1. Introduction
1.1 What is discus throw?
The discus throw is an event in track and field athletics competition, in which an athlete
throws a heavy disc — called a discus — in an attempt to mark a farther distance than his
or her competitors.
1.2 What is a discus like?
The discus, the object to be thrown, is a heavy lenticular disc with a weight of 2
kilograms and diameter of 220 mm (8.66 inches) for the men's event, and a weight of 1
kg and diameter of 181 mm (7.17 inches) for the women's event. The discus usually has
sides made of rubber, plastic, wood, or metal with a metal rim and a metal core to attain
the weight.
1.3 How to make a throw?
To make a throw, the competitor starts in a slightly recessed concrete-surfaced circle of
2.5 meters diameter. The thrower typically takes an initial stance facing away from the
direction of the throw. He then spins counter-clockwise (for right-handers) around one
and a half times through the circle to build momentum, then releases his throw.
1.4 How to measure the results?
The discus must land within a 34.92-degree arc marked by lines on the landing zone, and
the competitor must not exit the circle until the discus has landed, then must wait for the
judge to give clearance to exit the ring from the rear half. The distance from the front
edge of the circle to where the discus has landed is measured, and distances are rounded
down to the nearest centimeter or half-inch. The competitor's best throw from the
allocated number of throws, typically three to six, is recorded, and the competitor who
legally throws the discus the farthest is declared the winner.
2. Physics in the discus throw
2.1 Make a guess
Before we search in the physics elements that can affect the result of a discus throw, we
first make a guess of them.
2.1.1 Initial speed
If we want to throw an object farther, we must offer it a bigger force and make it travel as
fast as possible. So we think the initial speed is one physics element.
2.1.2 Gravity
As we know the heavier an object is, the greater inertia the object has. Greater gravity
cause greater inertia and make it more difficult to change it state of motion. So we think
gravity of the discus is another physics element.
2.1.3 Flying direction
If we throw something away, we should choose a direction which means the launch angle.
We did a simple experiment on it. We used a toy gun with same rubber bullets and
changed this shooting direction to shoot at the same height. Then we measure the travel
distance and took done the measurement respectively.
Launch
Travel
Travel
Travel
Travel
Angle(degree) distance 1
distance 2
distance 3
distance(average)
0
0.85m
0.94m
0.78m
0.86m
30
1.57m
1.43m
1.67m
1.58m
60
1.04m
0.98m
1.11m
1.04m
90
0.13m
0.15m
0.11m
0.13m
So we get that the flying direction is also a physic element that influences the throwing
result.
2.1.4 Touching face
Because this sports game is an outdoor game so we must consider the air friction. And
also the discus is not a ball so the touching face with the wind is not always the same.
And the different air friction will influence the flying discus in different extent. So we
think the touching face should be included in the physics elements in the discus throw.
2.2 Do an online research
Later we search the Internet and books for more accurate and precise calculation in the
discus throw. We find the following formulas
T = (V sin(a) + sqrt(V2sin2(a) + 2gh) )/G
d = V cos(a) T - DT2/2
V is the initial speed
a is the launch angle
h the launch height
G = g - L the effective vertical force with g the gravitational force
L the vertical lift force and D the horizontal drag force.
The maximal lift coefficient at 30 degrees of angle of attack is about 1.0 with lift/drag
ratio is about 3.
Typical values are V = 20 m/s, a = 35 degrees, h=1.5 m, G = 0.8g which gives T is about
4 s and d is about 80 m
The two formulas above further improve that our guess is correct.
3. Human physique to enhance the performance in the discus throws
3.1 Arms
Because the athletes have to throw the discus as far as possible, so the arm strength is
necessary. Strong arms can offer more energy and give greater force to the discus so that
the discus will have a greater initial speed. Thus the athletes should have stronger arms to
enhance their performance.
3.2 Waist, Belly, Chest and Back
In the discus throw, athletes have to spin around (counter-clockwise or clockwise) for one
and a half times through the circle to build momentum, then release their throw. The oneand-a-half-round spin will help to give a greater initial speed to the discus. To make a
powerful spin, strong waist, belly, chest and back are necessary. So every athlete must
exercise their muscle on these for parts so that they can make more powerful spins.
3.3 Legs
When athletes spin and throw away the discus, they give the discus a great force but at
the same time, the discus will give a same force to athletes. Therefore, the greater the
force that athletes give to the discus, the greater the force that athletes have to accept.
So athletes need a greater force given from the ground to support them. Strong legs are
necessary at this time to support the athletes.
4. The Training Enhancement
4.1 Overall Core Control
The discus thrower must possess postural, or core, strength: the ability to control his torso
from the kneecaps up to the chest. An athlete with poor core strength will be unable to
affect a good power base, causing him to bend over in the middle of the ring and thrust
his left leg into the bucket and shift his hips onto his support leg. Maintaining an upright
position with the torso will enable the athlete to move fast out of the back of the ring and
maintain balance. Poor core control will also cause him to pause in the middle of the ring
and produce a winding-up effect in the power position - taking away from the speed built
up by the spin. Coaches must understand what the core is or is not doing to keep the
athlete on track with the established model (throwing style). Core control is thus crucial
in ensuring a good power position. The thrower must be able to control his weight
effectively and keep his midsection tight, or firm. The abdominals must be worked on
daily through exercises such as crunches (modified sit-ups), medicine-ball throws, and
twisting exercises.
4.2 Understanding the form and the skill
Various styles are used in modern throwing, with much of the coaching literature
emphasizing the delivery phase. Though the early part of the throw is thought of as mere
preparation for the all-important delivery phase, most young throwers have problems in
the starting position in back of the ring.
This is often the most ignored part of the throw. The emphasis has to be on achieving a
solid power position and a dynamic delivery. The successful beginner will manage to do
this with a slow to moderate start. As these throwers advance, they may turn to a more
aggressive or dynamic start.
The key to a successful throw, no matter what style is used, is balance. At South Carolina,
we teach balance through drills that help internalize the proper feelings. We believe that
the coach must establish the position of strength for each athlete, never copying from a
current champion.
What may be an optimum position for an athlete with the physical attributes of a
champion may be totally unsuitable for a less-endowed, less intensely trained individual.
The prevailing techniques in the discus range from the wide sweeping leg (Wilkins) or
the tight right (Powell). Several of the more accomplished throwers start fast, others start
slow. Some throwers reverse, others do not. Many combine some aspect of both styles.
The coach must select the technique that best fits his athlete.
Coaches working with beginners should pay special attention to the development of the
right reflexes, as it is the coordination and synchronization of the muscular contraction
that produces maximum efficiency.
Coaches who teach a speed technique should make the athlete understand the need for an
aggressive start and an aggressive sweeping right leg. If they teach a power technique,
they should be more concerned with the blocking action in the power position of the no
reverse throw. The athletes should be closely checked for poor reflexive action to avoid
having it become habit forming. Poor habits are difficult to correct.
During the initial stage, coaches should discourage the thrower from being distanceconscious. They should condition their athletes to concentrate on the development of the
right movements in order to establish the right reflexes.
After establishing a proper technique and drilling on the proper reflexes, the coach will
then be called upon to detect and correct faults in the performance.
Every specific form will break down at some point, usually because of the athlete's
unfamiliarity with the pattern or the stress of a big meet or the onset of fatigue. It isn't
that difficult for the experienced eye to detect a gross fault. It is much more difficult to
determine the cause of the fault.
The coach may spot the athlete putting his left foot into the bucket. But to be of
assistance to the athlete, he must be able to identify the cause.
In making the correction, the coach should be positive. Telling an athlete he is "too
slow" conjures up a negative image to the athlete. He may be going as fast as he can. The
coach must then come up with a way to speed up the athlete, either by improving his
physical coordination or by making a technical adjustment.
5. Diet
A high carbohydrate diet (60-70% of the daily caloric intake) is needed to cope with the
training load; breads, pasta and rice-based dishes are ideal for meeting a high
carbohydrate intake (sauces and spreads must be low in fat!). A normal intake of protein
(15-20%) and fat (15-20%) is desirable for all athletes - including discus throwers.
Excessive protein intake is not productive. Discus throwers are not at risk of 'glycogen
depletion' or 'hitting the wall' and an extremely high carbohydrate meal before
competition is not necessary. However, if a thrower has to compete over several hours,
then carbohydrate intake should be high during the day of competition. Bananas,
sandwiches, 'energy bars' etc. would be appropriate foods.
During the course of extended competition, fluid will inevitably be lost; throwers could
benefit from drinking a weakly sugared water solution during the day (ask your
Pharmacist for advice on suitable commercially available products).
6. Physical Aids
1. The discus shoes
A pair of excellent shoes can provide a great support to the thrower. For example, the
shoes can provide strong friction towards the ground. Due to the Newton’s third law, the
support force is provided to the thrower, and therefore a pair of good discus shoes can
help the thrower to achieve a better result.
2. A discus of good quality
It can be easier to throw and therefore the athlete can achieve a better result.
7. Estimation of the total cost
Facilities:
Item
A Discus
10 discuses used in training
Discus Shoes
3 discus shoes used in training
Training Programs:
Estimation of cost /Singapore Dollar
3
30
200
600
Item
A professional coach
3-months fee of coach
Estimation of cost
2000/month
6000
8. Reference
1. Baidu, (2010) Baike June 21, 2010
http://baike.baidu.com/view/68857.htm?fr=ala0_1_1 jiegeng512 、lemon0210 、百科
ROBOT 、守住那一片阳光 、yangxinyi84120 、水上渔家
2. Baidu, (2010) Zhi Dao June 21, 2010
http://zhidao.baidu.com/question/24533338.html?fr=qrl&cid=127&index=3&fr2=query
3. Baidu, (2010) Zhi Dao June 21, 2010
http://zhidao.baidu.com/question/113334029.html
4. Larry. J (1996) Coach and Athletic Director, June 21, 2010
http://findarticles.com/p/articles/mi_m0FIH/is_n8_v65/ai_n18606916/
5. Wikipedia, the free encyclopedia. (2010) Discus Throw, June 21, 2010
http://en.wikipedia.org/wiki/Discus_throw