Throwing the Discus
1. Construction. The body of the discus may be solid or hollow and shall be made of wood, or other suitable material, with a metal rim,
the edge of which shall be circular. The cross section of the edge shall be rounded in a true circle having a radius of approximately
6mm. There may be circular plates set flush into the centre of the sides. Alternatively, the discus may be made without metal plates,
provided that the equivalent area is flat and the measurements and total weight of the implement correspond to the specifications.
Each side of the discus shall be identical and shall be made without indentations, projections or sharp edges. The sides shall taper in a
straight line from the beginning of the curve of the rim to a circle of a radius of 25mm to 28.5mm from the centre of the discus.
The profile of the discus shall be designed as follows. From the beginning of the curve of the rim the thickness of the discus
increases regularly up to the maximum thickness D. This maximum value is achieved at a distance of 25 mm to 28.5mm from the axis of
the discus Y. From this point up to the axis Y the thickness of the discus is constant. Upper and lower side of the discus must be
identical, also the discus has to be symmetrical concerning rotation around the axis Y.
The discus, including the surface of the rim shall have no roughness and the finish shall be smooth and uniform throughout.
2. It shall conform to the following specifications:
1. All discus throws shall be made from an enclosure or cage to ensure the safety of spectators, officials and competitors. The cage
specified in this Rule is intended for use in a major stadium with spectators all the way round the outside of the arena and with other
events taking place in the arena. Where this does not apply, and especially in training areas, a much simpler construction may be
satisfactory. Advice is available, on request, from national organisations or from the IAAF Bureau.
Note: The hammer cage specification may also be used for discus throwing, either by installing 2.135/2.50m concentric circles,
or by using an extended version of that cage with a second discus circle installed behind the hammer circle.
2. The cage should be designed, manufactured and maintained so as to be capable of stopping a 2kg discus moving at a speed of up to 25
metres per second. The arrangement should be such that there is no danger of ricocheting or rebounding back towards the athlete or
over the top of the cage. Provided that it satisfies all the requirements of this Rule, any form of cage design and construction
can be used.
3. The cage should be U-shaped in plan. The width of the mouth should be 6m, positioned 5m in front of the
centre of the throwing circle. The height of the netting panels should be at least 4m.
Provision should be made in the design and construction of the cage to prevent a discus forcing its way through any joints in the cage or
the netting or underneath the netting panels.
4. The netting for the cage can be made from suitable natural or synthetic fibre cord or, alternatively, from mild or high tensile steel
wire. The maximum mesh size shall be 50 mm for steel wire and 44 mm for cord netting. The minimum size of cord or wire depends
on the construction of the cage, but the minimum breaking strength should be 40kg.
In order to ensure the continued safety of the cage, the steel netting should be inspected at least every 12 months.
Visual inspection is not sufficient for fibre cord. Instead, several sample lengths of the standard cord should be worked into the
netting by the manufacturer. One of these can be removed every 12 months and tested to ensure the continued strength of the netting.
5. The maximum danger sector for discus throws from this cage is approximately 98°, when used by both right and left handed
throwers in the same competition. The position and alignment of the cage in the arena is, therefore, critical for its safe use.