Measurement of the extreme ankle range of motion required by female ballet dancers

The Effects of Pointe Shoes on Ballet Dancers' Biomechanics, Muscle Activity, Movement and Symptoms: A Scoping Review

Introduction: Dancing en pointe requires ballet dancers to stand on the tips of their toes while wearing a structured pointe shoe. Understanding the effect of pointe shoes on ballet dancers' biomechanics, function, symptoms and skin health is essential to guide shoe development and ultimately improve dancer performance. Therefore, the purpose of this scoping review was to map the evidence and identify knowledge gaps related to the effect of wearing pointe shoes on professional and recreational ballet dancers. Method: A scoping review was conducted by searching 6 electronic databases and the International Association for Dance Medicine and Science Bibliography. Results: Thirty-five studies were grouped into 5 categories: pointe shoe factors (eg, toe box and shank, pointe shoe status; 9 studies), shoe types (eg, flat shoes vs demi pointe vs pointe; 10 studies), ballet movements (11 studies), symptoms (5 studies), and intrinsic dancer factors (eg, foot type/toe length; 7 studies). Studies were published between 1979 and 2023, with 72% (n = 23) published between 2006 and 2020. Most (86%) of the studies were cross-sectional. Most studies explored biomechanical outcomes and the most common data collection device was force plates (19 studies). Overall, there was an insufficient volume of evidence for specific research aims. Significant gaps in knowledge exist regarding functional and performance-based outcomes, injury outcomes including exploration of factors such as shoe age/usage, and pointe shoe treatment factors. Conclusions: Currently the field of research suffers from threats to ecological validity, with many study methods not reflecting ballet-specific demands or environments. The impact of pointe shoes on ballet dancers is a developing research area, and this scoping review can help guide future research decisions. Studies need to target the knowledge gaps and employ rigorous ecologically valid study designs and ensure that findings inform shoe design and dancer education to minimize injury and maximize comfort and performance.

Injury incidence and severity in Chinese pre-professional dancers: A prospective weekly monitoring survey

OBJECTIVES

To determine dance injury incidence and severity in full-time Chinese pre-professional dancers.

STUDY DESIGN

Prospective weekly online monitoring survey.

METHODS

Respondents were asked to record all dance-injury incidences between September 2020 and July 2021 using a remote weekly self-report injury monitoring tool. An inclusive definition of injury was used in this study to record all injuries, even if they didn't cause a cessation of training. Data were excluded if respondents completed <90 % of the survey period and had over 3 consecutive weeks of missing data.

RESULTS

450 individuals from 11 different schools were included in the analyses. A total of 1157 injuries were reported over a 30-week academic year. Injury prevalence was 64.9 % and injury incidence was 5.51 injuries per 1000 h. Forty-eight percent of the injuries were minor severity and 41 % were of moderate severity, and the main injury sites were knees (0.89/1000 h), lower back (0.80/1000 h), feet (0.58/1000 h) and groin (0.56/1000 h). Female dancers reported significantly higher injury prevalence and injury incidence, and higher rates of moderate to severe injuries than males. The university group reported higher injury incidence than the adolescent group (p < 0.05), whereas the latter reported higher rates of moderate to severe injuries than the former (p < 0.001).

CONCLUSIONS

The injury incidence found in this study (5.1 injuries/1000 h) is higher than most previous sets of data. Female dancers are at a higher risk of injury and reported higher levels of injury severity than male dancers, especially for the female adolescent group.

Relationships Between Common Preseason Screening Measures and Dance-Related Injuries in Preprofessional Ballet Dancers

OBJECTIVE: To examine modifiable and nonmodifiable factors for associations with dance-related injury among preprofessional ballet dancers over 5 academic years. DESIGN: Prospective cohort study. METHODS: Full-time preprofessional ballet dancers (n = 452; 399 female; median age [range], 15 years [11-21]) participated across 5 academic years at a vocational school. Participants completed baseline screening and online weekly injury questionnaires including dance exposure (hours/week). Zero-inflated Poisson regression models were used to examine associations between potential risk factors measured at baseline and self-reported dance-related injury. RESULTS: In count model coefficients, left one leg standing score (log coefficient estimate, -0.249 [95% CI: -0.478, -0.02]; P = .033) and right unipedal dynamic balance time (log coefficient estimate, -0.0294 [95% CI: -0.048, -0.01]; P>.001) carried a protective effect with increased years of training when adjusted for Athletic Coping Skills Inventory (ACSI) score. A significant association was found for left unipedal dynamic balance time and dance-related injury (log coefficient estimate, 0.013 [95% CI: 0.000, 0.026]; P = .045) when adjusted for years of training and ACSI score. There were no significant associations between dance-related injury and ankle and hip range of motion, active straight leg raise, or Y Balance Test measures. CONCLUSION: When adjusted for years of previous dance training and psychological coping skills, there was a significant association between limb-specific lumbopelvic control and dynamic balance tasks, as well as self-reported dance-related injury in preprofessional ballet. J Orthop Sports Phys Ther 2023;53(11):703-711. Epub 3 October 2023. doi:10.2519/jospt.2023.11835.

Applications of Biomechanical Foot Models to Evaluate Dance Movements Using Three-Dimensional Motion Capture: A Review of the Literature

Dance movement requires excessive, repetitive range of motion (ROM) at the foot-ankle complex, possibly contributing to the high rate of injury among dancers. However, we know little about foot biomechanics during dance movements. Researchers are using three-dimensional (3D) motion capture systems to study the in vivo kinematics of joint segments more frequently in dance-medicine research, warranting a literature review and quality assessment evaluation. The purpose of this literature review was to identify and evaluate studies that used 3D motion capture to analyze in vivo biomechanics of the foot and ankle for a cohort of dancers during dance-specific movement. Three databases (PubMed, Ovid MEDLINE, CINAHL) were accessed along with hand searches of dance-specific journals to identify relevant articles through March 2020. Using specific selection criteria, 25 studies were identified. Fifteen studies used single-segment biomechanical foot models originally created to study gait, four used a novel two-segment model, and six utilized a multi-seg- ment foot model. Nine of the studies referenced common and frequently published gait marker sets and four used a dance-specific biomechanical model with purposefully designed foot segments to analyze the dancers' foot and ankle. Description of the biomechanical models varied, reducing the reproducibility of the models and protocols. Investigators concluded that there is little evidence that the extreme total, segmental, and inter-segmental foot and ankle ROM exerted by dancers are being evaluated during dance-specific movements using 3D motion capture. Findings suggest that 3D motion capture is a robust measurement tool that has the capability to assist researchers in evaluating the in vivo, inter-segmental motion of the foot and ankle to potentially discover many of the remaining significant factors predisposing dancers to injury. The literature review synthesis is presented with recommendations for consideration when evaluating results from studies that utilized a 3D biomechanical foot model to evaluate dance-specific movement.

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.

Avaliação da amplitude do movimento perna-pé. Qual método de aferição é mais fidedigno?

Objetivo Avaliar os métodos de mensuração do movimento perna-pé em tornozelos e pés normais comparando os resultados das medidas clínicas com a mensuração radiográfica e determinar qual é a amplitude do movimento perna-pé considerada normal.

Métodos O movimento perna-pé foi mensurado em 44 pacientes (60 pés) empregando um goniômetro tradicional, goniômetro digital, inclinômetro, aplicativo para smartphone, além da mensuração radiográfica (considerada padrão ouro). A dorsiflexão máxima foi alcançada pedindo ao paciente dar um passo à frente com o pé contralateral e realizar o máximo de dorsiflexão possível no tornozelo estudado sem retirar o calcanhar do solo. Já para a flexão plantar máxima, foi solicitado ao paciente para dar um passo para trás com pé contralateral e fazer o máximo de flexão plantar possível sem retirar o antepé estudado do solo.

Resultados Os valores obtidos na mensuração radiográfica foram maiores do que os obtidos com a mensuração clínica. Quando comparamos apenas os resultados da mensuração clínica, o goniômetro tradicional se mostrou impreciso. Segundo o método radiográfico, a média de amplitude do movimento perna-pé foi de 65,6 graus. Já a média da flexão plantar máxima foi de 34,9 graus, e a média da dorsiflexão máxima foi de 30,7 graus.

Conclusões O método mais adequado para a avaliação da amplitude do movimento perna-pé é o radiográfico. O goniômetro tradicional se mostrou o método clínico mais impreciso. A média de amplitude do movimento perna-pé em adultos jovens e saudáveis foi de 65 graus.

Stretch-Shortening Cycle Performance and Muscle-Tendon Properties in Dancers and Runners

The purpose of this investigation was to elucidate whether ankle joint stretch-shortening cycle performance, isometric and isokinetic plantarflexion strength, and maximal Achilles tendon force and elongation differ between dancers, endurance runners, and untrained controls. To differentiate between dancers, endurance runners, and controls, the authors measured maximal Achilles tendon force and elongation during isometric ramp contractions with ultrasonic imaging, maximal isometric and isokinetic plantarflexion strength with dynamometry, and stretch-shortening cycle function during countermovement hopping and 30-cm drop hopping with a custom-designed sled. The Achilles tendon of dancers elongated significantly (P ≤ .05) more than runners and controls. Dancers were significantly stronger than controls during isometric contractions at different ankle angles. Concentric and eccentric strength during isokinetic contractions at 60°·s-1 and 120°·s-1 was significantly higher in dancers and runners than controls. Dancers hopped significantly higher than runners and controls during hopping tasks. Dancers also possessed significantly greater countermovement hop relative peak power, drop hop relative impulse, and drop hop relative peak power than controls. Finally, dancers reached significantly greater velocities during countermovement hops than runners and controls. Our findings suggest dancing and running require or likely enhance plantarflexion strength. Furthermore, dancing appears to require and enhance ankle joint stretch-shortening cycle performance and tendon elongation.

Association between pre-participation characteristics and risk of injury amongst pre-professional dancers

STUDY DESIGN

Prospective Cohort Study.

BACKGROUND

Few investigations utilize evidence-informed pre-participation evaluation, inclusive injury definitions, and prospective surveillance to identify risk factors for dance-related injuries.

OBJECTIVE

To evaluate pre-participation characteristics that may be associated with greater odds of dance-related musculoskeletal complaints in pre-professional dancers.

METHODS

Full-time pre-professional ballet [n = 85, 77 females, median (range) age 15-years (11-19)] and contemporary [n = 60, 58 females, 19-years (17-30)] dancers underwent pre-participation evaluation: baseline questionnaire, coping skills, body mass index, bone mineral density, ankle range-of-motion, active standing turnout, lumbopelvic control, and balance tests. Self-reported complaints (any physical problem making dance participation difficult, irrespective of medical attention or time-loss) were captured weekly via online questionnaires for one academic year. Self-reported musculoskeletal complaints were recorded weekly (yes/no). Potential risk factors were identified a-priori through systematic review. Associations between potential risk factors and musculoskeletal complaints were examined with generalized linear mixed method regression models.

RESULTS

Response rate was 99%, with 81% of dancers reporting at least one musculoskeletal complaint. Of 1521 complaints (19% first-time, 81% ongoing), the ankle (22%), knee (21%), and foot (12%) accounted for the majority. Injury history [odds ratio (OR) 7.37 (95% CI 3.41, 15.91)] and previous week's dance hours [OR 1.02 (1.01, 1.03)] were associated with dance-related musculoskeletal complaints.

CONCLUSIONS

Prevalence of musculoskeletal complaints amongst pre-professional dancers is high and associated with injury history and training volume. Further understanding of the relationship between training load and injury is needed, with particular consideration of the dynamic and recursive nature of dance injury etiology.

LEVEL OF EVIDENCE

Therapy / Prevention, Aetiology / Harm, level 2b.

Acute Effects of Dry Needling on Myofascial Trigger Points in the Triceps Surae of Ballet Dancers: A Pilot Randomized Controlled Trial

BACKGROUND

There is convincing evidence that dancers suffer injuries to the triceps surae musculature. Research on the immediate effects of dry needling (DN) is limited, and it is important to understand the acute effects of this treatment prior to performance.

PURPOSE

The purpose of this pilot study was to assess the immediate effects of DN on myofascial trigger points in terms of skin surface temperature, pain, active and passive range of motion, and torque production in the triceps surae of ballet dancers.

STUDY DESIGN

Randomized, double-blinded pilot study.

METHODS

Professional ballet dancers that fit inclusion and exclusion criteria (n=11) were randomly assigned to an experimental or control group. The dancers had three pre-determined standard point (SP) measurement spots that were used as a baseline for surface temperature comparisons. The dancers were also palpated for trigger point (TP) spots. Both SP and TP spots were marked for future measurements. The experimental group received DN, while the control group received sham DN (SHAM) to their bilateral calves at the TP spots. Immediately prior to and following treatment, both DN and SHAM groups were tested for skin surface temperature, pain, range of motion, and plantar flexion torque by blinded assessors. Paired t-tests and independent t-tests were performed to examine for differences between groups.

RESULTS

The surface temperature for the TP was higher than the SP measurements prior to intervention (Right calf p= .014; Left calf p= .031). There were no significant changes in VAS scale reported pain and ROM. The plantar flexion torque measurements showed an increase in the DN group of the left calf at the angular velocity of 60 degrees/sec.

CONCLUSION

This was a unique pilot study examining the acute effects of DN on professional ballet dancers. The results were limited due to low sample size. However, the methodology for this study and surface temperature results invites future research.

LEVEL OF EVIDENCE

Level 1b.

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.

Association Between Previous Injury and Risk Factors for Future Injury in Preprofessional Ballet and Contemporary Dancers

OBJECTIVES

To determine the prevalence of self-reported 1-year injury history and examine its association with preparticipation evaluation components aimed at predicting future injury risk (PPE-IP) among preprofessional ballet and contemporary dancers.

DESIGN

Cross-sectional study.

SETTING

Preprofessional ballet school, university contemporary dance program.

PARTICIPANTS

Full-time preprofessional ballet and contemporary dancers.

ASSESSMENT OF RISK FACTORS

Preparticipation evaluation consisted of the Athletic Coping Skills Inventory-28, body mass index, total bone mineral density, ankle range of motion, active standing turnout, lumbopelvic control, unipedal dynamic balance, and Y-Balance test.

MAIN OUTCOME MEASURE

Self-reported 1-year history of dance-related medical attention and/or time-loss injury.

RESULTS

A total of 155 ballet [n = 90, 80 females, median age 15 years (range 11-19)] and contemporary [n = 65, 63 females, median age 20 years (range 17-30)] dancers participated. Forty-six percent (95% confidence interval (CI), 38.4-54.6) reported a 1-year injury history. Self-reported injury history was not associated with any PPE-IP, however, an influence of age and psychological coping skills on the relationship between 1-year injury history and PPE-IP was identified. Multivariable analyses revealed that prevalence of 1-year injury history did not differ by age [referent group <15 years; 15-18 years: odds ratio (OR) 0.80 (95% CI, 0.35-1.79); >18 years: OR 0.69 (95% CI, 0.30-1.56)], or level of psychological coping skills [OR 1.35 (95% CI, 0.61-2.94)].

CONCLUSIONS

The prevalence of self-reported 1-year injury history among preprofessional ballet and contemporary dancers is high. Although measures of PPE-IP did not differ based on injury history, it is important that age and psychological coping skills are considered in future dance injury prevention and prediction research.

LEVEL OF EVIDENCE

Level 3 evidence.

Foot and ankle joint movements of dancers and non-dancers: a comparative study

Ballerinas use their ankle joints more extremely and sustain injuries on the ankle joint more frequently than non-dancers. Therefore, the ankle movement of dancers is important and should be studied to prevent injuries. Measuring ankle joint range of motion (ROM) using radiographs could demonstrate the contribution to motion of each joint. The aim of this study was to analyse and compare ankle joint movements and the ratio of each joint's contribution during movement between dancers and non-dancers, using radiographic images. Dancers have lower dorsiflexion (26.7 ± 6.2°), higher plantarflexion (74.3 ± 7.1°) and higher total (101.1 ± 10.8°) ROMs than non-dancers (33.9 ± 7.0°, 57.2 ± 6.8° and 91.1 ± 9.3°, respectively) (p < 0.05). Although the ROMs were different between the two groups, the ratios of each joint movement were similar between these two groups, in all movements. Regarding total movement, the movement ratio of the talocrural joint was almost 70% and other joints accounted for almost 30% of the movement role in both dancers and non-dancers. Therefore, the differences in ROM between dancers and non-dancers were not a result of a specific joint movement but of all the relevant joints' collaborative movement.

Assessment of female ballet dancers' ankles in the en pointe position using high field strength magnetic resonance imaging

BACKGROUND

The en pointe position of the ankle in ballet is extreme. Previously, magnetic resonance imaging (MRI) of ballet dancers' ankles en pointe was confined to a low field, open MR device.

PURPOSE

To develop a reproducible ankle MRI protocol for ballet dancers en pointe and to assess the positions of the key structures in the dancers ankles.

MATERIAL AND METHODS

Six female ballet dancers participated; each was randomly assigned to stand en pointe while one of her feet and ankles was splinted with wooden rods affixed with straps or to begin with the ankle in neutral position. She lay in an MR scanner with the ankle inside a knee coil for en pointe imaging and inside an ankle/foot coil for neutral position imaging. Proton density weighted images with and without fat suppression and 3D water excitation gradient recalled echo images were obtained en pointe and in neutral position in sagittal, axial, and coronal planes. We compared the bones, cartilage, and soft tissues within and between positions.

RESULTS

No difficulties using the protocol were encountered. En pointe the posterior articular surface of the tibial plafond was incongruent with the talar dome and rested on the posterior talus. The posterior edge of the plafond impinged Kager's fat pad. All participants exhibited one or more small ganglion cysts about the ankle and proximal foot, as well as fluid accumulation in the flexor and fibularis tendon sheaths.

CONCLUSION

Our MRI protocol allows assessment of female ballet dancers' ankles in the extreme plantar flexion position in which the dancers perform. We consistently noted incongruence of the talocrural joint and convergence of the tibia, talus, and calcaneus posteriorly. This protocol may be useful for clinicians who evaluate dancers.

Preventing dance injuries: current perspectives

Dancers are clearly athletes in the degree to which sophisticated physical capacities are required to perform at a high level. The standard complement of athletic attributes - muscular strength and endurance, anaerobic and aerobic energy utilization, speed, agility, coordination, motor control, and psychological readiness - all are essential to dance performance. In dance, as in any athletic activity, injuries are prevalent. This paper presents the research background of dance injuries, characteristics that distinguish dance and dancers from traditional sports and athletes, and research-based perspectives into how dance injuries can be reduced or prevented, including the factors of physical training, nutrition and rest, flooring, dancing en pointe, and specialized health care access for dancers. The review concludes by offering five essential components for those involved with caring for dancers that, when properly applied, will assist them in decreasing the likelihood of dance-related injury and ensuring that dancers receive optimum attention from the health care profession: (1) screening; (2) physical training; (3) nutrition and rest; (4) specialized dance health care; and (5) becoming acquainted with the nature of dance and dancers.

Is goniometry suitable for measuring ankle range of motion in female ballet dancers? An initial comparison with radiographic measurement

Female ballet dancers require extreme ankle motion to attain the demi-plié (weight-bearing full dorsiflexion [DF]) and en pointe (weight-bearing full plantar flexion [PF]) positions of ballet. However, techniques for assessing this amount of motion have not yet received sufficient scientific scrutiny. Therefore, the purpose of this study was to examine possible differences between weight-bearing goniometric and radiographic ankle range of motion measurements in female ballet dancers. Ankle range of motion in 8 experienced female ballet dancers was assessed by goniometry and 2 radiographic measurement methods. The latter were performed on 3 mediolateral x-rays, in demi-plié, neutral, and en pointe positions; one of them used the same landmarks as goniometry. DF values were not significantly different among the methods, but PF values were (P < .05). Not only was PF of the talocrural joint significantly less than the other 2 measurements (P < .001), PF from the goniometric method applied to the x-rays was significantly less than PF obtained from clinical goniometry (P < .05). These data provide insight into the extreme ankle and foot motion, particularly PF, required in female ballet dancers and suggest that goniometry may not be ideal for assessing ankle range of motion in these individuals. Therefore, further research is needed to standardize how DF and PF are measured in ballet dancers.

LEVEL OF EVIDENCE

Diagnostic, Level I.