There are two generic types of trampoline, competitive and recreational
Competitive
The frame of a competitive trampoline is made of steel and can be made to fold up for transportation to competition venues. The trampoline bed is rectangular 428 cm (approx. 14 feet) by 214 cm (approx. 7 feet) in size fitted into the 520 cm x 305 cm (17′ x 10′) frame with around 110 steel springs (the actual number may vary by manufacturer). The bed is made of a strong fabric, although this is not itself elastic; the elasticity is provided only by the springs. The fabric can be woven from webbing, which is the most commonly used material. However, in the 2007 World Championships held in Quebec City, a Ross (or “Two-String”) bed, woven from individual thin strings, was used. This type of bed gives a little extra height to the rebound.
Recreational
Recreational trampolines are less sturdily constructed than competitive ones and their springs are less strong. They may be of various shapes, though most are circular, octagonal or rectangular. The fabric is usually a waterproof canvas or woven polypropylene material.
As with competitive trampolines, recreational trampolines are usually made using coiled steel springs to provide the rebounding force. New Zealander Dr. Keith Vivian Alexander of the University of Canterbury designed a trampoline that replaces the springs with cantilevered pultruded fibreglass rods to provide the rebounding force. This spring-free design allows the steel jumping frame to be placed below the jumping plane, ostensibly improving the user’s safety.
Mini-trampolines
A mini-trampoline (also known as a trampette, jogging trampoline or exercise trampoline) is a trampoline less than one metre in diameter and about a foot off the ground, often kept indoors and used as part of a physical fitness regime. So-called rebounding provides a form of exercise with a low impact on knees and joints. Mini-trampolines do not give a rebound as high as larger recreational or competitive trampolines.
Educational use
In co-operation with the University of Bremen and the German Aerospace Center (DLR), the machtWissen.de Corporation from Bremen, Germany developed the weightlessness demonstrator “Gravity Jumper” based on a trampoline. Due to the acceleration during the jump, an acceleration force takes effect in addition to the usual gravitational force. Both forces add up and the person on the trampoline seems to become heavier. As soon as the jumper leaves the trampoline, he is under a free fall condition. Physically speaking, gravitation and inert force compensate completely, which means that the jumper is weightless. Every person receives a three-axis acceleration sensor, fastened to them with a belt. The sensor transmits the data of the flight path to a monitor; a monitor shows the course of the acceleration, including the zero gravity phase. The interplay of acceleration and microgravity becomes apparent.