Lower leg and foot contributions to turnout in female pre-professional dancers: A 3D kinematic analysis

Sensing Technology for Assessing Motor Behavior in Ballet: A Systematic Review

Background

Human performance in classical ballet is a research field of growing interest in the past decades. Technology used to acquire data in human movement sciences has evolved, and is specifically being applied to evaluate ballet movements to better understand dancers’ profiles. We aimed to systematically review sensing technologies that were used to extract data from dancers, in order to improve knowledge regarding the performance of ballet movements through quantification.

Methods

PubMed, MEDLINE, EMBASE, and Web of Science databases were accessed through 2020. All studies that used motor control tools to evaluate classical ballet movements, and possible comparisons to other types of dance and sports movements were selected. Pertinent data were filled into a customized table, and risk of bias was carefully analyzed.

Results

Eighty studies were included. The majority were regarding classical ballet and with pre-professional dancers. Forty-four studies (55%) used two or more types of technology to collect data, showing that motion capture technique, force plates, electromyography, and inertial sensors are the most frequent ways to evaluate ballet movements.

Discussion

Research to evaluate ballet movements varies greatly considering study design and specific intervention characteristics. Combining two or more types of technology may increase data reliability and optimize the characterization of ballet movements. A lack of studies addressing muscle–brain interaction in dancers were observed, and given the potential of novel insights, further studies in this field are warranted. Finally, using quantitative tools opens the perspective of defining what is considered an elite dancer.

Comparison of hallux valgus deformed ballerinas and sedentary individuals in terms of balance parameters

BACKGROUND

We aimed to compare static and dynamic balance parameters and health quality parameters in ballerina and non-ballerina adolescents with hallux valgus deformity.

METHODS

Forty five volunteer female adolescent ballet students between the ages of 7 and 17, with hallux valgus were recruited. Group 1 = in the control group, 31 sedentary adolescents with hallux valgus were included. Group 2 = Romberg test and Flamingo test were used for static balance. The SEBT (Star Excursion Balance Test) was used to measure dynamic balance.

RESULTS

Age, sex, and body mass index (BMI) characteristics were similar between ballerina and control groups (P < .05). The Romberg test stands upright with closed eyes, with a significant difference 47.22 in group 1 and 38.13 in group 2. In contrast there was a significant difference between the two groups in the Romberg test single limb with eyes open and closed. For open eyes single limb test mean score was 55.06 in ballerinas and 44.2 in sedentary group, similarly single limb test with closed eyes mean score was 25.68 in group 1 and 18.67 in group 2.

CONCLUSION

In conclusion, the results of this study show that ballerinas have better single-limb and closed-eye balance than sedentary individuals with HV deformities.

The Impact of Hallux Valgus on Adolescent Ballet Dancer Balance and Health-Related Quality of Life Scores

BACKGROUND

It is well-known that hallux valgus (HV) alters foot biomechanics. In different populations, HV and postural stability has been studied, but HV and the adolescent ballet dancer has not been studied. The aims of this study were to explore the effect of HV on adolescent ballet dancers' balance and to assess the health-related quality of life (HRQOL) of adolescent ballet dancers with HV.

METHODS

Female ballet dancers aged 8 to 16 years were screened prospectively and divided into two groups: those with HV (group 1) and those without HV (group 2). The HV diagnosis was made clinically. The groups were compared according to balance parameters and HRQOL questionnaires.

RESULTS

In group 1 (n = 31) and group 2 (n = 24), the mean age was 11.6 years and 12.2 years, respectively. Mean first metatarsophalangeal angle was 13.4° (range, 10°-15°) in group 2 and 19.8° (range, 16°-25°) in group 1. A statistically significant difference was found according to the nonparametric Mann-Whitney U test results in the comparison of HV angle between groups. According to Spearman rho correlation analysis, it was determined that the increase in HV angle caused deterioration in the flamingo static balance test (r = 0.552; P = .019). No significant relationship was found between HRQOL questionnaires and the presence of HV (P > .05).

CONCLUSIONS

Adolescent ballet dancers experience static balance impairment due to HV angle increase. Clinical measurement of HV and application of balance parameters made easy without need of set ups to perform evaluation with high numbers of participants in concordance with the literature.

External rotation of the foot position during plantarflexion increases non-uniform motions of the Achilles tendon

The medial (GM) and lateral gastrocnemius (GL) muscles enroll to different subparts of the Achilles tendon to form their respective subtendons. The relative gastrocnemii activations during submaximal plantarflexion contraction depend on the position of the foot in the horizontal plane: with toes-in, GL activation increases and GM activation decreases, compared to toes-out. The aim of the current study was to investigate whether horizontal foot position during submaximal isometric plantarflexion contraction differently affects the subtendons within the Achilles tendon in terms of their (i) length at rest, and (ii) elongations and distal motions. Twenty healthy subjects (12 females/8 males) participated in the study. Three-dimensional ultrasound images were taken to capture subtendon lengths at rest and during isometric contraction. Ultrasound images were recorded at the distal end of Achilles tendon (sagittal plane) during ramped contractions and analyzed using a speckle tracking algorithm. All tasks were conducted twice, ones with toes-in and ones with toes-out. At rest, subtendons were shorter with toes-out compared to toes-in. During contraction, the GM subtendon lengthened more in toes-out, compared to the GL, and vice versa (all p <.01). The relative motions within the Achilles tendon (middle minus top layers displacements) were smaller in toes-in compared to toes-out (p =.05) for higher contraction intensity. Our results demonstrated that the horizontal foot position during plantarflexion contraction impacts Achilles tendon motions. Such findings may be relevant in a clinical context, for example in pathologies affecting Achilles tendon motions such as Achilles tendinopathy.

Identification Model of Writhing Posture of Classical Dance Based on Motion Capture Technology and Few-Shot Learning

Chinese classical dance is cut into the inner verve from a grasp of external form in dance instruction, and the aesthetic fashion and artistic norms of classical dance are established with historical depth. The "professional specificity" of characters and the "language description" of plots are eliminated in Chinese classical dance creation, highlighting the contemporary spirit of classical dance creation. Chinese classical dance was born during the early years of the People's Republic of China. The term "classical dance" did not refer to all Chinese classical dances at the time; rather, it referred to a dance form that embodied China's national spirit and had a classical cultural heritage based on Chinese traditional dance. The average frequency of step-over was 0.9, which was higher than the average rate of basic turnover of 0.75 and step-by-step turnover of 0.5, according to the results of the SPSS19.0 analysis. As a result, except for a few points with loud noise, it can be concluded that stepping over is an effective feature. The recognition model of the somersault posture of classical dance is studied in this paper, a database for real-time acquisition of three-dimensional data of human motion is established, and the Google model of human body characteristics is obtained based on feature plane matching of human body posture, all using motion capture technology and few-shot learning. The above data has good reference and application value for improving teachers' teaching level and arousing students' learning enthusiasm in the dance teaching process when applied to posture teaching and analysis. The captured data can convert human motion in real three-dimensional space into data in virtual three-dimensional space. Motion capture technology converts human motion information into a technology that can be recognized by computers.

Effect of low back pain on clinical-functional factors and its associated potential risk of chronicity in adolescent dancers of classical ballet: cross-sectional study

BACKGROUND

Low back pain (LBP) is a common symptom in classical ballet dancers, which can limit their daily activities and dance training routines. The purpose of the study was to verify the association and comparison of clinical-functional outcomes (spine flexibility and foot posture) between different levels of intensity low back pain in adolescents of classical ballet and the potential risk of chronicity using the STarT back tool.

METHODS

Cross-sectional study.

PARTICIPANTS

78 adolescent girls who practice classical ballet were evaluated and divided into groups according to level of low back pain: mild (n = 21), moderate (n = 17), and high (n = 20), and a control group (n = 20).

MAIN OUTCOME MEASURES

Pain, flexibility of the spine (thoracic and lumbosacral), risk of chronicity for low back pain, and foot posture were assessed using the visual analogue scale, clinical tests, STarT back screening tool (SBST) questionnaire, and foot posture index (FPI), respectively.

RESULTS

Dancers with high-intensity low back pain showed a potential risk of chronicity by the SBST. The spine pain intensity was not different considering thoracic and lumbosacral flexibility in the sagittal plane, but was different with greater supine FPI when compared to control dancers. Mild low back pain was associated with greater supine FPI. The SBST score was associated with higher exposure time-frequency and time of dancing.

CONCLUSION

Adolescents of classical ballet with high-intensity low back pain showed a potential risk of chronicity by the SBST. The level of intensity low back pain did not influence the clinical-functional aspects of spine flexibility in the sagittal plane, but the level of intensity moderate pain promoted changes in foot posture (more supinated). The potential risk of chronicity using the SBST was also associated with higher exposure time-frequency and time of dancing, in adolescents of classical ballet.

The time-continuous association between turnout and axial joint moments in the competitive Irish dance 'fly' landing

Turnout is a key technical and aesthetic element in competitive Irish dance involving external rotation of the lower limb and must be sustained during landings. 'Forced' turnout, aided by floor friction rather than active hip rotation, is likely to result in large internal rotation moments at the knee and ankle, which may increase the risk of injury. The aim of the current study was to establish the relationship between the hip and ankle external rotation vector field and maximum internal rotation moments of the ankle and knee. Thirteen (12 female) competitive Irish dancers performed 10 flys (common Irish dance leap) onto a force plate while being recorded by a ten-camera motion capture system. Time-continuous data were analysed over the duration of landing using statistical parametric mapping (SPM). A positive correlation (p < 0.05) was found between the hip-ankle turnout vector field and maximum ankle internal rotation moments throughout most of the landing. Post-hoc analyses showed that hip external rotation contributed the most to the maximum ankle internal rotation moment (p < 0.05). Increasing hip turnout during landing could reduce internal rotation moments, assuming hip turnout brings the thigh and foot axial orientation more in line with each other.

The effects of acute physical fatigue on sauté jump biomechanics in dancers

Dancers spend large amounts of time practicing and performing, where fatigue may occur, resulting in adverse movement patterns. The purpose of this study was to compare sauté landings before and after acute physical fatigue in experienced female dancers. Twenty-one dancers completed 10 sauté jumps before and after a dance-specific fatigue protocol. A 12-camera motion capture system and a force plate were utilized to collect three-dimensional kinematic and kinetic data. After fatigue, dancers demonstrated an increase in mediolateral centre of mass displacement, pelvis excursion, peak knee abduction, peak ankle eversion and external rotation, as well as decreased peak metatarsophalangeal (MTP) joint extension, indicating less desirable movement patterns. Peak vertical ground reaction force was decreased after fatigue due to a softer landing strategy, demonstrated by increased peak hip flexion, knee flexion, and ankle dorsiflexion. There was some indication of shifting demands demonstrated by an increased peak knee extensor moment and decreased peak MTP flexor moment after fatigue. With jump landing kinematics and kinetics affected after only an average of 5 minutes of dancing, dancers may benefit from developing greater endurance and more eccentric strength to allow them to slow down properly while landing and to sustain the aesthetic demands throughout performance.

Correlation between degree of hallux valgus and kinematics in classical ballet: A pilot study

Hallux valgus is a serious medical concern for classical ballet dancers. Although it is well-known that progression of hallux valgus is related to inappropriate movement techniques in classical ballet, the kinematic relationship between the degree of hallux valgus and ballet techniques has not been substantiated. To develop proper training methods that prevent progression of hallux valgus, this study aimed to investigate the relationship between the degree of hallux valgus and movement techniques in classical ballet. Seventeen female classical ballet dancers at the advanced college-level participated in this study. Kinematic analysis of standing and plié in the first position was conducted via video capture technique. The Pearson product-moment correlation analysis was performed to examine the degree of hallux valgus and the following three kinematic variables: (1) the extent to which turnout is forced by other joints in the lower extremity than the hip joint, (2) the direction difference between the knee and toe in the transverse plane, and (3) the pelvis obliquity angle. Among these kinematic variables, we found a significant correlation between the hallux valgus angle and the pelvis obliquity angle during plié (P = .045). The greater the hallux valgus angle, the greater the retroversion of the pelvis, a result which was contrary to our prediction. We present the first evidence that the degree of hallux valgus correlates with kinematics in a very basic technique of classical ballet.

Mechanical Demands at the Ankle Joint During Saut de Chat and Temps levé Jumps in Classically Trained Ballet Dancers

Background

During ballet, injuries to the Achilles tendon are associated with the take-off phase of various jumps.

Research question

The purpose of the study was to assess differences in mechanical demand on the body, specifically at the ankle, in two single-leg jumps commonly trained in ballet: a saut de chat (SDC) and a temps levé (TL).

Methods

Fifteen classically trained female dancers had 16 reflective markers placed on the lower body and each dancer performed each jump three times on a force plate. The marker position data and ground reaction forces (GRF) were captured synchronously at 250 Hz and 1000 Hz, respectively. Peak vertical GRF, mean rate of force development (RFD), peak ankle moment, and peak ankle power were determined and averaged across trials. Paired t-tests were used to determine differences between the SDC and the TL.

Results

When compared to the TL, the SDC displayed significantly higher peak vertical GRF (p = 0.003), RFD (p = 0.002), and peak ankle moment and power (p < 0.001). The effect sizes for these differences were large for all variables (Cohen’s d > 0.80).

Conclusion

The mechanical demand at the ankle joint is significantly greater for the SDC than the TL.

Prevalence and unique patterns of lower limb hypermobility in elite ballet dancers

OBJECTIVES

Determine the prevalence of lower limb hypermobility in elite dancers and secondarily to describe the patterns of mobility.

DESIGN

Cross sectional.

SETTING

Self-report questionnaires and physical assessments were undertaken at a tertiary dance institution and a professional ballet company.

PARTICIPANTS

Fifty-seven pre-professional and 29 professional ballet dancers (21±4years, 64% female, mean 13.7years training) were recruited.

MAIN OUTCOME MEASURES

Lower Limb Assessment Score (LLAS) was used to assess hypermobility. Prevalence was determined by descriptive statistics, between-leg and -group comparisons were analysed using the chi-square statistic and the pattern of mobility by cluster analyses.

RESULTS

The right leg was significantly more hypermobile than the left for the whole cohort (44% vs 40% meeting ≥7/12 for the LLAS; LLAS mean/12(SD): right:5.0(2.4) and 7.6(1.9); left:4.8(2.1) and 6.7(2.0) in pre-professionals and professionals respectively (p = 0.02)). Subtalar pronation (p < 0.001) and hip abduction/external rotation (left:p = 0.01; right:p < 0.001) were significantly more hypermobile bilaterally in professionals. Three hypermobility profiles on the left and four on the right lower limb were identified.

CONCLUSIONS

This paper presents unique lower limb hypermobility profiles identified in elite dancers.

An analysis of the foot in turnout using a dance specific 3D multi-segment foot model

Introduction

Recent three-dimensional (3D) kinematic research has revealed foot abduction is the strongest predictor of standing functional and forced turnout postures. However, it is still unknown how the internal foot joints enable a large degree of foot abduction in turnout. The primary purpose of this study was to use a dance specific multi-segment foot model to determine the lower leg and foot contributions to turnout that female university-level ballets use to accentuate their turnout.

Methods

Eighteen female dance students (mean age, 18.8 ± 1.6 years) volunteered for this study. Retro-reflective markers were attached to the dancers’ dominant foot. Each dancer performed three repetitions of functional turnout, forced turnout and ten consecutive sautés in first position. Repeated measures ANOVA with Bonferroni adjustments for the multiple comparisons were used to determine the kinematic adjustments, hindfoot eversion, midfoot and forefoot abduction, navicular drop (i.e. lowering of the medial longitudinal arch) and first metatarsophalangeal joint abduction between natural double leg up-right posture and the first position conditions.

Results

Hindfoot eversion (4.6°, p < 0.001) and midfoot abduction (2.8°, p < 0.001) significantly increased in functional turnout compared to the natural double leg up-right posture. Thirteen dancers demonstrated increased first metatarsophalangeal joint (MTPJ) abduction in forced turnout, however no statistically significant increase was found. Navicular drop during sautés in first position significantly increased by 11 mm (p < 0.001) compared to the natural double leg up-right posture.

Conclusion

Our findings suggest dancers do pronate, via hindfoot eversion and midfoot abduction in both functional and forced turnout, however, no immediate association was found between forced turnout and first MTPJ abduction. Foot pronation does play a role in achieving turnout. Further prospective research on in situ measures of the lower limb in turnout and injury surveillance is required to improve our understanding of the normal and abnormal dance biomechanics.

Electronic supplementary material

The online version of this article (10.1186/s13047-019-0318-1) contains supplementary material, which is available to authorized users.