Relative energy deficiency in dance (RED-D): a consensus method approach to REDs in dance.

Relative energy deficiency in sport (REDs) is a potentially severe, challenging, broad-spectrum syndrome with potential negative health and performance outcomes. The numerous research publications and International Olympic Committee consensus statements relating to REDs testify to the challenges faced in early identification or screening, diagnosis and management. Like sport, dance, in its simplest form, can be identified as an activity resulting in physiological energy demands and, as such, requires appropriate energy availability concerning energy expenditures. However, the specificity of physiological and psychological demands in dance must be considered when considering REDs. An environment where physical activity can exceed 30 hours per week and where culture may instil a value that thinness is required puts dancers at increased risk for REDs. The purpose of this study was to provide dance-specific guidance dance on this complex condition. An RAND/UCLA Delphi Panel method with nominal group technique was used to review the literature from REDs to evaluate how it may relate to dance. In addition to the EP, which was assembled from a multidisciplinary background with expertise in REDs and multiple genres of dance, six focus groups were commissioned. Four of the focus groups were drawn from the EP members and two additional focus groups formed by dancers and artistic leaders. These panels were used to guide the development of a RED-D diagnosis pathway, management plan and risk stratification and return to dance pathway. The dance-specific pathways are designed to be a practical tool for guiding and supporting clinicians managing RED-D. Furthermore, this paper represents an important focus of this area in dance and serves to stimulate discussion and further research within the sector.

Reliability, Variability and Minimal Detectable Change of the Isometric Mid-Thigh Pull in Adolescent Dancers.

INTRODUCTION: The importance and potential benefits of muscular strength in the adolescent's development for health and fitness has been demonstrated in the literature. Maximal muscular strength and its assessment, however, is not a primary assessment criterium in the selection of young talented dancers. METHODS: The present study evaluated the within- and between session reliability, variability, and minimal detectable change (MDC) of the isometric mid-thigh pull (IMTP). Thirty-five participants (female n = 17) participated in 2 identical assessments on the same day with 4-hour break in between. Three 3-second IMTP were performed, and the mean peak force value was used for the analyses. RESULTS: Within-session the ICC indicated excellent reliability (ICC = .99, 95% CI: 0.98-0.99). Between-session reliability was excellent (ICC = .98, 95% CI: 0.95-0.99). The standard error of measurement was 4% (48 N), the minimum detectable change was 12% (134 N) and the CV was 3%. There were no within-session statistically significant differences, but statistically significant differences between-session were observed (P < .001). Limits of agreement ranged from -121 N (95% CI -186 to -56 N) to 307 N (95% CI 243-372 N). CONCLUSION: The observed results demonstrated excellent within- and between sessions reliability, low variability, and an MDC of 12%. The consistency of the within-session scores suggest that peak force data may be obtained with single try efforts. The statistically significant difference in the means of the retest session, however, suggests that the time of the day or the time since entrained awakening may be affecting performance in adolescent dancers. The results of the current study indicate that the IMTP is a reliable assessment tool for maximal muscular strength in adolescent dancers.

Epidemiological Characteristics of Foot and Ankle Injuries in 2 Professional Ballet Companies: A 3-Season Cohort Study of 588 Medical Attention Injuries and 255 Time-Loss Injuries.

Background: The foot and ankle are often reported as the most common sites of injury in professional ballet dancers; however, epidemiological research focusing on foot and ankle injuries in isolation and investigating specific diagnoses is limited. Purpose: To investigate the incidence rate, severity, burden, and mechanisms of foot and ankle injuries that (1) required visiting a medical team (medical attention foot and ankle injuries; MA-FAIs) and (2) prevented a dancer from fully participating in all dance-related activities for at least 24 hours after the injury (time-loss foot and ankle injuries; TL-FAIs) in 2 professional ballet companies. Study Design: Descriptive epidemiological study. Methods: Foot and ankle injury data across 3 seasons (2016-2017 to 2018-2019) were extracted from the medical databases of 2 professional ballet companies. Injury-incidence rate (per dancer-season), severity, and burden were calculated and reported with reference to the mechanism of injury. Results: A total of 588 MA-FAIs and 255 TL-FAIs were observed across 455 dancer-seasons. The incidence rates of MA-FAIs and TL-FAIs were significantly higher in women (1.20 MA-FAIs and 0.55 TL-FAIs per dancer-season) than in men (0.83 MA-FAIs and 0.35 TL-FAIs per dancer-season) (MA-FAIs, P = .002; TL-FAIs, P = .008). The highest incidence rates for any specific injury pathology were ankle impingement syndrome and synovitis for MA-FAIs (women 0.27 and men 0.25 MA-FAIs per dancer-season) and ankle sprain for TL-FAIs (women 0.15 and men 0.08 TL-FAIs per dancer-season). Pointe work and jumping actions in women and jumping actions in men were the most common mechanisms of injury. The primary mechanism of injury of ankle sprains was jumping activities, but the primary mechanisms of ankle synovitis and impingement in women were related to dancing en pointe. Conclusion: The results of this study highlight the importance of further investigation of injury prevention strategies targeting pointe work and jumping actions in ballet dancers. Further research for injury prevention and rehabilitation strategies targeting posterior ankle impingement syndromes and ankle sprains are warranted.

The Relationship of Year Group and Sex on Injury Incidence and Countermovement Jump in Adolescent Ballet Dancers: A Cross-Sectional Analysis.

INTRODUCTION: Pre-professional ballet training involves long training hours from an early age that could influence young dancers' physical performance and injury incidence. This cross-sectional analysis investigated the relationship of year group and sex with countermovement jump and injury incidence (primary outcome) in adolescent ballet dancers at a pre-professional dance school.
Method: Countermovement jump (CMJ) height was recorded at the start of the academic year for 179 participants (M = 68, F = 111) spread across eight year-groups. Injury etiology and incidence was prospectively recorded over a 6-month period (September through February) by the medical team using a time-loss definition.
Results: Between-subject statistically significant differences were reported for sex [F(1, 153) = 101.46; p < 0.001], year group [F(7, 153) = 12.57; p < 0.001], and sex*year group [F(7, 153) = 9.22; p < 0.001]. Mean CMJ across the year groups ranged between 24.7 to 41.3 cm for males and 23.5 to 25.1 cm for females. Injury incidence per dancer was 0.84 (CI: 0.13, 1.56) and injury incidence per 1,000 hours of dance was 1.94 (CI: 1.63, 2.25). No statistically significant differences between sexes or year groups were reported for injury incidence per 1,000 dance hours and time-loss. Hours dancing was statistically significantly positively associated with CMJ (r = .481, p < 0.05) and negatively associated with injury incidence (r = -.253, p < 0.05) for males; for females it was positively associated with time-loss (r = .254, p < 0.05).
Conclusion: Even though CMJ was cross-sectionally monitored, the expected increased physical abilities in males as they grew older and progressed through their training was observed. Females did not indicate a similar increase in their physical ability, but they seemed to become more susceptible to injuries as they grow older. The lack of this speculative physiological development for the females may be associated with the ballet-only approach in their training. The use of CMJ as an injury screening tool may be limited, however, it could still be used as a tool to monitor physiological and fundamental motor skill development of adolescent dancers, as jumping is an integral part of ballet.

Neuromuscular Training in Pre-Professional Ballet Dancers: A Feasibility Randomized Controlled Trial.

INTRODUCTION: It is well documented that there is high prevalence of injuries in pre-professional and professional ballet dancers. Current evidence from high in quality and quantity research on in- jury prevention in sport indicates that interventions can reduce injury risks by 30% to 50%. Injury prevention research in dance is limited. The aim of this study was to assess the feasibility (adherence, fidelity, and practicality) of a randomized controlled trial for the utilization of neuromuscular training in pre-professional ballet dancers.
Methods: A convenience sample of 22 pre-professional ballet dancers were randomized into an intervention and control group. The intervention group took part in a neuromuscular-based training workout, five times per week before the ballet class, for 10 weeks. The intervention was an adaptation of the FIFA 11+, an injury prevention intervention and is called 11+ Dance. The intervention consisted of low intensity bodyweight exercises that lasted 20 to 30 minutes performed daily.
Results: Intervention adherence was 38% ± 8%, with higher participation at the beginning of the study. Attendance for post-testing was low 45% and 36% for the intervention and control group, respectively, mainly due to injury. There were no adverse effects reported, however, the participants reported delayed onset muscle soreness at the beginning of the intervention, indicating that there may be a potential training effect. Fear of muscle hypertrophy and fatigue were also reported as reasons for attrition. The repeated measures ANOVA revealed statistically non-significant differences for the countermovement jump F(1, 9) = 0.36, p = 0.564, η² p= 0.04; reactive strength index F(1, 7) = 0.02, p = 0.885, η² p= 0.003; and the isometric mid-thigh pull F(1, 12) = 0.002, p = 0.967, η² p= 0.000.
Conclusion: The results of the study, together with the feedback from the participants, suggest that some protocol modifications are necessary for the feasibility of a randomized controlled trial in a pre-professional setting. The current trial has produced valuable information for the intervention frequency and load prescription.

Dancers' heart: Cardiac screening in elite dancers.

Using electrocardiography and echocardiography, we screened elite men and women ballet dancers for abnormal cardiovascular conditions using an observation design with blinded clinical analysis of cardiac function tests. Fifty-eight (females n = 33) elite professional ballet dancers (age: 26.0 ± 5.7 years, body mass index: 19.9 ± 2.2 kg/m2) with no past or present history of cardiovascular disease volunteered. Participants were assessed via a 12-lead electrocardiography and two-dimensional echocardiography for cardiac function. Electrocardiography revealed that 83% of the dancers demonstrated normal axis, while 31% had incomplete right bundle branch block and 17% had sinus bradycardia; none showed any abnormal findings. Findings from the echocardiography were also normal for all participants and comparable to their counterparts in other sports. Significant differences (p < 0.05) were detected in almost all studied echocardiographic parameters between males and females. In conclusion, heart function and structure seem to be normal in elite ballet dancers, placing them at low risk for sudden cardiac death and performance-related cardiovascular complications. Larger samples are required to confirm these findings.

Organisational resilience at the University of Northampton: Developing immunity to a full spectrum of threats.

This paper introduces the concepts of immunity and full-spectrum threats in the context of business continuity and resilience planning at a UK higher education institution. It also describes the approach taken by the University of Northampton to build a reliable response capability through behavioural change at strategic and operational levels. It is hoped that the experience and processes presented will enable readers to complement their thinking, planning and exercising.

Longitudinal Bi-directional Effects of Disordered Eating, Depression and Anxiety.

OBJECTIVE: The present study aims to explore the potentially longitudinal bi-directional effects of disordered eating (DE) symptoms with depression and anxiety. METHOD: Participants were 189 (49.5% male) adolescents from Melbourne, Australia. DE, depressive and anxiety symptoms were assessed at approximately 15, 16.5 and 18.5 years of age. RESULTS: Analysis of longitudinal bi-directional effects assessed via cross-lagged models indicated that DE symptoms of eating and shape/weight concerns were risk factors for anxiety. Results also showed that depression was a risk factor for eating concerns. CONCLUSION: Our findings provide preliminary evidence that preventative measures designed to target concerns about eating and shape/weight might be most efficacious in reducing the transmission of effects between symptoms of DE, depression and anxiety. Copyright © 2017 John Wiley & Sons, Ltd and Eating Disorders Association.

Assessment of Maximum Aerobic Capacity and Anaerobic Threshold of Elite Ballet Dancers.

An athlete's cardiorespiratory profile, maximal aerobic capacity, and anaerobic threshold is affected by training regimen and competition demands. The present study aimed to ascertain whether there are company rank differences in maximal aerobic capacity and anaerobic threshold in elite classical ballet dancers. Seventy-four volunteers (M 34, F 40) were recruited from two full-time professional classical ballet companies. All participants completed a continuous incremental treadmill protocol with a 1-km/hr speed increase at the end of each 1-min stage until termination criteria had been achieved (e.g., voluntary cessation, respiratory exchange ratio <1.15, HR ±5 bpm of estimated HRmax). Peak VO2 (5-breathe smooth) was recorded and anaerobic threshold calculated using ventilatory curve and ventilatory equivalents methods. Statistical analysis reported between-subject effects for gender (F1,67=35.18, p<0.001) and rank (F1,67=8.67, p<0.001); post hoc tests reported soloists (39.5±5.15 mL/kg/min) as having significantly lower VO2 peak than artists (45.9±5.75 mL/kg/min, p<0.001) and principal dancers (48.07±3.24 mL/kg/min, p<0.001). Significant differences in anaerobic threshold were reported for age (F1,67=7.68, p=0.008) and rank (F1,67=3.56, p=0.034); post hoc tests reported artists (75.8±5.45%) having significantly lower anaerobic threshold than soloists (80.9±5.71, p<0.01) and principals (84.1±4.84%, p<0.001). The observed differences in VO2 peak and anaerobic threshold between the ranks in ballet companies are probably due to the different rehearsal and performance demands.

Dancer perceptions of the force reduction of dance floors used by a professional touring ballet company.

The mechanical properties of dance floors have the potential to influence dancers' performance and injury risk. Little information is available that describes dancers' preferences for dance floor mechanical properties. Investigation of dancers' perceptions of varied dance floors can serve to enlighten governing bodies, floor manufacturers, and the dance community. The aim of this study was to assess the perceptions of dancers from a touring professional ballet company regarding four floors with varied force reduction (FR) that were created to replicate those used by the company in normal dance training and performance. A specialized questionnaire was developed that incorporated a series of qualitative and quantitative measures that could be used by participants to express their perceptions of the custom built dance floors. Floor FR was quantified with reference to the protocols specified by European standards. Dancer perceptions were in general agreement with floor FR values; however, some discrepancies were observed. Dancers expressed a preference for floor FR within the mid to upper limits (57% to 72%) of the European standards, although a minority preferred low FR (approximately 36%) floors. A limited ability to perceive inconsistencies in FR across test floors was observed, which may have implications for injury risk. Investigation of the perceptions of dancers from more diverse backgrounds, on floors that provide a closer representation of typical dance studio and stage sizes, over longer periods of time, would provide further insight into the perceptual and adaptive responses of dancers to varied floor mechanical properties.

Dance floor mechanical properties and dancer injuries in a touring professional ballet company.

OBJECTIVES: The mechanical properties of the floors used by dancers have often been suggested to be associated with injury, yet limited etiological evidence is available to support this hypothesis. The dance floors at three theatres regularly used by a touring professional ballet company were mechanically quantified with the aim of comparing floor properties with injury incidence in dancers. DESIGN: Cross sectional. METHODS: Test points on the floors were quantified in accordance with European Sports Surface Standard protocols for force reduction. Injuries and associated variables occurring within the ballet company dancers during activity on the three floors were recorded by the company's medical staff. An injury was recorded if a dancer experienced an incident that restricted the dancer from performing all normal training or performance activities for a 24 h period. Injuries were delimited to those occurring in the lower limbs or lumbar region during non-lifting tasks. RESULTS: Floor construction varied between venues and a range of floor mechanical properties were observed. None of the floors complied with the range of force reduction values required by the European Sport Surface Standards. The highest injury rate was observed on the floor with the greatest variability of force reduction magnitudes. No difference in injury frequency was observed between the venues with the highest and lowest mean force reduction magnitudes. CONCLUSIONS: Professional dancers can be required to perform on floors that may be inadequate for safe dance practice. Intra-floor force reduction variability may have a stronger association with injury risk than mean floor force reduction magnitude.

The influence of winter vitamin D supplementation on muscle function and injury occurrence in elite ballet dancers: a controlled study.

OBJECTIVES: Athletes who train indoors during the winter months exhibit low serum 25-hydroxyvitamin D [25(OH)D] concentrations due to a lack of sunlight exposure. This has been linked to impaired exercise performance. The purpose of this study was to assess the effects of oral vitamin D3 supplementation on selected physical fitness and injury parameters in elite ballet dancers. DESIGN: Controlled prospective study. METHODS: 24 elite classical ballet dancers (intervention n=17; control n=7) participated in a controlled 4-month oral supplementation of vitamin D3 (2000 IU per day). Isometric muscular strength and vertical jump height were measured pre and post intervention. Injury occurrence during the intervention period was also recorded by the in-house medical team. Repeated measures ANOVA and Mann-Whitney-U statistical tests were used and significance was set at p ≤ 0.05. RESULTS: Significant increases were noted for the intervention group for isometric strength (18.7%, p<0.01) and vertical jump (7.1%, p<0.01). The intervention group also sustained significantly less injuries than the controls during the study period (p<0.01). CONCLUSIONS: Oral supplementation of vitamin D3 during the winter months has beneficial effects on muscular performance and injury occurrence in elite ballet dancers.

The effect of a comprehensive injury audit program on injury incidence in ballet: a 3-year prospective study.

OBJECTIVE: The aim of this study was to determine whether an intervention with individualized conditioning program based on injury history and functional movement screening would be effective in reducing ballet injury incidence. DESIGN: Prospective 3-year epidemiological study. SETTING: Professional ballet company and its in-house medical facility. PARTICIPANTS: Dancers from a professional ballet company over the 3-year study period. Participant numbers ranged from 52 to 58 (year 1: 52; year 2: 58; year 3: 53). INTERVENTIONS: The intervention consisted of individual conditioning programs developed using injury history and functional movement screening. Analysis was undertaken of the all dancers who were present in the company during the study period. The significance of change in injuries over a 3-year period was determined using a Poisson distribution model. MAIN OUTCOMES MEASURES: To determine whether individual conditioning programs resulted in a decrease in injury incidence over the study period. RESULTS: The injury count reduced significantly in years 2 and 3 (P < 0.001). Injury incidence for male dancers declined from year 1 (in year/1000 h) (4.76/1000 h) to year 2 (2.40/1000 h) and year 3 (2.22/1000 h). For women, a reduction in the injury incidence was observed from year 1 (4.14/1000 h) to year 2 (1.71/1000 h) and year 3 (1.81/1000 h). CONCLUSIONS: Through prospective injury surveillance, we were able to demonstrate the benefit of individualized conditioning programs based on injury history and functional movement screening in reducing injuries in ballet. CLINICAL RELEVANCE: The implementation of well-structured injury surveillance programs can impact on injury incidence through its influence on intervention programs.

Vitamin D status in professional ballet dancers: winter vs. summer.

OBJECTIVE: Serum 25-hydroxyvitamin D is produced by the exposure of the skin to sunlight. Therefore athletes who train indoors, such as dancers, are vulnerable to vitamin D deficiency. The purpose of the study was to evaluate the serum 25-hydroxyvitamin D status in UK professional dancers during periods of reduced and increased sunlight exposure (i.e., winter vs. summer), and to assess the impact on bone metabolism and risk of injury. DESIGN: Cohort study. METHODS: 19 elite classical ballet dancers (age 26±8.86yr; height 1.66±8.84m; mass 54.3±10.47kg) were monitored over a 6 month period for 25-hydroxyvitamin D, PTH and blood serum bone turnover markers (CTX and PINP) along with injury data. Repeated measure ANOVA and Wilcoxon and Chi-square analyses were used and significance was set at p≤0.05. RESULTS: Significant changes were noted between the winter and summer test dates for 25-hydroxyvitamin D (14.9ng/ml vs. 23.9ng/ml; p<0.001), PTH (38.7pg/ml vs. 26.3pg/ml; p<0.001) and PINP (89.9ng/ml vs. 67.6ng/ml; p<0.01). The oral contraceptive had a significant effect on serum 25-hydroxyvitamin D, PTH and CTX. Soft tissue injuries were significantly lower in summer compared to winter period (winter=24, summer=13; p<0.05). CONCLUSIONS: Professional ballerinas characterized by a high incidence of low serum 25-hydroxyvitamin D levels which improve marginally in the summer. These dancers also demonstrate a higher injury incidence in the winter. Oral contraception seems to increase serum 25-hydroxyvitamin D levels and has a positive effect on bone metabolism.

Ballet injuries: injury incidence and severity over 1 year.

STUDY DESIGN: Prospective, descriptive single-cohort study. OBJECTIVE: To assess the incidence and severity of injuries to a professional ballet company over 1 year. METHODS: Data for an elite-level ballet company of 52 professional dancers were collected by an in-house medical team using a time-loss injury definition. RESULTS: A total of 355 injuries were recorded, with an overall injury incidence of 4.4 injuries per 1000 hours (female, 4.1; male, 4.8; P>.05) and a mean of 6.8 injuries per dancer (female, 6.3; male, 7.3; P>.05). Mean injury severity was 7 days (female, 4; male, 9; P<.05). Most injuries were classified as overuse (64%; female, 68%; male, 60%; P>.05); mean severity of injury was 3 days for females and 9 days for males (P<.05). The percentage of traumatic injuries was 32% for females and 40% for males (P<.05); the corresponding severity was 6 and 10 days, respectively (P<.05). CONCLUSION: The relatively high number of injuries reported and the resulting loss of dance time support the need to introduce interventions to reduce the risk of injury in professional dancers.J Orthop Sports Phys Ther 2012;42(9):781-790. Epub 19 July 2012. doi:10.2519/jospt.2012.3893.

Comparative analysis of the retinal potential of embryonic stem cells and amniotic fluid-derived stem cells.

Photoreceptors have recently been generated from mouse and human embryonic stem cells (ESCs), although ethics concerns impede their utilization for cell replacement therapy for retinal disease. Extra-embryonic tissues have received attention as alternative therapeutic sources of stem cells. Human and mouse amniotic fluid-derived stem cells (AFCs) have been reported to be multipotent and express embryonic and adult stem cell markers. Here, in vitro conditions that generate retinal cells from ESCs were used to analyze and compare the retinal potential of murine AFCs and ESCs. We show that AFCs express pluripotency markers (Nanog, Sox2, and Oct3/4) as well as retinal transcription factor genes (Et, Lhx2, Tll1, Six6, Otx2, Pax6, and Fgf15). AFCs from amniotic fluid of Fgf15.gfp, Nrl.gfp, and Crx.gfp embryos cultured in retinal proliferation and differentiation conditions failed to switch on these retinal transgenes. AFCs cultured in retinal-promoting conditions, effective on ESCs, showed reduced expression of retinal markers. Retinal co-cultures activated retinal genes in ESCs but not in AFCs, and migration assays in retinal explants showed limited migration of AFCs compared with ESCs. Unlike ESCs, AFCs do not express the early embryonic ectodermal gene Utf1 and Western analysis of AFCs identified only the B isoform of Oct3/4, rather than the isoform A present in ESCs. We conclude that AFCs have restricted potential and differ considerably from ESCs and retinal progenitor cells. Reprogramming to induce pluripotency or new differentiation protocols will be required to confer retinal potential to AFCs as expression of a subset of pluripotency and retinal markers is not sufficient.

The cardiorespiratory, anthropometric, and performance characteristics of an international/national touring ballet company.

This study examined the cardiorespiratory and anthropometric indices of professional classical ballet dancers in relation to company seniority, gender, and supplemental training. Forty-nine participants from an international touring company carried out a peak Vo(2) test and vertical jump test. Anthropometric measurements and supplemental training activities were also recorded for each participant. Statistical analyses showed significant differences between gender and dancer seniority levels. Gender differences were seen for jump height (M = 52.7 +/- 7.12 cm; F = 37.6 +/- 5.32 cm) and peak Vo(2) (M = 49.32 +/- 3.72 ml.kg(-1).min(-1); F = 43.3 +/- 5.16 ml.kg(-1).min(-1)). Differences were also seen between dancer levels for peak Vo(2) (artist = 46.47 +/- 4.67 ml.kg(-1).min(-1); first artist = 42.72 +/- 5.81 ml.kg(-1).min(-1); soloist = 43.38 +/- 7.14 ml.kg(-1).min(-1); principal = 49.04 +/- 3.63 ml.kg(-1).min(-1)) and jump height (artist = 42.0 +/- 9.11 cm; first artist = 50.33 +/- 11.65 cm; soloist = 45.6 +/- 9.78 cm; principal = 44.67 +/- 9.53 cm). Pairwise post hoc comparisons showed that corps and principals had significantly greater relative peak Vo(2) than first artists and soloists (p < 0.05), while soloists and first artists had significantly greater jump heights compared to principals and corps (p < 0.05). Analysis of covariance modeling indicated that the self-reported mode of supplemental training had no association with relative peak Vo(2) or the percentage at which ventilatory threshold occurred. The present study has provided further insight into the cardiorespiratory profiles of classical ballet dancers, where soloists have significantly greater power capacities compared to principals and corps, who in turn had significantly greater aerobic power. These data can help guide strength and conditioning intervention strategies that need to take into account the nuances of the different seniority levels within a dance company.