Trampolines are generally built in four shapes: rectangle, circular, octagon and square. The safest style is the rectangle and the least safe is the circular for reasons which are discussed below.

The rectangle shape is used in competition mainly because it is the safest design. The is due to physics involved in the design. In the rectangle trampoline, the springs criss-cross each other which ensures that the bounce is more controlled and even. Also, the springs at the center of the trampoline stretch more than the springs at the ends. Even if the jumper moves a little to the center of the mat, he will not get thrown off as
easily, as he might with another style of trampoline (i.e. circular, square, octagon). Probably the only downside to the rectangle design is that it is
more expensive to construct and, therefore, more expensive to buy. This is because the materials of the frame and mat must be stronger than those of other types of trampolines because the stress is concentrated at the center portion of the rails. However, as a result of the stronger materials used in constructing this style of trampoline, it will outlast the other styles.

For recreational purposes, the octagon, square and circular trampolines may be purchased. But keep in mind that the least safest design is the circular
trampoline.

Circular (Round) Trampolines: The reason that the circular design is the least safe of the trampolines is because of the physics involved in the design. The springs point towards the center and causes the center of the trampoline to be soft. As a result, you could be thrown off balance if you move away from the center. This would be exacerbated if more than one person
is jumping on the trampoline. More than one person jumping on a trampoline has even been compared to jumping down a funnel because you will "go down
the spout." Do not let anyone tell you that round trampolines are safer because they keep kids in the center.

There is also the increased risk of a collision when two or more people are jumping on a trampoline (of course, that can be true with any shape of trampoline).

Probably the only advantage of round trampolines is that they are cheaper. They cost less to construct because a lighter (and therefore, less costly) frame can be used to construct it because the stress on the frame is distributed equally).

Octagon and 12-sided Trampolines: These are much safer than the round trampolines. One reason for that is because the springs counterbalance the center. This is because there are eight straight rails and the springs end up criss-crossing each other to some extent. The springs in the middle of the rails stretch further than the springs towards the end, thus producing a softer and more stable bounce. There is also more vertical movement on the mat because of the eight straight sides. These mechanisms allow for less pressure behind the bouncer and as a result, the bouncer is less likely to be thrown forward off balance or into another bouncer.

Square Trampolines: There is not as much vertical movement on the mat, as in a rectangle trampoline, but the springs do criss-cross nearly the same way as on a rectangle trampoline. Although there is a more severe bounce with a square trampoline than with a rectangle because there is a greater distance from the springs. This makes the bounce similar to that of a (less safe)
round design because the person is further from the springs making for less travel on the mat.