Injury Frequency and Characteristics in Adolescent and Adult Circus Artists
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Brief Report
Injury Frequency and Characteristics in
Adolescent and Adult Circus Artists
A Pilot Prospective Cohort Study
Stephanie Greenspan, DPT
BACKGROUND: Despite growing participation in circus ized injury surveillance guideline in circus, similar to the
arts, little is known about associated injuries. Understand- one used in this study, will provide greater insight into
ing injury patterns is critical for developing interventions injury patterns by allowing between-study comparison.
to decrease injury risk and guiding rehabilitation. OBJEC- Med Probl Perform Art 2021;36(2):103–107.
TIVE: The purpose of this pilot prospective cohort study
was to describe injury frequency and characteristics in CIRCUS ARTS participation in the United States (U.S.)
adolescent and adult circus artists using a surveillance grew rapidly from 2011 to 2018.1 Circus injury research2–5
method derived from dance. METHODS: Participants
included 14 adolescent [mean age 14.7 yrs (1.3); 100% has also expanded, but the depth and breadth doesn’t
female] and 10 adult circus artists [mean age 30.7 yrs compare to dance or gymnastics.6–11 Healthcare and circus
(3.1); 60% female]. Circus training exposure (single ses- professionals therefore rely on personal experience and
sion of one circus discipline) and injuries were tracked for non-circus research to guide injury prevention strategies
1 year using a dance-derived injury surveillance guideline. and rehabilitation for circus artists.
A regression analysis was run using total session expo-
sures, age (in years), and years of circus experience as Direct comparison of circus injury research is difficult
predictor variables for injury rate. RESULTS: Twenty-one because exposure and injury definitions are inconsistent,
of 24 participants completed the study. Forty-seven and study populations vary in age, skill level and circus
injuries were reported (53.2% time loss; 46.8% non-time disciplines.2–5 In a systematic review, Wolfenden5 identified
loss). Joint injuries were most common for both groups. between-study differences in injury definitions (time loss or
The injury rate per 1,000 exposures was 3 (95%CI 0.6–8.7)
for adolescents and 13 (95%CI 6.9–22.01) for adults. The medical attention), exposure measures (performances,
overall regression was significant (F(3,13)=6.66, p=0.006). hours, or athletic exposures), and participation level (recre-
The only significant predictor was age (beta=0.82, ational to professional). Similar variability in dance
p=0.003). Total session exposures and years of circus research prompted development of the International
experience had betas close to 0 (–0.11 and –0.04, respec- Association of Dance Medicine and Science (IADMS)
tively). CONCLUSION: This pilot study comparing injuries
in adolescent and adult circus artists found age but not Standard Consensus Initiative guideline12 which could
exposure was predictive of injury risk. Use of a standard- guide standardization of circus injury surveillance.
Circus injuries have not been compared in different age
Dr. Greenspan is Associate Professor, Department of Phys-
groups.2–5 Adolescents may have unique injury patterns
ical Therapy, Samuel Merritt University, Oakland, CA.
because of the mechanical properties of developing bone,
Presented in part at Education Session, American Circus cartilage, and muscle.13 This could explain why acute
Educators Conference, Oct 13, 2020; Platform Presenta- injuries are more common than overuse in adolescent
tion, Samuel Merritt University MARC Symposium, Oak-
artistic gymnasts.6,7 Artistic gymnastics and circus both
land, CA. Mar 7, 2020; Poster, American Physical Therapy
Association (APTA) Combined Sections Meeting, Denver, include ground and apparatus-based acrobatics. Higher
CO, Feb 13, 2020; and International Association of Dance levels of competition, more competition exposure, longer
Medicine & Science Annual Conference, Montreal, Canada, training duration, and increased age are all injury risk fac-
Oct 4, 2019. tors in artistic gymnasts.6 Female youth gymnasts have
Funding by a Samuel Merritt University Faculty Seed lower injury rates than female college gymnasts (8.5 vs
Grant. The author declares no conflicts of interest related 9.22/1,000 athletic exposures).7,8 We need to understand
to this study. how age influences circus injuries.
Address for correspondence: Stephanie Greenspan, Dep. of To reduce injury risk and improve rehabilitation for
Physical Therapy, Samuel Merritt University, 450 30th Street, circus artists, we need injury research with consistent
Ste 3730, Oakland, CA 94609, USA. Tel 510-879-9200 methodology allowing comparison. We also need to under-
x7346, fax 510-869-6282. sgreenspan@samuelmerritt.edu. stand how injury patterns differ by age. The purpose of
https://doi.org/10.21091/mppa.2021.2013 this pilot study was to describe injury frequency and char-
© 2021 by the Author. Open Access: Licensed under acteristics in adolescent and adult circus artists using a sur-
CC-BY-NC-SA-4.0 Int. veillance method derived from dance.
June 2021 103TABLE 1. Participant Characteristics by Age Group at Baseline
Adolescents (n=14) Adults (n=10)
Age (yrs) 14.7 (1.3; 13-17) 30.7 (3.1; 27-37)
Height (cm) 162.9 (7.5; 151.1-170.8) 169.1 (7.1; 152.4-169.6)
Mass (kg) 53.9 (6.3; 42.1-63.4) 64.5 (8.4; 53.3-76.9)
Circus experience (yrs) 5.1 (2.1; 1-9) 10.5 (4.9; 2-18)
Performances in last year (n) 17.36 (10.2; 2-35) 31.3 (51.8; 0-175)
Female sex (%) 100.0 60.0
Primary discipline aerial (%) 35.7 30.0
Primary discipline ground (%) 21.4 40.0
Primary discipline mixed (%) 42.9 20.0
Primary discipline Chinese pole (%) 0.0 10.0
Data given as mean (SD; range) for the top rows, and percentage of the group, adolescent or adult, for lower rows. One adult did not report performances on
her intake and therefore is excluded from that calculation. Aerial primary disciplines include silks, rope, trapeze, lyra, straps and sling. Primary ground disciplines
include hand-balancing, partner acrobatics, and contortion. Mixed refers to having a primary discipline in both ground and aerial categories.
METHODS Injuries unrelated to circus training and pre-existing
injuries were not tracked.
A prospective cohort study was conducted, adapting the
IADMS guidelines for a circus context.12 The guideline Injury Classification
recommends: 1) mandatory injury reporting, 2) time loss
(TL) and musculoskeletal complaint injury definitions, 3) Time loss injury (TL) was an “anatomic tissue-level impair-
injury classification by a healthcare professional, and 4) ment”12 that resulted in full loss of participation, in at least
one exposure defined as participation in a class, rehearsal one discipline, for 1 or more days from injury onset. Tissue
or performance.12 The Samuel Merritt University Internal impairments not meeting the criteria for TL were defined as
Review Board approved the study (SMUIRB#17-013). A non-time loss (NTL).12,14 New injury was in a body region and
convenience sample of circus artists that trained regularly of a nature that had not occurred within the last 2 months.
was recruited from a 24-member (22 F, 2 M) youth pre-pro- Recurrent injury was in the same body region, of the same
fessional training program and 55 (44 F, 11 M) adult nature, within 2 months of return to 100% participation
coaches employed at Kinetic Arts Center, a U.S circus after a TL injury.16 Overuse injury was related to repeated
training facility. Exclusion criteria included a planned exposure to a micro-trauma (e.g., movement, position, or
absence exceeding 1 month or lack of regular training. activity).10 Traumatic injury was related to a specific macro-
No medical staff or mandatory injury surveillance traumatic event (e.g., fall, awkward landing).10
system existed at the facility, so reporting was limited to
study participants. Participants were tracked for 1 year fol- Data Analysis
lowing their individual study enrollment date. The entire
study spanned September 2017 to December 2018. Enroll- Descriptive statistics were conducted using Microsoft
ment included a single visit for completion of an informed Excel 365 (ver. 2008; Redmond, WA) for participant char-
consent/parental consent/adolescent assent forms, acteristics, exposures, injury frequency, incidence and
intake questionnaire, and physical examination that inte- types. The relationship between exposure by time and ses-
grated elements of the Dance USA14 and National Insti- sions was described using a scatterplot. Remaining analy-
tute of Circus Arts screening guidelines.15 ses were done using IBM SPSS Statistics (ver. 25, IBM-
The intake included questions about age, gender, SPSS, Armonk, NY). Injury rate was calculated per 1,000
training experience, and medical/injury history. The session exposures.17 A regression analysis was run using
author, a licensed physical therapist, conducted the base- total training sessions, age (in years), and years of circus
line physical exams which included height, weight, and experience as predictor variables for injury rate. Signifi-
other physical examination measures beyond the scope cance level was set at 0.05.
of this brief report. Participants were emailed a training
log link (Qualtrics ver. 9/2017-12/2018, Provo, UT) RESULTS
each week for 1 year after enrollment. They reported
exposure as total time and sessions (classes, rehearsals, Of 79 potential participants, 24 enrolled (14 adolescents;
performances, or self-directed training) per circus disci- 10 adults) in and 21 completed the study. One adult
pline, any injuries, and missed training sessions due to dropped out due to illness, 1 adolescent due to leaving the
injury each week. For new or recurrent injuries, the training program, and another due to lack of tracking her
author conducted an assessment to determine the associ- training, after 8, 14, and 36 weeks, respectively. Their data
ated circus discipline, body region, tissue, and nature of were included in the analysis for the duration of their par-
the injury. Treatment was not included in the study. ticipation. Participant characteristics at baseline are
104 Medical Problems of Performing ArtistsTABLE 2. Injury Frequency and Type TABLE 3. Total and Weekly Exposure
Adolescents Adults Adolescents (n=12) Adults (n=9)
Total injuries 9 38 Total sessions/participant
All types 406.3 (147.9) 695.9 (256.8)
Non-time loss 5 (56%) 17 (45%)
Performances 51 (40.1) 109.6 (78.0)
Time loss 4 (44%) 21 (55%)
Training 355 (129.9) 586.3 (215.8)
Overuse 4 (44%) 21 (55%) Weekly sessions/participant
Traumatic 5 (56%) 17 (45%) All types 7.8 (2.8) 13.4 (4.9)
Site of injury Performances 1.0 (0.8) 2.1 (1.5)
Lower extremity 4 (44%) 12 (32%) Training 6.8 (2.5) 11.3 (4.2)
Upper extremity 3 (33%) 17 (45%) Sessions reported as mean (SD) for each group. Sessions were recorded by
Spine/head 2 (22%) 9 (24%) individual discipline (eg, if a participant has 1 rehearsal that included hand-
Tissue injured balancing and trapeze, it was counted as 1 rehearsal session for each disci-
pline). This information excludes the 3 participants who dropped out of the
Bone 1 (11%) 2 (5%)
study.
CNS 1 (11%) 0
Integument 0 1 (3%)
Joint 5 (56%) 18 (47%)
Analysis of the relationship between time and sessions
Muscle/tendon 2 (22%) 10 (26%)
Nerve 0 (0%) 7 (18%) (Figure 1) shows close to a 1:1 relationship except 4 adults
over 5 weeks of a show run.
Activity
Stretching 0 2 (5%) The injury rate per 1,000 session exposures was 3
Contortion 2 (22%) 2 (5%) (95%CI 0.6–8.7) for adolescents and 13 (95%CI 6.9–22.0) for
Hand balancing 0 5 (13%) adults. TL injury rates were 1.3 and 7.2. Adults’ average
Partner acrobatics 0 6 (16%) weekly and total exposure for both training and perform-
Tumbling 3 (33%) 3 (8%) ances was higher (Table 3). The regression analysis using
Trampoline 0 1 (3%)
Dance 0 3 (8%) exposure, age and experience as predictor variables was
Rope 0 5 (13%) significant (F(3,13)=6.66, p=0.006). The only significant pre-
Silks 0 4 (11%) dictor was age (beta=0.82, p=0.003). Total sessions and
Straps 1 (11%) 0 years of circus experience had betas close to 0 (–0.11, and
Trapeze 1 (11%) 1 (3%) –0.04, respectively).
Chinese pole 0 4 (11%)
Aerial bar apparatus 1 (11%) 1 (3%)
Trip on mats 0 1 (3%)
DISCUSSION
Pulling lines 1 (11%) 0
This is the first study to compare injuries in adolescent and
Data given as n (%). adult circus artists. Total/time loss injury rates were 3/1.3
and 13/7.2 for adolescents and adults, respectively, per
1,000 exposures or sessions of a single circus discipline, or
shown in Table 1. Adults averaged 15 years older than
4.3–5.5 times higher in adults. TL injury rates were less
adolescents with only 5 more years of experience.
than those found in female youth and collegiate gymnasts
Injury Rates and Patterns (8.5 and 9.22/1,000 athletic exposures).7,8 This finding was
consistent with other circus research.2,4,5 Direct compari-
Forty-seven total injuries occurred (53.2% TL, 46.8% NTL), son of injury rates in circus research is difficult because of
including 3 recurrent injuries in adults. Table 2 shows the the different injury and exposure definitions.2–5
frequency of injury types. The mean duration of TL was Chronological age, but not prior experience or total ses-
32 (41 SD) days with range 1 to 185. Excluding dropouts, sion exposure, was a significant predictor (beta=0.82,
mean incidence of new injuries over one year in adoles- p=0.003) of injury. Growth and maturation13 was not
cents was 0.8 (0.8; 95% confidence interval [CI] 0.3–1.1) and accounted for, which could have affected this result. Skill
in adults 3.8 (1.0; 95%CI 3.1–4.4). Low incidence in adoles- level could be another variable in this outcome as most of
cents limited analysis by injury type. Of note, the only con- the adults (9/10) and only a few adolescents (2/14) per-
cussion was in an adolescent, and only adults reported formed at a professional level. Higher levels of competition
nerve or integumentary injuries. and more exposure to competition are injury risk factors in
For the first 13 weeks, participants tracked sessions and artistic gymnasts.6 Exposures to performance, which were
time. Participants found calculating time by discipline con- higher in the adults, may affect risk similarly to competi-
fusing and more demanding, affecting adherence. To assess tion. Injury patterns for adolescents and adults should be
accuracy, the author measured time per discipline in a per- investigated in a larger cohort with stratification by adoles-
formance with 4 study participants and compared it to par- cent development, skill level and performance exposure.
ticipants’ reports. Participants reports exceeded actual This study was the first to adapt the IADMS consensus
time. Due to these issues only sessions were tracked for the guideline12 to circus. Mandatory reporting was recom-
remainder of the study and used to calculate exposure. mended but few circus schools in the U.S. have medical
June 2021 105FIGURE 1. Comparison of measures of exposure. Each point on this scatterplot represents a single participant for a single
week. This spans week 1 (n=4) to week 13 (n=23) of the study period while time was being measured. The number of par-
ticipants increased over the consecutive weeks as enrollment increased. The outliers were 4 adult participants over 5
weeks that performed multiple disciplines in a single show.
staff or mandatory injury reporting. Injury surveillance sions was well correlated (Figure 1) except for a few out-
was therefore based on voluntary study participation. liers. Eliminating time tracking enhanced participant
Selection bias is possible with a 30.4% participation rate. adherence and satisfaction. Tracking exposure by disci-
The study duration, travel restriction and lack of an incen- pline is important to understanding injury mechanisms
tive were factors in enrollment. There were few male par- related to individual circus disciplines and tracking expo-
ticipants but sex distribution was reflective of the cohort sure by sessions is a feasible way to do so.
studied. The small sample size and possible selection bias
limits the generalizability of the results. Future studies Conclusion
should include a broader study population by age, gender,
skill level, and geographic areas to more accurately reflect In this first pilot study comparing injuries in adolescent
the U.S. circus population. and adult circus artists, exposure was higher in adults, but
On-site injury assessments facilitated adherence and age and not exposure predicted injury risk. Adapting the
likely contributed to the low attrition rate (12.5%). Health- IADMS guidelines for circus presented some challenges
care professional assessment provides more accurate data but may provide an effective framework to standardize
on injury type and mechanism than self-report.4,12 The circus injury research. This will allow comparison between
study investigator, an experienced physical therapist, was studies and facilitate better insight into circus injuries.
able to assess all injuries but there is a risk of potential bias Acknowledgments: The author thanks Kinetic Arts Center for part-
from this dual role. If study evaluators are employed by the nering in this research; Mary E. McCall for her assistance with statis-
artists’ school or company, some artists may avoid report- tical analysis; and Sarah Tiffin for data organization.
ing injuries over concerns about participation restrictions.
Open Access: This article is distributed in accordance with the Cre-
This was not a conflict in this study, but the cost or logistics ative Commons Attribution Non-Commercial No-Derivatives Share-
of having an independent assessor might be a barrier in Alike 4.0 International license (CC BY-NC-SA 4.0 Int.), which per-
larger studies. Nearly half of the injuries in this study would mits others to adapt and/or distribute this work provided the original
have been missed if only TL injuries were included. Includ- work is properly cited, appropriate credit is given, the use is non-com-
mercial, and the users makes their work available under the same
ing NTL injuries provides a broader understanding of
license. See: https://creativecommons.org/licenses/by-nc-sa/4.0/.
minor injuries, which may precede more serious injuries.3
The IADMS consensus guideline authors conclude that
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