Trampoline

Trampoline is a device consisting of a piece of taut, strong fabric stretched over a steel frame using many coiled springs. People bounce on trampolines for recreational and competitive purposes.

The fabric on which users bounce (commonly known as the 'bounce mat' or 'trampoline bed') is not elastic in itself; the elasticity is provided by the springs that connect it to the frame.

The first modern trampolines

The first modern trampoline was built by George Nissen and Larry Griswold in 1936.  Nissen was a gymnastics and diving competitor and Griswold was a tumbler on the gymnastics team, both at the University of Iowa, USA. They had observed trapeze artists using a tight net to add entertainment value to their performance and experimented by stretching a piece of canvas, in which they had inserted grommets along each side, to an angle iron frame by means of coiled springs. It was initially used to train tumblers but soon became popular in its own right. Nissen explained that the name came from the Spanish trampolín, meaning a diving board. George Nissen heard the word on a demonstration tour in Mexico in the late 1930s and decided to use an anglicized form as the trademark for the apparatus.

In 1942 Griswold and Nissen created the Griswold-Nissen Trampoline & Tumbling Company, and began making trampolines commercially in Cedar Rapids, Iowa.

The generic term for the trademarked trampoline was a rebound tumbler and the sport began as rebound tumbling. It has since lost its trademark and has become a generic trademark.

Use in flight and astronaut training

During World War II, the United States Navy Flight School developed the use of the trampoline in its training of pilots and navigators, giving them concentrated practice in spatial orientation that had not been possible before. After the war, the development of the space flight programme again brought the trampoline into use to help train both American and Soviet astronauts, giving them experience of variable body positions in flight.

Cross-training for other sports

There are a number of other sports that use trampolines to help develop and hone acrobatic skills in training before they are used in the actual sporting venue. Examples can be found in diving, gymnastics and freestyle skiing.

Construction

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 4.28 by 2.4 metres (14 ft 0.5 in × 7 ft 10 in) in size fitted into the 5.2 by 3.05 metres (17 × 10 ft) 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 weaker. 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 Springfree trampoline design allows the steel jumping frame to be placed below the jumping plane, ostensibly improving the user's safety.

Safety

Using a trampoline can be dangerous, and in organized clubs and gyms there are usually large safety end-decks with foam pads at each end and spotters placed alongside the trampoline to try to break the fall of any athlete who loses control and falls. The majority of injuries happen on privately owned home trampolines. Bouncing off a trampoline can result in a fall of 3–4 metres (10–13 ft) from the peak of a bounce to the ground or a fall into the suspension springs and frame. There has been an increase in the number of home trampolines in recent years and a corresponding increase in the number of injuries reported, leading some medical organizations to suggest that they be banned.

Authorities recommend that only one person should be allowed to jump at a time to avoid collisions and people being catapulted in an unexpected direction or higher than they expect. In fact, one of the most common sources of injury is when there are multiple users bouncing on the trampoline at one time. More often than not, this situation leads to users bouncing into one another and thus becoming injured; many suffer broken bones as a result of landing strangely after knocking into another user.

Another of the most common sources of serious injury is an attempt to perform somersaults without proper training. In some cases, people land on their neck or head, which can cause paralysis or even death. A famous incident in the 1960s paralyzed pole-vaulting champion Brian Sternberg from the neck down.

History

A kind of trampolining was done by the Inuit, who would toss each other into the air on a walrus skin (see Nalukataq), something like the sheet used by firemen to catch people jumping out of burning buildings. There also is some evidence of people in Europe having been tossed into the air by a number of people holding a blanket; Mak in the Wakefield Second Shepherds' Play and Sancho Panza in Don Quixote are both subjected to blanketing – however, these are clearly non-voluntary, non-recreational instances of quasi-judicial, mob-administered punishment. The 19th-century poster for Pablo Fanque's Circus Royal, on which The Beatles' song "Being for the Benefit of Mr. Kite!" is based, references performance on trampoline, though the device is thought to have been something more like a springboard than the fabric-and-coiled-springs apparatus presently in use.

These may not be the true antecedents of the modern sport of trampolining, but in the early years of the 20th century, some acrobats used a "bouncing bed" on the stage to amuse audiences. The bouncing bed was, in reality, a form of small trampoline covered by bedclothes, on which acrobats performed mostly comedy routines.

According to circus folklore, the trampoline was supposedly first developed by an artiste named du Trampolin, who saw the possibility of using the trapeze safety net as a form of propulsion and landing device and experimented with different systems of suspension, eventually reducing the net to a practical size for separate performance. While there were trampoline-like devices used for shows and in the circus, the story of du Trampolin is probably apocryphal, and no documentary evidence has been found to support it.

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.