Video Abstract
Trampolines are an important cause of childhood injury and focus of injury prevention. Understanding and prevention of trampoline park injury is constrained by inadequate exposure data to estimate the at-risk population. This study aimed to measure trampoline park injury incidence and time trends using industry data.
Cross-sectional study to retrospectively analyze reported injuries and exposure in 18 trampoline parks operating in Australia and the Middle East, from 2017 to 2019. Exposure was derived from ticket sales and expressed as jumper hours. Exposure-adjusted incidence was measured using marginalized 0-inflated Poisson modeling and time trends using Joinpoint regression.
There were 13 256 injured trampoline park users reported from 8 387 178 jumper hours; 11% sustained significant injury. Overall, trampoline park injuries occurred at a rate of 1.14 injuries per 1000 jumper hours (95% confidence intervals 1.00 to 1.28), with rates highest for high-performance (2.11/1000 jumper hours, 1.66 to 2.56) and inflatable bag or foam pit (1.91/1000 jumper hours, 1.35 to 2.50) jumping. Significant injuries occurred at a rate of 0.11 injuries per 1000 jumper hours (0.10 to 0.13), with rates highest for high-performance (0.29/1000 jumper hours, 0.23 to 0.36), and parkour (0.22/1000 jumper hours, 0.15 to 0.28) jumping. Overall, injury rates decreased by 0.72%/month (−1.05 to −0.40) over the study period.
Trampoline park injuries occur in important numbers with sometimes serious consequences. However, within these safety standard-compliant parks, exposure-adjusted estimates show injuries to be uncommon and injury rates to be declining. Further reductions are required, especially severe injuries, and this study can enhance injury prevention initiatives.
What’s Known on This Subject:
Trampoline use at homes or trampoline parks is an important cause of childhood injury, including severe injury, and a focus for injury prevention. Measuring trampoline park injury has been challenging because of inadequate exposure data to define the at-risk population.
What This Study Adds:
Trampoline park injuries occur in important numbers with sometimes serious consequences. However, within standard-compliant parks, exposure-adjusted estimates show injuries are uncommon and rates are declining. Further reductions are required, especially severe injuries, and this study can enhance injury prevention initiatives.
Trampoline parks are popular indoor recreational facilities typified by wall-to-wall connected trampolines with padded or angled-trampoline walls, purpose-built to entertain large groups in close proximity.1,2 Since the first trampoline park opened in 2004, the industry has grown rapidly with more than 1500 parks in operation globally.3 Although trampoline parks are promoted as fun and child-friendly, they have also been reported to pose significant injury risk.4–8 For example, Williams et al identified 18 716 US children injured in trampoline parks between 2009 and 2017,9 and Choi et al reported 2126 South Korean children with trampoline park injuries over a similar 6-year period.10 Such injury estimates have put a spotlight on trampoline parks as an emerging source of childhood injury,7,8,11–14 prompting critical media attention and calls for increased regulation and standards.4–8 Given this injury burden and potential for lifelong disability after serious injury, efforts to enhance trampoline park safety are unequivocally important.
Measuring trampoline park injury incidence has proved problematic, despite recognition that accurate determination of incidence is essential to priority setting, implementation, and evaluation of public health practice.15 To accurately measure incidence, estimation of the at-risk population is also required, as is well established for transport-related injury (eg, distance and hours traveled),16,17 and sport injury (eg, number of athletes and hours played).18 Failure to derive exposure-adjusted estimates of trampoline park injury has hindered robust evaluation of injury risk and evidence-based dialogue about the risks and benefits of trampoline parks. This study aimed to quantify the exposure-adjusted incidence of trampoline park injuries, and assess for trends in injury rates over time, through collaboration with 3 established trampoline park operators to obtain industry data for injured park users as well as ticket sales numbers for all active park users.
Methods
Study Design
A cross-sectional study was performed with retrospective analysis of all reported injury and exposure data in trampoline parks run by 3 well-established operators, for the period January 1, 2017 to December 31, 2019. Exposure data were derived from park ticket sales and are expressed as jumper hours.
Setting
Deidentified injury data and monthly jumper hour tallies were provided by BOUNCEinc Australia (AU; 8 parks), BOUNCEinc Middle East (ME; 8 parks), and Sky Zone (AU; 4 parks). Two BOUNCEinc (ME) parks were excluded because of incomplete data. Thus, analyses included data from 18 trampoline parks, which opened progressively between August 2012 and December 2018. The median venue capacity for these parks was 140 (range 100–200) users per hour, with daily opening hours varying from 8 to 12 hours. All 3 operators reported that their parks complied with the Australian Trampoline Parks Association (ATPA) safety standards.19
Trampoline Park Injury Data
Injury Severity Classification
Trampoline park employees completed contemporaneous injury reports with defined data entry fields, including injury severity classification using standardized industry definitions. Before March 2018, BOUNCEinc classified injuries as minor or significant (or undecided) using definitions based on ATPA standards19 (Table 1). In March 2018, BOUNCEinc adopted the International Adventure and Trampoline Parks Association (IATP) system, which classifies injuries into 5 grades (Table 1). Sky Zone (AU) used the IATP severity classification system throughout the study. All 3 operators systematically followed-up with injured clients to finalize injury details, with or without revision according to any new information, especially if initially classified as “undecided.” This study considered the finalized injury details and classified injuries as minor (IATP 0–2) or significant (IATP 3–4). Of note, until March 2018, BOUNCEinc classified some injuries as “minor,” which the later-adopted IATP system would have deemed to be grade 3 and so “significant,” eg, serious ligamentous injuries and injuries requiring surgery (Table 1). To resolve this, any injury meeting IATP grade 3 criteria was classified as significant. In addition, any injuries resulting in ambulance attendance were classified as significant.
Trampoline Park Operator-used Injury Severity Classification Systems
| System | Minor Injury | Significant Injury |
|---|---|---|
| ATPA | • Small cuts, lacerations or abrasions; • ankle; sprained or rolled; • back; jarred or sprained; • neck; sprained; • knee; jarred or sprained; • dislocations; • ACL tears or other serious ligament damagea; • requiring surgerya | • Broken bones; • spinal injury; • lacerations requiring immediate medical attention; • electric shock requiring immediate medical attention; • head or eye injury requiring immediate medical attention; • loss of bodily function; • unconsciousness; • death |
| IATP | Grade 0: all first aid intervention that does not fall into grade 1, 2, 3 or 4 categories. An example would be the issue of a plaster to cover a pre-existing cut before jumping. | Grade 3: any injury sustained in the park that requires professional medical intervention to rectify (above and beyond rest, ice, compression, elevation) but does not fall into the category of a grade 4 (life-changing) injury. Examples would be fractures of any kind, tendon or ligament damage or muscular damage that require further medical intervention beyond the initial diagnosis. |
| Grade 1: any injury that requires the intervention of a “first-aider” but does not prevent the injured party from being capable of continuing to jump. Examples would be minor cuts, a small friction burn, or an incident resulting in a small bruise or suspected strain. | ||
| Grade 2: any injury that requires the intervention of a first-aider and prevents the injured party from being capable of continuing to jump. If the injured party then chooses to seek medical advice after the event, the outcome shall not fall into grade 3 or 4 category. | Grade 4: any injury that causes or results in the death of a participant or alters the quality of the rest of their life. Examples would be paralysis, nerve damage or limb amputation. |
| System | Minor Injury | Significant Injury |
|---|---|---|
| ATPA | • Small cuts, lacerations or abrasions; • ankle; sprained or rolled; • back; jarred or sprained; • neck; sprained; • knee; jarred or sprained; • dislocations; • ACL tears or other serious ligament damagea; • requiring surgerya | • Broken bones; • spinal injury; • lacerations requiring immediate medical attention; • electric shock requiring immediate medical attention; • head or eye injury requiring immediate medical attention; • loss of bodily function; • unconsciousness; • death |
| IATP | Grade 0: all first aid intervention that does not fall into grade 1, 2, 3 or 4 categories. An example would be the issue of a plaster to cover a pre-existing cut before jumping. | Grade 3: any injury sustained in the park that requires professional medical intervention to rectify (above and beyond rest, ice, compression, elevation) but does not fall into the category of a grade 4 (life-changing) injury. Examples would be fractures of any kind, tendon or ligament damage or muscular damage that require further medical intervention beyond the initial diagnosis. |
| Grade 1: any injury that requires the intervention of a “first-aider” but does not prevent the injured party from being capable of continuing to jump. Examples would be minor cuts, a small friction burn, or an incident resulting in a small bruise or suspected strain. | ||
| Grade 2: any injury that requires the intervention of a first-aider and prevents the injured party from being capable of continuing to jump. If the injured party then chooses to seek medical advice after the event, the outcome shall not fall into grade 3 or 4 category. | Grade 4: any injury that causes or results in the death of a participant or alters the quality of the rest of their life. Examples would be paralysis, nerve damage or limb amputation. |
ACL, anterior cruciate ligament.
Injuries classified as minor by ATPA but classified as grade 3 (significant) by IATP.
Park Activities
All trampoline parks provided jumpers with access to multiple activities during park use. Trampoline park activities are depicted in Fig 1 with additional descriptions in Table 2. To enable comparisons, we mapped similar activities between operators and parks, as outlined in Supplemental Table 6.
Trampoline park activities. Representative images of different trampoline park activities, showing jumpers (users) and supervising staff. (A) Free jump, (B) dodgeball, (C) inflatable bag (foam pit is similar in concept and practice), (D) slam dunk, (E) high-performance, (F) parkour area, (G) high ropes course (example nontrampoline activity), (H) battle beams (example nontrampoline activity). Images provided by BOUNCEinc (2022) with subject consent for use.
Trampoline park activities. Representative images of different trampoline park activities, showing jumpers (users) and supervising staff. (A) Free jump, (B) dodgeball, (C) inflatable bag (foam pit is similar in concept and practice), (D) slam dunk, (E) high-performance, (F) parkour area, (G) high ropes course (example nontrampoline activity), (H) battle beams (example nontrampoline activity). Images provided by BOUNCEinc (2022) with subject consent for use.
Descriptions of Trampoline Park Activities
| Activity | Activity Description |
|---|---|
| Free jump | Free jump involves a large playground of interconnected trampolines, tumble (sprung) tracks and banked or padded walls. Jumpers are restricted to a single trampoline. |
| Dodgeball | Dodgeball involves 2 opposing teams of jumpers throwing soft bowling ball-sized dodgeballs with the aim of striking an opposition team jumper. If struck by a dodgeball, a jumper is “out” and so excluded from the game. During the game, active jumpers are restricted to one of interconnected trampolines similar to those used for free jumping. The game continues until 1 team is fully excluded. |
| High-performance | High-performance involves jumpers aiming for more advanced training and skill progression, and utilizes trampolines geared for greater bounce and height than those used for other activities such as free jumping. |
| Parkour area | Parkour area involves users navigating various obstacles or features of varying levels of difficulty, with staff supervision at a recommended ratio of [insert ratio]. Users can approach features as stand-alone challenges or as a circuit, and either as an individual pursuit or paired in competition against another user. |
| Slam dunk | Slam dunk involves jumpers using runway trampolines (surrounded by padded walls and floor mats) to jump up to full-height basketball rings and ‘slam dunk’ soft, basketball-sized balls into the ring. |
| Inflatable bag or foam pit | Jumpers use runway trampolines or sprung tracks to attempt various jumps or tricks before landing softly onto inflatable bags, or into a foam pit depending on the specific park scenario. Jumpers take it in turns to use the inflatable bag (or foam pit) one at a time. |
| Nontrampoline activities | Parks may have any number of nontrampoline activities, such as harnessed users scaling rock climbing walls or traversing high ropes courses, and “battle beam” in which 2 users stand on a thin beam and “battle” with soft paddles to be the last person standing or fall into a foam pit. A full list of nontrampoline activities for each operator in this study is provided in Supplemental Table 1. |
| Activity | Activity Description |
|---|---|
| Free jump | Free jump involves a large playground of interconnected trampolines, tumble (sprung) tracks and banked or padded walls. Jumpers are restricted to a single trampoline. |
| Dodgeball | Dodgeball involves 2 opposing teams of jumpers throwing soft bowling ball-sized dodgeballs with the aim of striking an opposition team jumper. If struck by a dodgeball, a jumper is “out” and so excluded from the game. During the game, active jumpers are restricted to one of interconnected trampolines similar to those used for free jumping. The game continues until 1 team is fully excluded. |
| High-performance | High-performance involves jumpers aiming for more advanced training and skill progression, and utilizes trampolines geared for greater bounce and height than those used for other activities such as free jumping. |
| Parkour area | Parkour area involves users navigating various obstacles or features of varying levels of difficulty, with staff supervision at a recommended ratio of [insert ratio]. Users can approach features as stand-alone challenges or as a circuit, and either as an individual pursuit or paired in competition against another user. |
| Slam dunk | Slam dunk involves jumpers using runway trampolines (surrounded by padded walls and floor mats) to jump up to full-height basketball rings and ‘slam dunk’ soft, basketball-sized balls into the ring. |
| Inflatable bag or foam pit | Jumpers use runway trampolines or sprung tracks to attempt various jumps or tricks before landing softly onto inflatable bags, or into a foam pit depending on the specific park scenario. Jumpers take it in turns to use the inflatable bag (or foam pit) one at a time. |
| Nontrampoline activities | Parks may have any number of nontrampoline activities, such as harnessed users scaling rock climbing walls or traversing high ropes courses, and “battle beam” in which 2 users stand on a thin beam and “battle” with soft paddles to be the last person standing or fall into a foam pit. A full list of nontrampoline activities for each operator in this study is provided in Supplemental Table 1. |
Other Trampoline Park Injury Event Data
In addition to injury severity and trampoline park activity data, the following deidentified information were provided for all injuries: demographic information (age in years, sex), month and year of injury, and whether an ambulance was called to attend.
Exposure Data (population at risk for injury)
Each operator reported the number of park users according to monthly ticket sales, where each ticket sold enabled access to the park for 1 hour. We assumed that each ticketholder used the park for the full available hour, and so equated each ticket to 1 jumper hour. Onlookers, such as parents or nonparticipating siblings, do not purchase tickets and are not included in the jumper hour exposure data.
Activity-specific exposure and injury rates were calculated using proportional weightings. Each activity in each trampoline park had a defined capacity limit on the number of users at any one time, the sum of all activity capacity limits equaling the park capacity. Operators provided activity limit and park capacity data, including the dates and nature of any park layout alterations that changed capacity data during the study period. These park-specific activity capacity limits were used to calculate the proportion of total park users that could be using each activity within each park at any one time. This proportional weighting was then applied to the sum of jumper hours for a given park to estimate the jumper hours specific to each activity in each park. These proportional weightings assumed the distribution of users was consistent, irrespective of whether the park was at full or below-full capacity. Where applicable, weightings were updated in time-specific manner to reflect park layout changes.
Incidence Description and Terminology
Exposure-adjusted incidence rates were expressed as injuries per 1000 jumper hours. In this study, a typical trampoline park had capacity for 140 users per hour, in which setting, 1000 jumper hours equates to just over 7 hours of venue operation at full capacity. Terminology used to describe incidence complied with Council for International Organizations of Medical Science convention: very common, ≥1 of 10; common, ≥1 of 100 and <1 of 10; uncommon, ≥1 of 1000 and <1 of 100; rare, ≥1 of 10 000 and <1 of 1000; very rare: <1 of 10 000.20
Inclusion Criteria
All reported injured park users and monthly jumper hour tallies provided by the trampoline park operators were included. There were no age-related exclusion criteria as all ages were allowed to access these parks, and age was not recorded for all ticketed park users, only injured users.
Statistical Methods
Adjusted Injury Rate Modeling
Marginalized 0-inflated Poisson (MZIP) models were used to calculate injury rates adjusted for exposure (per 1000 jumper hours). The injury data distribution for this study exhibited a notable percentage of 0s for injuries of any (all) severity (28%), and very high percentage of 0s for significant injuries (77%). The 0 count rendered the Poisson regression inadequate in describing these data, potentially resulting in incorrect estimates and biased standard errors. The 0-inflated Poisson regression model generated 2 sets of regression with latent class interpretations: 1 for the Poisson mean; the other for the probability of being an excess 0. The MZIP model estimated the marginal mean and coefficients are interpreted as the population-averaged parameters. Two MZIP models were developed: Model 1 included injuries of any (all) severity and adjusted for operator (BOUNCEinc [AU], BOUNCEinc [ME], Sky Zone [AU]), trampoline park activity, and month of the year. Model 2 included significant injuries only and adjusted for operator and park activity, but month of the year was excluded because of convergence issues.
Time Trend Analysis
Monthly injury counts and jumper hours were summed and transformed into a rate per 1000 jumper hours for total and across operator, trampoline park, and park activity. Joinpoint regression was applied to assess changes in time series data for total injuries. This method of regression assumes that data can be divided into subsets with their own unique linear trend and has been used to investigate time trends in other health settings.21,22 Here, Joinpoint regression was used to obtain accurate estimates of changes in injury rates and to provide a complete understanding of the injury population dynamics for this cohort. Crude monthly injury rates (1 to 36 months, reflecting January 2017 to December 2019) were modeled, using first order autocorrelation from the data with data-driven Bayesian Information Criterion (BIC) method to select the best model.23 The Weighted Bayesian Information Criterion criterion was used for the model selection. This measure combines the BIC and a stricter penalty than the traditional BIC using BIC3 via a weighted penalty term based on the data characteristics; for formulas, please refer to Joinpoint Help Manual 4.8.0.1.24 The empirical quartile method was used to define 95% confidence intervals (CI), with 10000 resamples. Models were run for total and across operator, trampoline park, and activity for that park, and residual analysis was performed to check the regression assumptions were not violated.
Analysis Software
Data analyses were performed using Stata (Version 15.1, StataCorp, College Station, TX) and Joinpoint Regression Program (Version 4.9.0.0. March 2021, Statistical Methodology and Applications Branch, Surveillance Research Program, National Cancer Institute).
Ethical Considerations
This study was approved by The Royal Children’s Hospital Human Research and Ethics Committee (#HREC 36089A, #DA041-2015-08). All operators provided deidentified data and had no influence or input into the design, performance, or interpretation of analyses. The study was conducted without trampoline park industry financial support, direct or indirect, and the study team had no financial or other relationship to any park operator.
Results
Descriptive Statistics
Over the 3-year study period, the 18 trampoline parks reported a total of 13 256 injuries: 11 825 (89.2%) were minor and 1431 (10.8%) were significant injuries. Overall, trampoline park injuries were most common in 10 to 14 year olds (41.3%) and 5 to 9 year olds (24.6%), and occurred in more males (58.6%) than females. Injuries were most common when users were free jumping (30.9%) and high-performance jumping (20.2%) (Table 3).
Injured Trampoline Park User Characteristics
| Any (all) Injury, N (%) | Minor Injury, N (%) | Significant Injury, N (%) | P | |
|---|---|---|---|---|
| n = 13 256 | n = 11 825 | n = 1431 | ||
| Age categorya | <.001 | |||
| 0–4 y | 232 (1.8) | 195 (1.7) | 37 (2.6) | |
| 5–9 y | 3223 (24.6) | 2990 (25.5) | 233 (16.6) | |
| 10–14 y | 5415 (41.3) | 4874 (41.6) | 541 (38.6) | |
| 15–19 y | 1663 (12.7) | 1461 (12.5) | 202 (14.4) | |
| 20–29 y | 1729 (13.2) | 1481 (12.6) | 248 (17.7) | |
| 30–39 y | 548 (4.2) | 466 (4.0) | 82 (5.9) | |
| 40 plus years | 309 (2.4) | 251 (2.1) | 58 (4.1) | |
| Sexb | 0.65 | |||
| Male | 7760 (58.6) | 6930 (58.6) | 830 (58.0) | |
| Female | 5492 (41.4) | 4891 (41.4) | 601 (42.0) | |
| Activityc | <.001 | |||
| Free jump | 4102 (30.9) | 3658 (30.9) | 444 (31.0) | |
| Dodgeball | 1507 (11.4) | 1388 (11.7) | 119 (8.3) | |
| Inflatable bag or foam pit | 1917 (14.5) | 1729 (14.6) | 188 (13.1) | |
| Slam dunk | 394 (3.0) | 354 (3.0) | 40 (2.8) | |
| High performance | 2675 (20.2) | 2351 (19.9) | 324 (22.6) | |
| Parkour area | 1907 (14.4) | 1649 (13.9) | 258 (18.0) | |
| Nontrampoline activities | 373 (2.8) | 336 (2.8) | 37 (2.6) | |
| Nonactive areas | 356 (2.7) | 336 (2.8) | 20 (1.4) | |
| Unknown | 25 (0.2) | 24 (0.2) | 1 (0.1) | |
| Park operator | <.001 | |||
| BOUNCEinc (AU) | 8932 (67.4) | 8149 (68.9) | 783 (54.7) | |
| BOUNCEinc (ME) | 2524 (19.0) | 2223 (18.8) | 301 (21.0) | |
| Sky Zone (AU) | 1800 (13.6) | 1453 (12.3) | 347 (24.2) |
| Any (all) Injury, N (%) | Minor Injury, N (%) | Significant Injury, N (%) | P | |
|---|---|---|---|---|
| n = 13 256 | n = 11 825 | n = 1431 | ||
| Age categorya | <.001 | |||
| 0–4 y | 232 (1.8) | 195 (1.7) | 37 (2.6) | |
| 5–9 y | 3223 (24.6) | 2990 (25.5) | 233 (16.6) | |
| 10–14 y | 5415 (41.3) | 4874 (41.6) | 541 (38.6) | |
| 15–19 y | 1663 (12.7) | 1461 (12.5) | 202 (14.4) | |
| 20–29 y | 1729 (13.2) | 1481 (12.6) | 248 (17.7) | |
| 30–39 y | 548 (4.2) | 466 (4.0) | 82 (5.9) | |
| 40 plus years | 309 (2.4) | 251 (2.1) | 58 (4.1) | |
| Sexb | 0.65 | |||
| Male | 7760 (58.6) | 6930 (58.6) | 830 (58.0) | |
| Female | 5492 (41.4) | 4891 (41.4) | 601 (42.0) | |
| Activityc | <.001 | |||
| Free jump | 4102 (30.9) | 3658 (30.9) | 444 (31.0) | |
| Dodgeball | 1507 (11.4) | 1388 (11.7) | 119 (8.3) | |
| Inflatable bag or foam pit | 1917 (14.5) | 1729 (14.6) | 188 (13.1) | |
| Slam dunk | 394 (3.0) | 354 (3.0) | 40 (2.8) | |
| High performance | 2675 (20.2) | 2351 (19.9) | 324 (22.6) | |
| Parkour area | 1907 (14.4) | 1649 (13.9) | 258 (18.0) | |
| Nontrampoline activities | 373 (2.8) | 336 (2.8) | 37 (2.6) | |
| Nonactive areas | 356 (2.7) | 336 (2.8) | 20 (1.4) | |
| Unknown | 25 (0.2) | 24 (0.2) | 1 (0.1) | |
| Park operator | <.001 | |||
| BOUNCEinc (AU) | 8932 (67.4) | 8149 (68.9) | 783 (54.7) | |
| BOUNCEinc (ME) | 2524 (19.0) | 2223 (18.8) | 301 (21.0) | |
| Sky Zone (AU) | 1800 (13.6) | 1453 (12.3) | 347 (24.2) |
P value for comparison of minor versus significant injury.
Missing data for age category, n = 137 (1.0%).
Missing data for sex category, n = 4 (0.0%).
Exposure-adjusted Trampoline Park Injury Rates
Over the 3-year period, the 18 parks reported a total of 8 387 178 jumper hours. Based on this total exposure, the crude overall trampoline park injury rates for the study were: 1.58 injuries of any (all) severity per 1000 jumper hours, and 0.17 significant injuries per 1000 jumper hours.
MZIP model 1 for injuries of any (all) severity derived an adjusted overall trampoline park injury rate of 1.14 injuries per 1000 jumper hours (95% CI: 1.00 to 1.28) (Supplemental Table 7). As such, trampoline park injuries of any (all) severity are uncommon, with 1 injury every 877 jumper hours. MZIP model 2 derived an adjusted significant trampoline park injury rate of 0.11 injuries per 1000 jumper hours (95% CI: 0.10 to 0.13) (Supplemental Table 8). As such, significant trampoline park injuries are rare, with 1 significant injury every 9090 jumper hours.
Trampoline Park Injuries of Any (all) Severity According to Activity, Operator, and Park
Adjusted rates for trampoline park injury of any (all) severity varied substantially between park activity (Fig 2A, Table 4A), operators (Fig 2A, Supplemental Table 8) and parks (Supplemental Table 9).
Exposure-adjusted rates of trampoline park injury - overall, by activity and by operator. (A) Rates of injuries of any (all) severity, (B) rates of significant injuries only. Further details of trampoline park activities are provided by Figure 1 and Supplemental Tables 2,3. AU, Australia. ME, Middle East.
Exposure-adjusted rates of trampoline park injury - overall, by activity and by operator. (A) Rates of injuries of any (all) severity, (B) rates of significant injuries only. Further details of trampoline park activities are provided by Figure 1 and Supplemental Tables 2,3. AU, Australia. ME, Middle East.
Ranking of Trampoline Park Activity by Injury Rate
| A: Rates of Injuries of Any (All) Severity | |||
|---|---|---|---|
| Rank | Activitya | Injury Rate / 1000 Jumper Hours (95% CI) | Incidence Descriptora |
| 1 | High performance | 2.11 / 1000 h (1.66 to 2.56) | Uncommon |
| 2 | Inflatable bag or foam pit | 1.92 / 1000 h (1.35 to 2.50) | Uncommon |
| 3 | Free jumping | 1.87 / 1000 h (1.65 to 2.09) | Uncommon |
| 4 | Parkour area | 1.35 / 1000 h (1.02 to 1.68) | Uncommon |
| 5 | Dodgeball | 1.20 / 1000 h (0.94 to 1.46) | Uncommon |
| 6 | Nontrampoline activities | 0.65 / 1000 h (0.38 to 0.93) | Rare |
| 7 | Slam dunk or sky slam | 0.58 / 1000 h (0.37 to 0.80) | Rare |
| 8 | Nonactive areas | 0.56 / 1000 h (0.35 to 0.76) | Rare |
| B: Rates of Significant Injuries Only | |||
| Rank | Activitya | Injury Rate / 1000 Jumper Hours (95% CI) | Incidence Descriptorb |
| 1 | High performance | 0.29 / 1000 h (0.23 to 0.36) | Rare |
| 2 | Parkour area | 0.22 / 1000 h (0.15 to 0.28) | Rare |
| 3 | Inflatable bag or foam pit | 0.20 / 1000 h (0.14 to 0.26) | Rare |
| 4 | Free jumping | 0.20 / 1000 h (0.17 to 0.23) | Rare |
| 5 | Dodgeball | 0.09 / 1000 h (0.07 to 0.11) | Very rare |
| 6 | Nontrampoline activities | 0.07 / 1000 h (0.03 to 0.11) | Very rare |
| 7 | Slam dunk | 0.06 / 1000 h (0.03 to 0.09) | Very rare |
| 8 | Nonactive areas | 0.03 / 1000 h (0.02 to 0.05) | Very rare |
| A: Rates of Injuries of Any (All) Severity | |||
|---|---|---|---|
| Rank | Activitya | Injury Rate / 1000 Jumper Hours (95% CI) | Incidence Descriptora |
| 1 | High performance | 2.11 / 1000 h (1.66 to 2.56) | Uncommon |
| 2 | Inflatable bag or foam pit | 1.92 / 1000 h (1.35 to 2.50) | Uncommon |
| 3 | Free jumping | 1.87 / 1000 h (1.65 to 2.09) | Uncommon |
| 4 | Parkour area | 1.35 / 1000 h (1.02 to 1.68) | Uncommon |
| 5 | Dodgeball | 1.20 / 1000 h (0.94 to 1.46) | Uncommon |
| 6 | Nontrampoline activities | 0.65 / 1000 h (0.38 to 0.93) | Rare |
| 7 | Slam dunk or sky slam | 0.58 / 1000 h (0.37 to 0.80) | Rare |
| 8 | Nonactive areas | 0.56 / 1000 h (0.35 to 0.76) | Rare |
| B: Rates of Significant Injuries Only | |||
| Rank | Activitya | Injury Rate / 1000 Jumper Hours (95% CI) | Incidence Descriptorb |
| 1 | High performance | 0.29 / 1000 h (0.23 to 0.36) | Rare |
| 2 | Parkour area | 0.22 / 1000 h (0.15 to 0.28) | Rare |
| 3 | Inflatable bag or foam pit | 0.20 / 1000 h (0.14 to 0.26) | Rare |
| 4 | Free jumping | 0.20 / 1000 h (0.17 to 0.23) | Rare |
| 5 | Dodgeball | 0.09 / 1000 h (0.07 to 0.11) | Very rare |
| 6 | Nontrampoline activities | 0.07 / 1000 h (0.03 to 0.11) | Very rare |
| 7 | Slam dunk | 0.06 / 1000 h (0.03 to 0.09) | Very rare |
| 8 | Nonactive areas | 0.03 / 1000 h (0.02 to 0.05) | Very rare |
Incidence descriptors as per Council for International Organizations of Medical Sciences20 : very common, ≥1 of 10; common, ≥1 of 100 and <1 of 10; uncommon, ≥1 of 1000 and <1 of 100; rare, ≥1 or 10 000 and <1 or 1000; very rare: <1 or 10 000.
Adjusted overall trampoline park injury rates were highest for high-performance jumping (2.11 injuries per 1000 jumper hours; 95% CI: 1.66 to 2.56), inflatable bag or foam pit activity (1.91 injuries per 1000 jumper hours; 95% CI: 1.35 to 2.50), and free jumping (1.87 injuries per 1000 jumper hours; 95% CI 1.65 to 2.09). Adjusted overall injury rates were lowest in nonactive areas (0.56 injuries pe 1000 jumper hours; 95% CI: 0.35 to 0.76) and slam dunk (0.58 injuries per 1000 jumper hours; 95% CI: 0.37 to 0.80) (Fig 2A, Table 4A).
Significant Trampoline Park Injuries According to Activity, Park, and Operator
Adjusted rates for significant injuries varied substantially between park activities (Fig 2B, Table 4B). Adjusted significant injury rates were highest for high performance jumping (0.29 significant injuries per 1000 jumper hours; 95% CI: 0.23 to 0.36), and parkour area (0.22 significant injuries per 1000 jumper hours; 95% CI: 0.15 to 0.28). Except for relatively higher rates of significant injuries in the parkour area, the ranking of activities according to rates of significant injury mirrors that for trampoline park injuries of any (all) severity (Table 4). Adjusted significant injury rates also varied between operators (Fig 2B, Supplemental Table 8) and parks (Supplemental Table 10).
Time Trend Analysis
For trampoline park injuries of any (all) severity, the Joinpoint regression analysis identified a significant downward trend in overall injury rate, with a 0.72% (95% CI: −1.05 to −0.40) rate reduction per month from January 2017 to December 2019 (Fig 3A). The time trends of trampoline park injuries of any (all) severity varied between operators, with analyses revealing a more complex picture, including periods of significant increase and decline of injury rates for all 3 operators (Supplemental Material).
Temporal trends for rates of trampoline park injury. (A) Rates of injuries of any (all) severity, (B) rates of SIGNIFICANT injuries only. * Indicates that the Monthly Percent Change (MPC) is significantly different from zero at the α = .05 level.
Temporal trends for rates of trampoline park injury. (A) Rates of injuries of any (all) severity, (B) rates of SIGNIFICANT injuries only. * Indicates that the Monthly Percent Change (MPC) is significantly different from zero at the α = .05 level.
Time Trend Analyses Limited to Significant Trampoline Park Injury
Joinpoint regression analysis related to significant trampoline park injuries demonstrated distinct variations in injury rate over time (Fig 3B). The significant injury rate: (1) fell from January 2017 to June 2017 by 6.61% per month (95% CI: −20.99 to 0.26), then (2) rose by 1.69% per month (95% CI: 0.39 to 11.23) until June 2018, at which point (3) it fell sharply by 16.16% per month (95% CI: −20.91 to −2.89) from June 2018 to October 2018, only to (4) rise again by 3.49% per month (95% CI: 1.21 to 7.29) until the end of the study period in December 2019. Again, operator-specific analyses revealed differences in the time trends for rates of significant trampoline park injuries between operators (Supplemental Material).
Discussion
This study provides robust exposure-adjusted injury rates for trampoline park injuries. This addresses key deficits in the evidence regarding trampoline park injuries, which is dominated by studies simply reporting the total number of injuries occurring over a specified period. Our measurement of exposure-adjusted injury incidence enables new and improved opportunities for risk-based decision-making for trampoline park operators, consumers, and health advocates, as well as better design and assessment of injury prevention interventions.
In distinction to prior studies, the current study analyzed industry-provided injury data with the aim of capturing all injured trampoline park users. This includes some injured who might evade reporting by single-center series12,13,25–28 or health surveillance registries,1,9,10,14,29 as they are managed at home or within the primary health setting. Consistent with prior studies,1,9,10,12–14,25–29 we identified a high number of injuries occurring in trampoline parks. This affirms the reality of trampoline use and parks as contributors to the overall burden of injury. However, by utilizing exposure data from trampoline parks, the current study has provided a more robust measurement of injury risk.
Notwithstanding the total number, reframing trampoline park injuries through the lens of exposure-adjusted rates reveals these to be uncommon and rare events according to severity, activity, or park specific qualifiers. Further, although the number of injuries may increase in register with the growing popularity (and so exposure) of trampoline parks,7,8 the exposure-adjusted modeling in this study shows an overall trend of reduction in the incidence of injuries over time. We would argue that this juxtaposition should not lessen concerns raised by the burden of trampoline park injuries, but rather moderate the way in which health and industry stakeholders respond to and message these concerns.
The exposure-adjusted estimates of this study also provide new opportunity to meaningfully compare rates of trampoline park injuries with those of other common physical activities. Table 5 provides estimated exposure-adjusted injury rates for other activities popular with children, eg, Australian football, netball, and tennis.30–34 Although the methodologies and robustness of exposure data vary across these prior studies, it is clear that the rates of trampoline park injuries reported here compare favorably. The insights this affords should allow for a more nuanced narrative for injury prevention, and engagement with trampoline park operators and consumers. Shaped by more accurate estimations of risk, this discourse can be steered toward effective prevention and away from emotive sentiment and language, such as “alarm,”29 “threat,”35 and “children bouncing into the emergency department”.25
Exposure-adjusted Injury Rates for Various Popular Childhood Activities
| Study Period | Injury Rate | Incidence Descriptora | |
|---|---|---|---|
| Current study | |||
| Trampoline parks – any (all) injury | 2017–2019 | 1.14 / 1000 h | Uncommon |
| Trampoline parks – significant injury | 2017–2019 | 0.11 / 1000 h | Rare |
| Previous studies | |||
| Nonelite Australian football, Victoria, Australia29 | 1997–1998 | 24 / 1000 h | Common |
| Nonelite netball, Victoria, Australia30 | 1997–1998 | 12 / 1000 h | Common |
| Junior Australian football, Australia31 | 2004 | 18 / 1000 h | Common |
| Rugby, Australian football in Australian children32 | 2001 | 2.18 / 1000 h | Uncommon |
| Wheeled activities in Australian children32 | 2001 | 1.72 / 1000 h | Uncommon |
| Tennis in Australian children32 | 2001 | 1.19 / 1000 h | Uncommon |
| Trampoline use in US children 0–4 y28 b | 2009 | 0.70 / 1000 h | Rare |
| Trampoline use in US children 5–14 y28 b | 2009 | 1.60 / 1000 h | Uncommon |
| Study Period | Injury Rate | Incidence Descriptora | |
|---|---|---|---|
| Current study | |||
| Trampoline parks – any (all) injury | 2017–2019 | 1.14 / 1000 h | Uncommon |
| Trampoline parks – significant injury | 2017–2019 | 0.11 / 1000 h | Rare |
| Previous studies | |||
| Nonelite Australian football, Victoria, Australia29 | 1997–1998 | 24 / 1000 h | Common |
| Nonelite netball, Victoria, Australia30 | 1997–1998 | 12 / 1000 h | Common |
| Junior Australian football, Australia31 | 2004 | 18 / 1000 h | Common |
| Rugby, Australian football in Australian children32 | 2001 | 2.18 / 1000 h | Uncommon |
| Wheeled activities in Australian children32 | 2001 | 1.72 / 1000 h | Uncommon |
| Tennis in Australian children32 | 2001 | 1.19 / 1000 h | Uncommon |
| Trampoline use in US children 0–4 y28 b | 2009 | 0.70 / 1000 h | Rare |
| Trampoline use in US children 5–14 y28 b | 2009 | 1.60 / 1000 h | Uncommon |
Incidence descriptors as per Council for International Organizations of Medical Sciences20 : very common, ≥1 of 10; common, ≥1 of 100 and <1 of 10; uncommon, ≥1 of 1000 and <1 of 100; rare, ≥1 of 10 000 and <1 of 1000; very rare: <1 of 10000.
Incidence derived from US Consumer Product Safety Commission’s National Electronic Injury Surveillance System.28
The findings of this study do not detract from the importance of taking the necessary steps to reduce rates of trampoline park injury, especially severe injury. The ATPA-compliant operators participating in this study already employ various safety measures, including safety or grip socks, customer advice on entry, posters and announcements alerting jumpers to dangers, supervision, and first aid training for park staff. In addition, a new Australian Standard (AS 5159.1:2018) was launched in October 2018, stipulating the minimum safety requirements for trampoline parks operating in Australia.36 This is not currently a mandatory Australian Standard for trampoline park design and operation, albeit all 3 operators involved in this study were early adherents to the Standard.37 Both in Australia and internationally, safety-focused standards are seen by injury prevention and industry commentators as an essential and effective vehicle to improve safety and reduce injuries, especially for children.8,38,39 It is noted that the rate of significant trampoline park injuries in this study declined sharply in the months after launch of the Australian Standard (AS 5159.1:2018). Indeed, operator-specific time trend analyses show rates of trampoline park injury already declining in the months before the launch, at a time of significant media attention and public health discourse in anticipation of these new standards.37,40 This study was unable to determine whether the new Australian Standard, existing ATPA and IAPT standards, other operator-employed safety measures, or park user practices directly impacted rates of trampoline park injuries, and this remains a question for future research.
This study has limitations, most notably the lack of cross-checking of operator-provided data (eg, against ambulance or hospitalization data). As a result, injuries may be miscounted and/or misclassified with respect to severity, skewing the estimate of harm relative to exposure (jumper hours). Future studies should include data validation and linkage to better understand short and long-term outcomes of trampoline park injuries. Another limitation relates to assumptions made about the proportion of time users spend on various park activities. These assumptions could be mitigated with additional data detailing users’ movement through the park and time on each activity. Exposure data could also be improved by gathering demographic and ticket time-stamping data for all park users, rather than only those injured. This would enhance the design, assessment, and impact of injury surveillance and prevention initiatives. This study also identified prospective targets for preventing injuries of specific severities. We recommend leveraging such insights with future in-depth analysis of how, why, when, and for whom trampoline park injuries occur, especially severe injuries. This could involve video audit, which is feasible given many parks have existing closed-circuit television infrastructure as a quality and safety measure. Finally, we investigated injuries within safety standard-compliant trampoline parks. Therefore, the injury rates and time trends reported in this study may not be representative of trampoline parks who do not comply with such safety standards, eg, minimum supervision ratios, equipment materials, and engineering specifications. This is an important caveat with public health messaging implications for this and future studies. At present, only half of all Australian trampoline parks operate in full compliance with ATPA and Australian standards. Users of noncompliant parks may face higher injury risks, and injury prevention advocates advise consumers to specifically seek out trampoline parks that comply with industry and national safety standards.8,37,40
Conclusions
This study provides robust exposure-adjusted injury rates for trampoline park injuries, demonstrating these injuries to be uncommon and rare events, the rates of which are declining over time in these safety standard-compliant trampoline parks. These findings positively reframe and refocus the narrative of injury prevention toward engagement of health, trampoline park operators and users toward a shared goal of preventing injuries, especially severe injuries. This study provides multiple targets for injury prevention, future research, and public health initiatives aimed at promoting safe and healthy use of trampoline parks.
Acknowlegdgements
We thank the staff of BOUNCEinc (Australia), BOUNCEinc (Middle East), and Sky Zone (Australia) who provided the data used in this study.
Dr Teague conceptualized and designed the study, coordinated and supervised the project and data collection, assisted with data curation and analysis, and drafted the initial manuscript; Drs Dipnall and Palmer each contributed to design of the study, curated data, and designed and performed the analyses; and Dr Ben Beck contributed to design of the study, coordinated and supervised the data curation and analysis, and assisted with drafting the initial manuscript; and all authors critically reviewed and revised the manuscript, approved the final manuscript as submitted, and agree to be accountable for all aspects of the work.
FUNDING: No specific funding was secured for this study. A/Prof Warwick Teague and A/Prof Ben Beck were recipients of general funding for their academic work: A/Prof Warwick Teague was supported by the Royal Children’s Hospital Foundation; A/Prof Ben Beck was supported by an Australian Research Council Future Fellowship (FT210100183).
CONFLICT OF INTEREST DISCLOSURES: The authors have no example conflicts of interest to disclose, including no current or prior relationships with the trampoline park operators providing injury and ticket sales data for this study.
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