**1. Introduction**

The importance of participating in su fficient physical activity (PA) in childhood and adolescence and the benefits of PA on physical health, mental health, academic performance, and social well-being have been well proven [1–5]. However, the decrease in participation in PA in adolescence is recognized as a global problem, which is additionally important since a decrease in PA may extend into adult life [6–8]. Despite the fact that Slovenian children and adolescents are among the most physically active in the world, their levels of PA have decreased in recent years, and this problem is especially exacerbated during adolescence [9].

To prevent a decrease in PA, various interventional programs have been constructed to encourage children and adolescents to be more physically active [10,11]. Since such programs should be motivational and attractive, dance is a perfect tool, as it fulfils not only PA requirements but also enables the development of social skills and expressiveness in youth [12–14]. As some individuals begin to dance very early in their childhood, dance is a particularly suitable form of PA that can be continuously applied whether in a professional or recreational context, throughout a participant's lifetime [15–17].

However, as with any other PA, dance participation is accompanied by a certain risk of injury, even in youth [17–19]. Studies have reported that 20–84% of dancers have su ffered from a musculoskeletal (MS) injury at least once in their career, and an even higher percentage (95%) have su ffered from MS pain [18,20,21]. MS injuries vary by dance style, and by far the most common dancers to experience MS injuries are ballet dancers, followed by urban dancers (i.e., breakdance, hip-hop, locking, popping, house) and modern dancers [16,22,23].

Collectively, studies have confirmed higher injury rates in older dancers and/or shown a correlation between a dancer's age and the occurrence of injury [24]. Further, due to characteristics of the dance activity and specifics of artistic expression, anthropometric/body build indices are known to be associated with injury risk, with a higher risk of injury in dancers with longer body segments and more body fat [25]. Studies have also confirmed that a there is a higher risk for injury occurrence in female dancers than in their male peers, which is connected to the most commonly injured body location in dancers (the knee), whereby the larger Q-angle in females potentially translates into greater forces of the quadriceps being applied to the patella and encourages mal-tracking [26,27]. Finally, a recent study provided evidence of a possible influence of dynamic balance as a protective factor against injury occurrence in dance, which was explained by the connection between dynamic balance and a dancer's ability to sustain equilibrium by keeping their body over its base of support [17,28].

Irrespective of the well proven benefits of dance and the risks of participation in dance, only a few studies have exclusively examined youth dancers with regard to injury prevalence and factors of influence. In brief, US authors examined adolescent dancers (avg. age 15.3 y) at a liberal arts high school dance program over a one-year period (school year). Dancers self-reported 112 injuries (avg. 2.8 of self-reported injuries per dancer), and older age turned out to be the prevalent risk factor associated with self-reported injuries [24]. In a study of injury patterns in young, non-professional dancers, advanced age and increased exposure to dance (i.e., age) were also proven to be correlated with an increased prevalence of injury in girls (age 8–16 y) [29]. Meanwhile, there is an evident lack of studies that have prospectively examined factors associated with injury occurrence in youth dancers involved in di fferent dance styles.

Therefore, the aim of this study was to prospectively analyze the injury occurrence in adolescent dancers involved in di fferent dance styles (urban dance, standard/Latin dance, rock and roll) and to evaluate the possible factors influencing the occurrence of MS problems and injuries. Specifically, based on results of previous studies on di fferent dance styles, we were particularly interested in anthropometric/body build indices, sociodemographic and dance factors, and dynamic balance as factors of possible influence on injury status in adolescent dancers. We hypothesized that the studied factors significantly influence the injury status of adolescent dancers.

### **2. Materials and Methods**

### *2.1. Participants and Design*

A total of 126 young dancers (21 males) involved in urban dance (breakdance, hip-hop, locking, popping, house; *n* = 99), rock and roll (*n* = 14), and standard and Latin-American dance (*n* = 13) all aged 11–18 years (mean age 15.66 ± 1.57) from Slovenia participated in the present study. Participants were selected on the basis of their status in dance sport, and all participants should be regular competitors at national and international levels under the auspices of the Slovenian Dance Association (SDA) and the International Dance Organization at the study baseline. The participants had an average of 7.8 ± 2.78 years of dance experience and trained for 7.09 ± 4.56 h per week at their respective dance schools. Based on (i) a previously evidenced injury occurrence of 10% [17], (ii) a population sample

of 621 registered adolescent dancers in Slovenia for the studied year, (iii) margin of error of 0.05, and (iv) confidence level of 0.95, the required sample size for this investigation was calculated to be 114 participants (calculated by Statistica, Tibco Software Inc., Palo Alto, CA, USA)

In 2018, when the study was done, there were 23 dance teams/schools with registered adolescent dancers in Slovenia. All schools were invited to participate in the study by the SDA, and dancers were informed about the study's aims, protocol, potential benefits, and risks. The participants were asked to provide consent from their parents, and participation was voluntary and anonymous. Dancers were qualified for inclusion if they were (i) minors (18 years or younger at the end of the study—see later for design), (ii) o fficially registered as a competition participant in the International Dance Organization, and (iii) participating in at least two dance trainings per week. Exclusion criteria included age of 18+ at the end of the study, non-regular participation in dance training (less than two dance trainings per week as defined by main coach), and injury/sickness during the baseline testing (see later for details on testing). Participants willing to be enrolled in the study were invited to screening at the Institute of Sport (University of Ljubljana, Faculty of Sport, Ljubljana, Slovenia). Involvement in the research was voluntary, and participants' personal data were protected with an identification code, known only to the main/head researcher. The study protocol was approved by the Ethics Committee of the University of Ljubljana, Faculty of Sport, Ljubljana, Slovenia (Ref. number: 1175/2017). This prospective study included testing, which was done at baseline and during a follow-up period. Baseline testing of predictors (see later for details) was done in December 2018–January 2019, and follow-up testing was performed continuously over a period of 3 months after baseline and included an analysis of outcome.
