop a vertical
force i.e. lift and a horizontal force
i.e. drag on discus.
The ratio between lift and drag
depends upon the angle of attack.
END