Differences in Achilles tendon mechanical properties between professional ballet dancers and collegiate athletes utilizing shear wave elastography.

PURPOSE: To report normative stiffness parameters obtained using shear wave elastography in dorsiflexion from the Achilles tendons in asymptomatic professional ballet dancers and compare them with college-level athletes. METHODS: An Institutional Review Board (IRB)-approved study consists of 28 professional ballet dancers and 64 asymptomatic collegiate athletes. The athletes were further subdivided into runner and non-runner disciplines. Shear wave elastography (SWE) measurements were made in maximum ankle dorsiflexion position. RESULTS AND DISCUSSION: Forty-eight (52%) males and 44 (48%) females were examined with an overall mean age of 22.2 (± 3.8 years). There were no significant SWE differences between dominant and non-dominant legs in both groups and comparing spin vs. non-spin leg of ballet dancers (p > 0.05). Ballet dancers had significantly higher short-axis velocity values than runners and non-runners (2.34 m/s increase and 2.79 m/s increase, respectively, p < 0.001). Long-axis velocity was significantly higher in ballet dancers compared to non-runners (by 0.80 m/s, p < 0.001), but was not different between ballet dancers and runners (p > 0.05). Short-axis modulus was significantly higher in dancers compared to runners and non-runners (by 135.2 kPa and 159.2 kPa, respectively, p < 0.001). Long-axis modulus (LAM) was not significantly different in ballet dancers when compared to runners. CONCLUSION: Asymptomatic professional ballet dancers exhibit greater short-axis tendon stiffness compared to athletes and greater long-axis tendon stiffness compared to non-runners but similar to runners. The functional benefit from elevated short-axis stiffness in dancers is not clear but may be related to greater axial loading and adaptations of the tendon matrix.

Balletic bodies under lockdown: The consequences of a pandemic for highly disciplined habitus.

Like other elite athletes, ballet dancers are highly dedicated to the pursuit of their vocation. They work to perfect their bodies, their movements and their expression of the art form. The lockdowns that occurred during the COVID-19 pandemic represented a significant interruption to the extraordinary but everyday lives of ballet dancers, creating unique environments where exploration of the embodied habitus of ballet can be further investigated. The impacts of lockdown upon dancers were explored via a series of interviews with 12 professional dancers from Germany. Framed by previous research, theorising the balletic body from a Bourdieusian perspective, interview data were analysed using Interpretative Phenomenological Analysis. Our research highlights the way in which COVID-19 lockdowns and associated restrictions disrupt the habitus of dancers and results in a form of suffering that is comparable to injury or chronic illness. Our research suggests that individuals respond to the 'structural injuries' of lockdown measures in a manner comparable to the way they respond to physiological injury. Thus, dancers sought to repair or re-establish the social structures they ordinarily inhabit whilst the inevitable limitations of such efforts engendered occasions for reflexive thinking about their role, careers and identity as dancers.

Dancers with non-specific low back pain have less lumbar movement smoothness than healthy dancers.

BACKGROUND: Ballet is a highly technical and physically demanding dance form involving extensive end-range lumbar movements and emphasizing movement smoothness and gracefulness. A high prevalence of non-specific low back pain (LBP) is found in ballet dancers, which may lead to poor controlled movement and possible pain occurrence and reoccurrence. The power spectral entropy of time-series acceleration is a useful indicator of random uncertainty information, and a lower value indicates a greater smoothness or regularity. The current study thus applied a power spectral entropy method to analyze the movement smoothness in lumbar flexion and extension in healthy dancers and dancers with LBP, respectively. METHOD: A total of 40 female ballet dancers (23 in the LBP group and 17 in the control group) were recruited in the study. Repetitive end-range lumbar flexion and extension tasks were performed and the kinematic data were collected using a motion capture system. The power spectral entropy of the time-series acceleration of the lumbar movements was calculated in the anterior-posterior (AP), medial-lateral (ML), vertical (VT), and three-directional (3D) vectors. The entropy data were then used to conduct receiver operating characteristic curve analyses to evaluate the overall distinguishing performance and thus cutoff value, sensitivity, specificity, and area under the curve (AUC) were calculated. RESULTS: The power spectral entropy was significantly higher in the LBP group than the control group in the 3D vector in both lumbar flexion and lumber extension (flexion: p = 0.005; extension: p < 0.001). In lumbar extension, the AUC in the 3D vector was 0.807. In other words, the entropy provides an 80.7% probability of distinguishing between the two groups (i.e., LBP and control) correctly. The optimal cutoff entropy value was 0.5806 and yielded a sensitivity of 75% and specificity of 73.3%. In lumbar flexion, the AUC in the 3D vector was 0.777, and hence the entropy provided a probability of 77.7% of distinguishing between the two groups correctly. The optimal cutoff value was 0.5649 and yielded a sensitivity of 90% and a specificity of 73.3%. CONCLUSIONS: The LBP group showed significantly lower lumbar movement smoothness than the control group. The lumbar movement smoothness in the 3D vector had a high AUC and thus provided a high differentiating capacity between the two groups. It may therefore be potentially applied in clinical contexts to screen dancers with a high risk of LBP.

Body dissatisfaction, ideals, and identity in the development of disordered eating among adolescent ballet dancers.

OBJECTIVE: Little is known about how female adolescent ballet dancers-a group at high-risk for the development of body dissatisfaction and eating disorders-construct body ideals, and how their social identities interact with body ideals to confer risk for disordered eating. Using a novel body figure behavioral task, this study investigated (1) whether degree of body dissatisfaction corresponded to severity of disordered eating thoughts and behaviors, and (2) how ballet identity corresponded with ideal body figure size among adolescent ballet dancers. METHODS: Participants were 188 female ballet dancers ages 13-18 years who completed self-report measures of study constructs and the behavioral task. RESULTS: Linear regression models indicated that more severe body dissatisfaction was positively associated with increased disordered eating thoughts and behaviors (p < .19), except for muscle building (p = .32). We also found that identifying more strongly as a ballet dancer was correlated with having a smaller ideal body size (p = .017). CONCLUSION: Findings from this study suggest desire to achieve smaller body sizes is correlated with more severe disordered eating endorsement and stronger ballet identity. Instructors and clinicians may consider assessing the extent to which individuals identify as a ballet dancer as a risk factor for disordered eating and encourage adolescent dancers to build and nurture other identities beyond ballet. PUBLIC SIGNIFICANCE: Eating disorders are debilitating conditions that can lead to malnutrition, social isolation, and even premature death. Though disordered eating thoughts and behaviors can affect anyone, adolescents in physically demanding and body image-driven activities including ballet dance are particularly vulnerable. Investigating how factors like body dissatisfaction and strength of identity are associated with disordered eating among high-risk groups is crucial for developing effective prevention and intervention methods that minimize harm.

Graciousness, Elegance, and Firmness: Ballet and the Constitution of a Protective Environment for Peripheral Masculinities in Brazil.

Due to its graceful and light movements, its clothing, and body postures, ballet is tied to characteristics that are socially perceived as feminine. The aim of this paper is to describe the way men live and interact within the classic ballet environment, a way that is deemed deviant according to Western heteronormative norms of gender and sexuality. The overall idea was to delineate the masculinity that surrounds and is built in this space, and how ballet operates to build the identities of these individuals. The research was done through direct observation in a ballet school linked to one of the oldest and most important ballet institutions in Brazil. The main idea expressed is that ballet acts as a protective environment for young men who break out of heteronormativity. It is believed that men subvert social norms in this environment because that is where behaviors that escape hegemonic masculinity are more acceptable, gain representativeness and legitimacy.

VITAMIN D AND INJURIES IN DANCERS: A SYSTEMATIC REVIEW.

Vitamin D is involved in many different functions in the human body. Despite the well-known benefits of vitamin D and increasing trends of testing and supplementation, there is still a high prevalence of vitamin D deficiency worldwide, present in the general but also in the highly-active population such as athletes and dancers. Dancers are at a higher risk of vitamin D deficiency due to their long working hours spent indoors, without exposure to sunlight. The high level of workload and physical demands also put dancers at a high risk of injuries. The aim of this review was to systematically analyze the existing evidence on the association of vitamin D (serum level and supplementation) and injuries in dancers. Medline, Scopus, SportDiscus and Web of Science were searched to identify the available peer-reviewed articles. Five articles met the inclusion criteria (two interventional and three observational studies), three of which additionally investigated the relationship between vitamin D and muscle function. The reported results on positive influence of vitamin D serum level or vitamin D supplementation effect on reduced injury occurrence and enhanced muscular function in adolescent and elite professional ballet dancers are promising but the evidence is limited due to a low number of studies, small samples, and methodological limitations.

Ballet after breast cancer: investigating the feasibility and acceptability of a novel 16-week classical ballet intervention for breast cancer survivors.

PURPOSE: The "Ballet after breast cancer" study sought to investigate the feasibility and acceptability of a 16-week classical ballet intervention for breast cancer survivors, delivered face-to-face and/or online. METHODS: Breast cancer survivors were recruited to take part in 2 × 1-h ballet classes per week for 16 weeks. Primary outcomes of feasibility and acceptability were assessed according to rates of enrolment and attendance and participant feedback via questionnaire. Secondary outcomes included quality of life (QOL), upper-body disability, shoulder range of motion (ROM), muscular strength, aerobic capacity, and physical activity levels. Associations between rate of attendance and changes in secondary measures were explored. RESULTS: Thirty-one participants (62% of eligible individuals) enrolled in the program. Twenty-nine women commenced the intervention [53.3 ± 10.8 years (Mean ± SD)], attending 77.6% [67.6, 87.5] (Mean [95% CI]) of sessions. Based on these rates of enrolment and attendance, and participant feedback, the program was deemed feasible and acceptable to participants. Significant improvements in shoulder ROM and reductions in sedentary behaviour were achieved. Participants also reported improvements in physical capacity and psychological, social, and cognitive wellbeing. CONCLUSIONS: The "Ballet after breast cancer" program, delivered face-to-face and/or online, was feasible and acceptable to breast cancer survivors. Improvements in shoulder ROM achieved doing ballet were pertinent given the adverse effects of upper-body morbidity on breast cancer survivor QOL. Improvements in physical activity behaviour and perceived benefits to wellbeing also support the use of ballet to mitigate QOL impairment after treatment. IMPLICATIONS FOR CANCER SURVIVORS: The physical demands and the fun, creative, and social characteristics of ballet promote improvement across multiple domains of health and wellbeing. Ballet shows promise as an activity to improve QOL and increase long-term engagement in health-promoting physical activity after breast cancer.

Injury characteristics in professional modern dancers: A 15-year analysis of work-related injury rates and patterns.

We investigated work-related-musculoskeletal-injuries (WMSI) over 15-years in professional modern dancers to determine injury rate and pattern differences due to sex and professional-experience. Injuries were coded to allow analyses by tissue-type, body-region, severity, setting, mechanism, action-causation, and repertory-style. Injury prevalence (IP) was defined as average risk of injury/dancer. Injury incidence rate (IIR) was calculated per 1000-hrs exposure/block. Negative binomial logistic regression analyses were conducted with exposure-hrs to determine IIR, p < 0.05. Multinomial logistic regressions determined differences in tissue-type, body-region, action-causation and repertory-style; Poisson loglinear regressions determined differences in severity and mechanism, p < 0.05. Females were 15-times more likely to sustain bone-injuries, p = 0.016; males 8- and 15-times more likely to sustain muscle/tendon-injuries or lacerations/contusions, p ≤ 0.016. Females were more likely to sustain severe injury resulting in more lost-workdays and missed-performances, p < 0.001. In both sexes, more time-loss-injuries (TL-inj) occurred in performance , were traumatic in nature, with an action-causation of jumping/stomping/relevé. Dancers of moderate professional-experience were 1.3-times more likely to sustain TL-inj, p = 0.026;. Identifying context-specific activities and repertory-style relationships to injury can provide insight into casting and rehearsal scheduling. Comprehending sex-specific musculoskeletal health needs allows improved dancer health management and injury prevention planning.

Understanding hip pathology in ballet dancers.

PURPOSE: The literature on hip injuries in ballet dancers was systematically evaluated to answer (1) whether the prevalence of morphological abnormalities and pathology of hip injuries in dancers differs from the general population (2) if there are any specific risk factors which contribute to a higher rate of hip injury and (3) what are the outcomes of primary and secondary intervention strategies. METHODS: A systematic literature search of Medline, EMBASE and the Cochrane Library was undertaken for all literature relating to hip injuries in ballet dancers using the PRISMA guidelines. Reference lists were also searched for relevant literature. Clinical outcome studies, prospective/retrospective case series published between 1989 and October 2021 were included. Review articles (non-original data), case reports, studies on animals as well as book chapters were excluded. RESULTS: The search yielded 445 studies, of which 35 were included for final analyses after screening. This included 1655 participants, of which 1131 were females. The analyses revealed that damage at the chondrolabral junction and degenerative disease of the hip may develop at a higher rate in ballet dancers than in the general population (odds ratio > 1 in 15/18 cohorts). The intra-articular lesions were more frequently found in postero-superior region of the hip suggesting an alternative impingement mechanism. Furthermore, numerous risk factors specific for hip injury in ballet were highlighted amidst a wide body of literature which consistently reports risk factors for a more generic 'dancer vulnerability'. CONCLUSION: Ballet dancers may suffer from both higher rates of chondrolabral damage and degenerative disease in their hips. In contrast to other sports, the intra-articular lesions are more frequently found in postero-superior region of the hip. Future research clarifying the prevalence of osseous abnormalities and prevention strategies in dancers may be pivotal in delaying the development of hip disease in this cohort. LEVEL OF EVIDENCE: Level IV.

Eating psychopathology in ballet dancers: a meta-analysis of observational studies.

OBJECTIVE: To assess whether ballet dancers have higher eating psychopathology mean scores than the general population. METHODS: Meta-analysis of cross-sectional observational studies comparing the scores of one or more of the validated eating psychopathological scales between ballet dancers and any control groups. RESULTS: Twelve studies were included in the metanalysis. Ballet dancers had a significantly higher EAT score (12 studies retrieved, SMD 0.82 [95% CI 0.44-1.19], p < 0.00001, I2 = 84)]; subgroup analysis suggested a possible role of control subjects' choice in explaining heterogeneity. Scores on the EDI subscales of Drive for Thinness, Bulimia, and Body dissatisfaction were available from four studies; Drive for Thinness was higher in ballet dancers (SMD 0.62 [0.01, 1.22]), as well as the Bulimia scale (SMD 0.38 [0.02, 0.73], p = 0.04) and the Body Dissatisfaction scale (SMD 0.34 [0.15, 0.53]). Data on Perfectionism, Interpersonal problems, Ineffectiveness, and Maturity fears, were available from three studies. Higher scores in Perfectionism (SMD 0.68 [0.24, 1.12] p = 0.02), Interpersonal problems (SMD 0.24 [0.02, 0.47], in Inefficacy, (SMD 2.18 [1.31, 3.06]) were found for ballet dancers; on the other hand, Maturity fears scores were not significantly different between ballet dancers and controls (IV-MD = 0.15 [- 0.07, 0.36]). Seven studies reported tests not performed elsewhere. DISCUSSION: Ballet dancers show a higher level of restriction and drive for thinness than controls, and they may be, therefore, at higher risk for the development of eating disorders. Available studies do not allow the discrimination of dysfunctional eating attitudes and behaviors from adaptive responses. LEVEL OF EVIDENCE: Level I (evidence obtained from systematic reviews and meta-analyses).

Posterior Ankle Impingement Caused by Hyaline-Like Cartilage Generation in Ballet Dancers-A Report of 2 Cases.

Posterior ankle impingement syndrome is mainly seen in ballet dancers and frequently associated with specific movements in ballet such as pointe and demi pointe in which the whole-body weight is applied to the maximally plantar flexed ankle. We performed arthroscopic debridement for 2 dedicated ballet dancers on the intervening soft tissue causing posterior ankle impingement syndrome (PAIS). In both cases, T2-weighted magnetic resonance imaging (MRI) revealed low-signal intensity of meniscus-like soft tissue without abnormal osseous findings, connecting from the posterior side of the talus to Kager's fat pad. To examine the intervening soft tissue in detail, we performed histological evaluation by hematoxylin and eosin staining, Safranin O fast green staining, and immunohistochemistry for type I collagen and type II collagen. Hematoxylin and eosin staining showed that there was cartilage-like tissue including chondrocyte-like cells in contact with fibrous tissue. The extracellular matrix in the cartilage zone was consistently stained by Safranin O staining and type II collagen without any staining with type I collagen. These findings suggested that the meniscus-like soft tissue appearing as low-signal intensity on MRI at the posterior side of talus included hyaline-like cartilage. To the extent of our knowledge, these were rare cases of hyaline-like cartilage generation causing PAIS in ballet dancers, which might be associated with ballet specific movements resulting in chondrogenesis.

Plantar Venous Pump Activity, Generalized Joint Hypermobility, and Foot Mobility in Ballerinas: A Case-Control Study.

CONTEXT: The plantar venous pump (PVP) is a vascular network located between the muscles of the foot arch. It has been suggested foot mobility is critical for PVP activation. OBJECTIVE: This study investigates the effect of generalized joint hypermobility (GJH) on foot mobility and PVP activity in ballerinas and to determine how a short-term warm-up exercise impacts these parameters in the presence of GJH. DESIGN: Prospective study. METHODS: Twelve ballerinas (age = 16.73 [1.8] y) and 15 non-dancer-matched controls (age = 16.31 [2.1] y) were included. When performing weight-bearing activities, venous return parameters (diameter, velocity, and flow volume) from the posterior tibial vein were measured using color and spectral Doppler ultrasonography. Foot mobility was determined using navicular drop test. The participants performed a 10-minute cycling exercise to reveal its effect on reducing tissue stiffness. All measurements were performed synchronously and twice-before and after the cycling exercise. RESULTS: The results showed the navicular height obtained before and after exercise in the ballerinas was significantly different compared with that obtained in the sitting position, and the values obtained in the 3 measurement positions in the nondancer group were significantly different from each other (P < .05). The difference between the venous diameter values measured before and after exercise and the reference value was significant in both groups (P < .001). There was a significant decrease in venous velocity following exercise in the nondancer group (P = .044). The venous volume values obtained after exercise were significantly different between the groups (P = .039). CONCLUSIONS: The GJH has no distinctive effect on foot mobility and PVP activity in ballerinas. The presence of GJH did not influence the effect of short-term warm-up exercise on foot mobility and PVP activity. We believe that measuring the navicular drop and venous return with a more precise synchronization may provide additional information regarding the link between arch tension and venous return.

Within- and between-day loading response to ballet choreography.

Overuse pathologies are prevalent in ballet injury. Ten amateur ballet dancers (age: 23.20 ± 3.08 years) completed a progressive 5-stage choreographed routine on two consecutive days. Tri-axial accelerometers positioned at C7 and the dominant and non-dominant lower-limb were used to calculate accumulated PlayerLoadTM (PLTOTAL) and uni-axial contributions of the anterior-posterior (PLAP), medial-lateral (PLML), and vertical (PLV) planes. PLTOTAL increased significantly (p = 0.001) as a function of exercise duration within-trial, however there was no significant change between trials (p = 0.18). PLTOTAL at C7 was significantly (p = 0.001) lower than both lower-limbs, with no bilateral asymmetry evident (p = 0.97). Planar contributions to PLTOTAL were significantly greater in PLV than PLAP and PLML (p = 0.001). PlayerLoadTM demonstrated within-trial sensitivity to the progressive routine, however no residual fatigue effect was observed between trials. The results of this study suggest that accelerometers have efficacy in athlete monitoring and injury screening protocols, however unit placement should be considered for practical interpretation.

[Fabulus of the concert for the 100th anniversary of Yevdokimov Moscow State University of Medicine and Dentistry].

On the basis of critical analysis of sources the author reveals the role of doctors in opera productions, ballet and art in general. Looking through opera librettos and director's productions the author makes conclusions about characteristic human health problems, treatment methods used and the social status of doctors. About 10 percent of the four hundred opera and ballet productions performed today include doctor characters. These characters differ significantly from each other, depending on the time of creation of the work or the era reflected in the plot.

Magnetic resonance imaging findings associated with posterior ankle impingement syndrome are prevalent in elite ballet dancers and athletes.

OBJECTIVE: To report the prevalence of MRI features commonly associated with posterior ankle impingement syndrome in elite ballet dancers and athletes and to compare findings between groups. MATERIALS AND METHODS: Thirty-eight professional ballet dancers (47.4% women) were age- and sex-matched to 38 elite soccer or cricket fast bowler athletes. All participants were training, playing, and performing at full workload and underwent 3.0-T standardised magnetic resonance imaging of one ankle. De-identified images were assessed by one senior musculoskeletal radiologist for findings associated with posterior ankle impingement syndrome (os trigonum, Stieda process, posterior talocrural and subtalar joint effusion-synovitis, flexor hallucis longus tendon pathology and tenosynovitis, and posterior ankle bone marrow oedema). Imaging scoring reliability testing was performed. RESULTS: Posterior talocrural effusion-synovitis (90.8%) and subtalar joint effusion-synovitis (93.4%) were common in both groups, as well as the presence of either an os trigonum or Stieda process (61.8%). Athletes had a higher prevalence of either os trigonum or Stieda process than dancers (74%, 50% respectively, P = 0.03). Male athletes had a higher prevalence of either os trigonum or Stieda process than male dancers (90%, 50% respectively, P = 0.01), or female athletes (56%, P = 0.02). Posterior subtalar joint effusion-synovitis size was larger in dancers than athletes (P = 0.02). Male and female dancers had similar imaging findings. There was at least moderate interobserver and intraobserver agreement for most MRI findings. CONCLUSION: Imaging features associated with posterior impingement were prevalent in all groups. The high prevalence of os trigonum or Stieda process in male athletes suggests that this is a typical finding in this population.

T1rho and T2 mapping of ankle cartilage of female and male ballet dancers.

BACKGROUND: Since ballet dancers begin their training before skeletal maturity, accurate and non-invasive identification of cartilage diseases is clinically important. Angle-dependent analysis of T1rho and T2 sequences can be useful for quantification of the composition of cartilage. PURPOSE: To investigate the angle-dependent T1rho and T2 profiles of ankle cartilage in non-dancers and dancers. MATERIAL AND METHODS: Ten female non-dancers, ten female dancers, and 9 male dancers were evaluated using T1rho and T2 mapping sequences. Manual segmentation of talar and tibial cartilage on these images was performed by two radiologists. Inter- and intra-rater reliabilities were calculated using intraclass correlation coefficients (ICCs) and Bland-Altman analysis. Mean thickness and volume of cartilage were estimated. Angle-dependent relaxation time profiles of talar and tibial cartilage were created. RESULTS: ICCs of the number of segmented pixels were poor to excellent. Bland-Altman plots indicated that differences were associated with segment sizes. Segmented cartilage on T1rho demonstrated larger thickness and volume than those on T2 in all populations. Male dancers showed larger cartilage thickness and volume than female dancers and non-dancers. Each cartilage demonstrated angular-dependent T1rho and T2 profiles. Minimal T1rho and T2 values were observed at approximately 180°-200°; higher values were seen at the angle closer to the magic angle. Minimal T2 value of talar cartilage of dancers was larger than that of non-dancers. CONCLUSION: In this small cohort study, regional and sex variations of ankle cartilage T1rho and T2 values in dancers and non-dancers were demonstrated using an angle-dependent approach.

Experiences of delayed maturation in female vocational ballet students: An interpretative phenomenological analysis.

INTRODUCTION: There is a well-established bias toward late maturing females in the context of ballet, with up to 70% of professionals delayed in maturation. The timing of maturation has implications for physical and psychological outcomes which are likely to be amplified in dance. The aim of this research was to explore the role of maturity timing in adolescent dance students' experiences of vocational ballet training. METHODS: Semi-structured interviews were carried out with 28 adolescent female dancers of differing maturity timing across three vocational ballet schools in the UK. Interpretative phenomenological analysis was employed in the analysis of data. This study comprises findings from the nine late maturing dancers within the sample. RESULTS: Late maturing dancers perceived a number of aesthetic and functional advantages. The aesthetic advantages noted by the dancers are congruent with the well-established bias toward a later maturing physique for ballet; being 'small' and not having 'bits' is advantageous for these dancers in terms of maintaining a more pre-pubescent look and thereby conforming more easily to the expectations of the ballet world. However, dancers in this study perceived some significant drawbacks. Despite aesthetic advantages, later maturing dancers were disadvantaged by the current training system which sees them undertaking the most crucial training period during their most rapid period of growth. CONCLUSIONS: Greater consideration of maturation is needed within training systems and further research is warranted to understand these experiences in more depth and their implications for the physical and psychological wellbeing of young people in dance.

An Exploration of Machine-Learning Estimation of Ground Reaction Force from Wearable Sensor Data.

This study aimed to develop a wearable sensor system, using machine-learning models, capable of accurately estimating peak ground reaction force (GRF) during ballet jumps in the field. Female dancers (n = 30) performed a series of bilateral and unilateral ballet jumps. Dancers wore six ActiGraph Link wearable sensors (100 Hz). Data were collected simultaneously from two AMTI force platforms and synchronised with the ActiGraph data. Due to sensor hardware malfunctions and synchronisation issues, a multistage approach to model development, using a reduced data set, was taken. Using data from the 14 dancers with complete multi-sensor synchronised data, the best single sensor was determined. Subsequently, the best single sensor model was refined and validated using all available data for that sensor (23 dancers). Root mean square error (RMSE) in body weight (BW) and correlation coefficients (r) were used to assess the GRF profile, and Bland-Altman plots were used to assess model peak GRF accuracy. The model based on sacrum data was the most accurate single sensor model (unilateral landings: RMSE = 0.24 BW, r = 0.95; bilateral landings: RMSE = 0.21 BW, r = 0.98) with the refined model still showing good accuracy (unilateral: RMSE = 0.42 BW, r = 0.80; bilateral: RMSE = 0.39 BW, r = 0.92). Machine-learning models applied to wearable sensor data can provide a field-based system for GRF estimation during ballet jumps.

Study of top ballet school students revealed large deficiencies in their body weight and body fat.

AIM: This study assessed the nutritional status and physical activity levels of 150 female students aged 10-18 from three top Polish ballet schools, where the most promising dancers go on to pursue professional ballet careers. METHODS: We analysed the girls' body composition, physical activity level (PAL) and PAL coefficient. The ballet students also completed a questionnaire. RESULTS: The results revealed large deficiencies in the body weight and body fat of the young ballerinas. The mean body mass index (BMI) for the group was 16.8 kg/m2 . Polish centile charts showed that 18% of the girls had BMIs below the norm and 54% had a lower than average body fat content, with a mean of 15.6%. The body fat content was lowest (13.8%) in the 13- to 15-year age group. On average, girls aged 10-12 had 15.7% body fat, while girls aged 16-18 had 18.4%. The mean values for the anthropometric measurements were higher in older girls. The majority (72%) of the respondents reported high physical activity levels, defined as more than 15 hours of exercise per week. CONCLUSION: Special attention should be paid to low BMIs and body fat in young ballet school dancers aged 10-15 years.

Musculoskeletal injuries in professional modern dancers: a prospective cohort study of 15 years.

We analysed work-related musculoskeletal injuries (WMSI) in two modern dance companies to determine whether injury rates decreased and patterns altered compared to previous 3-yr and 6-yr audits (0.48 and 0.25/1000-hrs exposure respectively). In this prospectively designed 15-yr cohort study, data were collected in 30-dancer Company-1 and 12-dancer Company-2. In-house physical therapists tracked WMSI and time-loss-injuries for 159 dancers (42 dancers/yr). 15-yrs were grouped into five 3-yr blocks for comparison with prior audits. Negative binomial logistic regression analyses were conducted with exposure-hrs converted to the natural log and used as the offset variable. Block and company were categorical predictors for dependent variables: WMSI, time-loss-injuries, trauma-injuries and overuse-injuries (p < 0.05). 69% of dancers reported WMSI; 45% sustained at least one time-loss-injury. Company-1, with greater annual exposure, was 1.6-times more likely to sustain time-loss-injuries (p = 0.016, CI = 1.095-2.422) and 5.6-times more likely to sustain time-loss overuse-injuries (p = 0.003, CI = 1.812-17.327). Compared to Block-1, WMSI and time-loss-injuries decreased in Blocks-2, 3, and 5 (p ≤ 0.027). The ratio of time-loss overuse to trauma-injuries was reversed, with trauma-injuries accounting for over 80% of injuries by Block 5. Time-loss-injuries averaged 0.16 injuries/1000-hrs, lower than rates in ballet and sports. Decreased injury rates and changed injury patterns demonstrate efficacious injury management and prevention programming.