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The engineering research on circus practice has been minimal. This study measured the peak cable tension for nine circus disciplines, including aerial hooping, rope, aerial Silk, flying poles, tightwires, Chinese poles, swinging trapezes, and solo or duo fixed trapezes. The cables in these disciplines were equipped with load cells, and tension force was recorded. Thirty-four acrobats from professional circus schools, as well as professionals and students, participated in this study. They performed 118 acrobatic moves. ANOVA (analysis of variance) was used to determine differences between participants. The statistical significance of participant differences was evident in almost all disciplines and movements. The maximum forces in aerial trapeze were 5.6 BW, 4.8 BW, 7.3 BW, 4.0 BW, flying pole and swinging trapeze. These findings could significantly impact acrobatic design, rigging, and circus equipment safety.
La pratique du cirque est une activite tres populaire pour laquelle peu de recherches en ingenierie ont ete publiees. L’objectif de cette etude etait de mesurer la tension maximale des cables dans neuf disciplines de cirque: cerceau aerien, corde lisse, tissu aerien, mat pendulaire, fil de fer, mat chinois, trapeze ballant, trapeze fixe solo et duo. Les cables de ces disciplines ont ete instrumentes avec des cellules de charge et la tension a ete enregistree. Trente-quatre acrobates, professionnels et eleves d’ecoles de cirque professionnelles, ont participe a l’etude et ont execute un total de 118 mouvements acrobatiques. Une analyse de la variance (ANOVA) a determine les differences entre participants. Presque tous les mouvements et disciplines ont montre une difference statistiquement significative entre les participants. Les forces maximales ont ete trouvees a 4.8 poids corporel en cerceau aerien, 7.3 fois le poids du corps en corde lisse, 5.6 fois le poids du corps en tissu aerien, 4.0 fois le poids du corps en mat pendulaire, 5.6 fois le poids du corps en trapeze ballant, 6.8 fois le poids du corps en trapeze fixe solo et 2.5 fois le poids du corps en trapeze fixe duo, et la tension maximale dans le cable a ete trouvee a 15 kN dans le fil de fer et 2.8 kN dans le mat chinois. Ces resultats peuvent avoir des implications importantes pour la conception et le greage acrobatique afin d’ameliorer la securite des equipements de cirque.
The following is a brief introduction to the topic:
In Quebec, En Piste (an organization that brings together professionals in circus arts and organizations) counts more than 100 circus enterprises in 2020. These include companies, schools, social-circus organizations, and event diffusers.
Cirque injury rates and patterns have been studied among professional circus artists,3-6, student artists7-9, and adolescents.10 Several longitudinal studies focused specifically on Cirque du Soir, four on the National Institute of Circus Arts, seven on the National Center for Circus Arts, and eight on the Montreal Circus School.9 While definitions of injuries are inconsistent, the equipment is mentioned as a factor of external injury.6,8,11
Safety standards for entertainment technology, such as ANSI E1.43:2016, guide performing flying systems’ design, manufacture, use, and maintenance. The American ANSI e1.43:2016 standard for entertainment technology refers to the design, manufacture, and use of performer-flying systems. 15 Although the standard is often used for rigging, it excludes “any connections that rely on the strength or abilities of the Flying Performer” 16, as with most circus equipment. The standard, for example, sets minimum design criteria related to the working loads limit (WLL), characteristic load, and peak load. The WLL can be described as the “maximum weight that the Flying System Designer allows a user to apply to a lift medium in the performer’s flying system.” 14 The characteristic load and peak load represent the maximum forces on the system due to normal and abnormal usage. Circus professionals cannot calculate the target because they do not have data on the peak or characteristic loads. The rigging hardware for the circus can be obtained from various industries, including climbing, entertainment, or industrial rigging. It is essential that if equipment designed for one of these activities will be used for circus practice, the circus professional ensures that the rigging meets the mechanical requirements to ensure the safety and security of the performers.
There are no standard values for the dynamic factor, so that it can vary from 3-10 depending on the practice. The design factor can also be called “factor of security” or “safety.” The safety factor is applied to the dynamic force when designing equipment.
Riggers and designers of circuses need to know the forces applied to equipment to ensure it is strong enough to handle the acrobatics. Few studies have examined the influences that circus acrobats apply to their equipment. In a prior study, we measured the dynamic forces applied by circus acrobats to five aerial apparatuses. 15 The results of this study led us to make safety and design suggestions to improve circus practice and optimize equipment. The circus disciplines are diverse and do not only include these five aerial apparatuses. Therefore, more data is needed. Literature has covered fields like rings in gymnastics23, slackline24, and vertical jumps by acrobats25, but various circus disciplines still require investigation. The present study aimed to (1) assess the maximum forces generated by circus performers for different acrobatic movements in nine circus disciplines: aerial hooping, rope, aerial Silk, flying poles, tightwires, Chinese poles, swinging trapezes, as well as duo and solo fixed trapeze.
The study involved 34 acrobats (11 students and 23 professionals with a combined experience of 9.1 +-4.5 years and 9.1 ++ 4.5 years) from nine different circus disciplines. The National Circus School of Montreal and Polytechnique Montreal’s ethical research committee approved the project. The number of acrobats was as follows by field: five in aerial hoops, five on rope, two Silk, two flying poles, four tightwires, five Chinese poles, four (solos) swinging trapezes, three solos fixed trapezes and two duos (4-acrobats each) fixed trapezes.
The tests were conducted at the National Circus School in Montreal. Appendix 1 contains a detailed list of circus equipment. Figure 1. shows the specific dimensions and locations of load cells. The three different types of load cells (LSB350-1,050 pounds (lbs), LC455-2,050 lbs, and LSB400-10,050 lbs, Futek, Irvine US) were connected to a data acquisition chassis by National Instruments (cDAQ-9184 & cDAQ-99191, Austin, Texas US). A VPN router DSR-250 (D-Link Canada) connected the Basler IP cameras (Basler BIP2-1920c, National Instruments Austin, Texas, US) and the load cells to the computer G750JS (Asus). LabVIEW 2015 (National Instruments) was used to save the force data and the video files on the computer. All load cells were sampled at 2,000 hertz. A second tripod-mounted camera captured the wide shot. The setup for single-point aerial disciplines (aerial Silk, aerial rope, aerial hoop, and flying poles) was similar to our previous study 15, except that the emitter has been replaced by a Wi-Fi chassis cDAQ-9191, connected to the router. The load calibration certificates supplied by the supplier showed the sensitivity values for all eight cells (4 LCF455, three LSB350, and one LSB400). Manual calibration was used to adjust the load cell sensitivity before the test. This involved two masses calibrated at 45.4 kg each and weighted additional disks for 295.6 kilograms.
All measurements were made under the same experimental conditions, including equipment, rigging points, and starting heights (in aerial Silk or aerial rope). Participants performed their routine for 10 to 20 minutes before data collection. Acrobats repeated four figures four to six times. Coaches from the circus school selected the figures in advance, with two instructions. The chosen figures should be classic or standard and generate high loads. Circus acrobats wanted to give a unique performance, and so, even though traditional figures were chosen, they aimed for an unstandardized technique. Some statistics were performed by only some acrobats of the same discipline. Acrobats also performed additional acrobatic moves that they selected once or twice. This was to determine if the figures were generating high loads. The participants could rest as long as they needed between each sculpture. Participants wore the clothes and accessories required by their discipline, i.e., custom-made shoes in tightwire with flexible and thin leather insoles, long sleeves in Chinese poles, flying poles, and gaiters for swinging trapeze. The data analysis did not include missed repetitions. A total of 673 data sets for 118 acrobatics figures were collected.
Preload values were also included in the measurement in the case of the Chinese pole and tightwire setups. The circus equipment weight for the other forms was not included in the force measurements as the load cell was tared after the design. The equivalent vertical force was calculated using a test protocol, and the body weight (BW) was to be expressed as the tension force on the cable of the tightwire ( Appendix 2).
Data were analyzed with the help of a MATLAB script (MATLAB R2019a software; The MathWorks Inc., Natick, Massachusetts, US). Data were analyzed using a MATLAB program (MATLAB R2019a; The MathWorks Inc. Natick, Massachusetts). In the three trapeze disciplines, force data from both cables were added. In all fields, except the Chinese pole, the maximum force was calculated for each trial and expressed in BW based on the weight of the acrobat. In a duo-fixed trapeze, the staff was normalized by adding the mass of both acrobats. Due to the configuration, it was not possible to calculate the forces of the three cables on the Chinese pole in BW.
A one-way analysis was performed to compare the differences between participants performing the same movements to compare maximum forces. For each activity, the statistical analysis was conducted with at least three participants that completed each exercise four times. We retained six tightwire movements, five Chinese pole movements, three aerial hoop movements, and one rope movement. The Tukey test, used as a posthoc analysis when differences were found, was used to determine specific participant differences. Bonferroni corrected the significance criteria as p0.05/ n, where n represents the number of movements for each discipline. For the Chinese pole, the significance level was p0.0025 because we performed twenty analyses. The Shapiro-Wilk test was used to verify the normal distribution. All studies were carried out with R 27 and all graphs using MATLAB.
The maximum force in the tightwire was 65% higher than the pretension load. In the Chinese pole discipline, a 125% increase was seen in the load cell beneath the pole and a 58%, 72%, and 47% increase in cables 1, 2, and 3.