The modern trampoline was patented by George Nissen in 1936 who championed its use for recreation and competition. During World War II, the trampoline was used to train pilots to improve their spatial orientation and balance, and after the war, it was used in schools and competitively (46).
The development of international competition in trampoline is well summarized by the Federation Internationale de Gymnastique (FIG), which is the ruling body for international trampoline gymnastics. This site also clearly defines the rules of international trampoline competition. The first U.S. National Championships were held in 1948. The Federation Internationale de Trampoline was formed in 1964, and in March of that year, the first world championship was held in London (23). Three forms of competitive gymnastic\ trampolining exist: individual trampoline, synchronized trampoline, and mini-trampoline. Each method will be discussed in greater detail later in this article. The first Olympic competition in trampoline began in 2000; however, Olympic competition only allows individual trampoline competition. International competition includes all three forms of trampolining. Males and females participate in competitive trampolining.
Despite the resurgent popularity of trampolines in the past decade, it has been recognized since the late 1960s that there were significant risks involved with the use of trampolines, including spinal cord injury and paralysis (8,27,39-43). In 1971, the National Collegiate Athletic Association (NCAA) Gymnastics Committee determined that the risks of trampoline competition were unacceptable and removed the event from national competition and training (22); however, in 1978 (reaffirmed in 2002), the NCAA revised this statement, allowing trampoline to be used as a training device under careful supervision (32).
The American Academy of Pediatrics (AAP) published a position statement with regard to trampoline use in 1977 (5). They referred to the National Athletic Injury Reporting System survey, which revealed that spinal cord injury with permanent paralysis occurred more frequently with trampolines than with any other gymnastic activity. They also reported that only football led to more cases of permanent paralysis (5,31). The AAP recommended that trampolines not be used under any circumstance. In 1981, the AAP softened their position and stated that trampolines might be used safely, but only under controlled circumstances. The Academy also called for a careful evaluation of injury incidence and severity with the use of trampolines and outlined very clear guidelines to decrease the risk of injury with the use of trampolines. They maintained their stance and clearly stated that trampolines should not be used in the home environment (4). An additional statement on trampoline use at home was released by the AAP in 1999 in response to the reported 83,400 trampoline injuries that occurred in 1996 (3).
Concern for an increase in trampoline injuries in response to the Olympic Debut of trampolining resulted in a statement from the U.S. Consumer Product Safety Commission (CPSC) in 2000 reporting that, in 1998 alone, an estimated 640,000 "backyard" trampolines were sold in the United States (16). The CPSC also estimated that in 2001, there were 91,870 injuries in the United States and clearly outlined recommendations that might decrease the risk of injury (12). Online search of the CPSC home page using the search term "trampoline" also demonstrates multiple recalls for intrinsic safety issues of specific trampolines and enclosures, with the most recent recall in March 2009 (10). Because of the increased use of trampolines recreationally and the marked increased number of children presenting to emergency department, in 2008 the American Academy of Orthopaedic Surgeons (AAOS) also issued a statement and guidelines with regard to the dangers of unsupervised use of trampolines and tips to mitigate the chances of injury (2).
There is no reported evidence that any of these efforts have led to a decrease in the number or severity of injuries. On the contrary, there are multiple recent reports that injuries with their use is increasing in many parts of the world.
POPULARITY OF TRAMPOLINES
The Chartered Society of Physiotherapy (Physios) in England has stated that trampolines are a "great way to take exercise as long as they are used safely." They also espouse it as a means to improve balance and coordination, boost self esteem and confidence, and also provide a sense of achievement. Physios, however, acknowledges that in 2002 in England alone, 11,500 people required emergency treatment for injuries sustained on the trampolines, an increase of more than 50% in a 5-yr period (40).
Trampoline use has been advocated by some clinicians in the treatment of cystic fibrosis, as an adjunct to physical therapy, to potentially enhance sputum production and cardiopulmonary function, but questions remain with regard to efficacy, as well as safety (6,13). However, the senior author's experience suggests that trampolines will be used by individuals and families with disabilities, regardless of medical recommendations of the risks. Many of these families believe that trampolining is one of the few forms of sport that their child can participate in for pleasure and exercise.
The risks involved in participation in trampoline have been defined clearly and include but are not limited to fractures, sprains or soft tissue injury, head and neck injury, spinal cord injury, and permanent paralysis and death (7,8,16,17,24,25,30,47). In 2000, the CPSC reported 11 deaths over a 10-yr period related to injuries sustained on the trampoline (11). Injury is a risk involved when undertaking any type of sport, especially when more than one individual is involved (18,19,21). Injury reports essentially are unchanged from earlier literature, but the most recent references available are from England, Ireland, New York, and Germany, which belies the ever-spreading dissemination of trampoline (17,25,28,30,37).
Adult supervision and the use of nets that surround the trampoline are common "safety" practices. Unfortunately, as reported by Eberl et al., 56.6% of the children and adolescents referred to their office were injured on a trampoline that had a safety net (14). The majority of severe injuries that occur do not involve falling or bouncing off of the trampoline; rather, they occur when multiple children bounce on the trampoline (24,25,30,34) or when individuals attempt maneuvers for which they are not trained and land on their head or neck (17). In a review of injuries in Finland by Rattya et al., 86% of the injuries presented involved a child who was bouncing on a trampoline with at least one other person. They suggested that using "safety netting" and adherence to safety instructions provided by trampoline manufacturers and governing bodies could prevent half of the injuries sustained (35). This study did not prove that these steps decrease the severity or incidence of injuries.
Frequently, the youngest or smallest child on the trampoline is the most likely to be injured when multiple children are bouncing (25,28). Despite the current AAP recommendation that trampolines should never be used in a home environment (current AAP statement), the popularity of this recreational activity has continued to increase; the subsequent increase in trampoline-related traumas has caused elevated concern among physicians and other health-care professionals (17,25,30,38) (Fig.).
The AAOS position statement on trampoline safety, originally published in 1996 and revised in 2005 in response to the 211,646 reported injuries sustained to children under the age of 19 in 2003, includes a number of guidelines for safe trampoline use (1). These guidelines do not differ significantly from those of competitive trampolining, which will be detailed later in this article. Adult supervision is a critical aspect to safe trampolining and is emphasized as such by governing bodies such as the AAOS and AAP. The AAOS recommendations include that only one person jump on the trampoline at one time, that they should not be used residentially without supervision, and that no child under the age of 6 yr should use the trampoline. Of interest is the guideline stating that safety nets may give a false sense of security to trampoline users, in view of the fact that most injuries occur on the trampoline and not from falling off. They also emphasize the need for frequent inspection of the equipment and ensuring adequate padding (1) (Table).
In Germany, 16.8% of gymnastic school sports injuries occurred while using a mini- and competition trampolines (26); this activity was third only to the vault and floor exercises as a cause of injury. The most common trampoline injuries that occurred in this competitive population were contusions and fractures. One factor that separates this population from the general population is training and potentially level of supervision. In a study by Linakis et al., the researchers found that 95% of injuries occur on home trampolines (29). However, this also may reflect the relatively lower number of individuals competing in trampolining, although almost all gymnasts use mini-trampolines as a training device. For example, it has been reported that out of the 91,000 individuals competing in United States Gymnastic Association, only 5,400 are competing in trampoline (45). Unlike children playing on trampolines at home, these athletes are trained in how to properly execute flips, jumps, and series of maneuvers in a somewhat more controlled environment; however, that does not mean the risk for serious injury is eliminated.
In 2000, trampoline was introduced into the Olympic Games in Sydney. While three variations of trampoline exist, only one is performed at the Games. This form involves completing a sequence of 10 acrobatic skills characterized by flight time and fall risk on a 14 × 7-ft trampoline (20,23). The other two variations include synchronized trampoline and double mini-trampoline. Synchronized trampoline is similar in nature to traditional trampoline: a series of 10 skills are performed, but by two athletes who are judged on both their skill level as well as synchronization (23). In double mini-trampoline, the movements are more lateral; the gymnast starts off running and performs a skill on the first mini-trampoline, immediately followed by impacting the second mini-trampoline before landing on the mat (23). All three variations are allowed at the World Championships.
The mini-trampoline is used extensively in many gyms as a training device. There are no reports of injury incidence specific to these devices. There is evidence that they clearly are not a safer alternative to large trampolines when used recreationally (38).
Injury is a great concern; however, there also may be underlying issues that makes gymnasts, particularly girls and women, more susceptible to traumas such as fracture. In an elite athlete population, particularly aesthetic sports (e.g., gymnastics, trampoline, swimming, diving), an emphasis is placed on physical appearance and body weight. These athletes can go to great lengths to maintain what they view as appropriate figures. The female athlete triad combines low energy availability (with or without eating disorder), amenorrhea, and osteoporosis (33). Low bone mineral density increases fracture risk in any population. During childhood and adolescence, the ages of most trampoline competitors, the greatest bone mineral density accrual occurs; if athletes miss this opportunity to maximize their bone mineral density, they are putting their skeleton at great risk for stress fractures and injuries later in life (33). A study by Schevchenko et al. remained consistent with previous findings that the gymnasts who started training young and trained the most intensely had hormonal imbalances and low body fat (36). The data suggest overtraining and/or low-caloric intake, which puts overall health at risk.
Stress urinary incontinence (SUI) is a reported condition in trampolinists. While not related to injury, it may be a source of embarrassment and potentially cause long-term dysfunction in competitive trampolinists. As reported by Eliasson et al., SUI occurs in 80% of the competitive trampolinists surveyed (15). This study examined 35 elite female trampolinists and factors that influenced the occurrence included both age and duration/intensity of training. Generally, physically fit individuals have strong pelvic floor muscles (PFM); however, during trampoline jumping, a large amount of force is placed on the PFMs, and SUI can result despite normal PFM strength. It is unclear whether there are any long-term implications for these athletes (15). Caylet et al. published a study examining SUI among elite female athletes regardless of sport and compared them with an age-matched control population (9). The prevalence of SUI, in this situation, was 28% of elite female athletes compared with 9.8% of controls. SUI is a condition that is more prevalent in competitive female athletes, exceptionally so in trampolinists. Little information is available in the literature regarding treatment and prevention of SUI in trampolinists; more prospective longitudinal studies need to be completed to examine risk for SUI and potential long-term consequences.
Current Safety Recommendations for Competitive Trampolining
The United States Tumbling & Trampoline Association (USTA) provides guidelines for safe practice of the various trampoline exercises (44). These guidelines were designed to protect the athlete throughout practice and competition. Examples of individual trampoline/synchronized trampoline guidelines are as follows: No student or performer should ever attempt to execute any trampoline skill unless that skill has first been taught properly to the student by a qualified instructor, and no one, regardless of ability level, should ever use a piece of trampoline equipment unless they are under the direct supervision of a qualified instructor. Two people should never jump on the same trampoline at the same time, and no horseplay should ever be allowed on the trampoline (44). Additional safety recommendations include, but are not limited to, setup of equipment, avoidance of drugs/alcohol, and use when fatigued. A separate, similar set of guidelines are available for mini-trampoline safety (44).
The AAP, AAOS, and USTA all concur that two or more people should never use a trampoline at the same time. This recommendation involves both competitive trampolining as well as recreational use of a trampoline. The literature and the senior author's experience is consistent in reporting that the greatest number of injuries occur when more than one person is on a trampoline and that the smallest individual is the most likely to be injured. The one factor that would most likely reduce injuries in children and adolescents with both recreational and competitive trampoline use would be to adhere to the myriad of consistent safety rules, especially having mature adult supervision, which is lacking in most instances of injury (1).
Little reported data are available on injury type or rate in elite competitive trampoline; rather, injuries are reported in conjunction with other gymnastic sports. It would be intuitive that the injury risk and severity potentially would be higher as the complexity of techniques increases and the markedly greater altitude that can be generated from competitive trampolines.
There is an apparent lack of awareness of the significant risks for major life-changing injury and even death by the majority of individuals and families who participate in trampoline use either recreationally or competitively, despite extensive efforts at public education by multiple advocacy groups. Short of legislating them out of existence, it is anticipated that the number of injuries will continue to increase, worldwide.
Competitive trampolinists and gymnasts should be counseled as to the risks and only perform complex techniques under appropriate supervision and skilled instruction. Increasing complexity of routines will lead to a greater risk of severe injury. The energy imparted by modern competitive trampolines leads to velocities and achievable heights far in excess of backyard trampolines that will make spotting and pads less than optimal in preventing injuries.
It is the authors' opinion that an objective evaluation and compilation of injury incidence, type, and severity, by the responsible gymnastic organizational bodies, in conjunction with the sports medicine community, is necessary to assess the incidence and severity of injuries when competing or training with a trampoline. Only with such a comprehensive assessment can it be determined, from an injury risk standpoint, if trampolines can be used with an acceptable degree of safety in competition and training. At this time, the authors support the position statements of the AAOS and AAP that trampolines cannot be used safely for recreational purposes.
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