Throwing a discus is unlike most other throws, in that the majority of the speed imparted to the discus comes from rotating your body, not from actually 'throwing'. In order to throw a discus well, you need to learn how to rotate very fast, and let go of the discus at just the right instant. Let's look at how much speed is involved. For simplicity, let's assume you can rotate your body with your arm out (holding the discus) in a circle that's 1.8 metres wide. The total distance covered by the discus during your final rotation will be the circumference of this circle, or 5.65 metres, as worked out on the right. Let's assume you can make that last rotation in a time of just one second. This means the discus will travel 5.65 m in one second. Its speed  v  will be 5.65 m/s, as worked out on the right.   This is the speed at which the discus will leave your hand, if you let go at just the right instant. It is quite substantial ... You need to let go when your arm is at a right angle to the direction in which you want the discus to travel. A good discus thrower with a strong arm can also use that arm as a whip, to apply some more speed to the discus as it leaves his hand. But this speed won't be near as large as the speed of rotation, which is over 20 km/h ...   To improve your discus throwing, you need to stretch out as you rotate, so your circle is larger. At the same time, you need to increase your speed as much as you can. Increasing your speed of rotation is the most important thing you can do to improve your result. Finally, a good muscular arm helps, so you can add a final bit of speed with a 'whip' of your arm. Resources