Does Function Determine the Structure? Changes in Flexor Hallucis Longus Muscle and the Associated Performance Related to Dance Modality: A Cross-Sectional Study.

Background and Objectives: Flexor hallucis longus pathology is one of the most common conditions of the ankle and foot in dancers, due to the high demand of dance movements performed in an extreme plantar flexion and dorsiflexion range of motion. The objectives of this study were to determine the bilateral differences between the thickness and cross-sectional area of the flexor hallucis longus muscle in dancers, to establish possible differences between dance modalities, and to analyze whether there is a correlation between ultrasonographic parameters or performance variables and the dance modality. Material and Methods: A sample of 50 (29 classical and 21 contemporary) full-time pre-professional female dancers were included in the study. The thickness and cross-sectional area of the flexor hallucis longus muscle were evaluated for both limbs using ultrasound imaging. The range of movement of the first metatarsophalangeal joint was measured using functional extension with maximal ankle plantarflexion, balance was measured in a unilateral stance with the heel raised, endurance was evaluated through a modified heel rise fatigue test, and a counter movement jump to assess the vertical jump performance was measured bilaterally. Results: There were no significant differences recorded between the dominant and non-dominant limbs for each variable, within both groups. Contemporary dancers showed a greater thickness and cross-sectional area of the flexor hallucis longus muscle than classical dancers. However, classical dancers showed an increase of balance, endurance, range of movement of the first metatarsophalangeal joint, and counter movement jump with respect to contemporary dancers. Conclusion: Bilateral symmetry was identified in all variables for both groups. The size and performance of the flexor hallucis longus muscle may be influenced by the specific nature of dance modality.

Dance recognition system using lower body movement.

The current means of locating specific movements in film necessitate hours of viewing, making the task of conducting research into movement characteristics and patterns tedious and difficult. This is particularly problematic for the research and analysis of complex movement systems such as sports and dance. While some systems have been developed to manually annotate film, to date no automated way of identifying complex, full body movement exists. With pattern recognition technology and knowledge of joint locations, automatically describing filmed movement using computer software is possible. This study used various forms of lower body kinematic analysis to identify codified dance movements. We created an algorithm that compares an unknown move with a specified start and stop against known dance moves. Our recognition method consists of classification and template correlation using a database of model moves. This system was optimized to include nearly 90 dance and Tai Chi Chuan movements, producing accurate name identification in over 97% of trials. In addition, the program had the capability to provide a kinematic description of either matched or unmatched moves obtained from classification recognition.

Knee injury patterns in young irish dancers.

OBJECTIVE: To characterize knee injury patterns in Irish dancers. METHODS: A retrospective chart review was performed for Irish dancers under age 19 who presented with knee injuries to the sports medicine or orthopedic clinic from January 1, 2000 to December 31, 2010. Data were collected on all knee injuries partially or directly related to Irish dance. Injury was defined as dance-related pain or damage to the structures in the knee that resulted in evaluation in the clinic. Survey data were collected to determine the number of different schools/studios represented by the dancers in the study. RESULTS: Sixty-seven Irish dancers with 86 knee injuries were evaluated. Half (50.7%) of these patients received more than one diagnosis during these visits. Overuse injuries accounted for 90.7% of knee injuries. Time to presentation ranged from less than 1 week to over 1 year. There was a significant difference in time to presentation, with traumatic injuries being evaluated sooner than overuse injuries. The most common diagnoses, accounting for 53.5% of injuries, were patellar tracking disorders, including patellofemoral syndrome, hypermobile patella, and patellar subluxation. CONCLUSION: In Irish dance overuse injuries represent the great majority of knee injuries, and patellofemoral tracking disorders are the most common diagnosis. For many dancers, there is often a delay of weeks to months between the onset of symptoms and evaluation in clinic. Prevention programs could potentially eliminate a large portion of knee pain experienced by young Irish dancers.

Biomechanical research in dance: a literature review.

The authors reviewed the literature, published from 1970 through December 2009, on biomechanical research in dance. To identify articles, the authors used search engines, including PubMed and Web of Science, five previous review articles, the Dance Medicine and Science Bibliography, and reference lists of theses, dissertations, and articles being reviewed. Any dance research articles (English language) involving the use of electromyography, forceplates, motion analysis using photography, cinematography or videography, and/or physics analysis were included. A total of 89 papers, theses/dissertations, and abstracts were identified and reviewed, grouped by the movement concept or specialized movements being studied: alignment (n = 8), plié (8), relevé (8), passé (3), degagé (3), développé (7), rond de jambe (3), grand battement (4), arm movements (1), forward stepping (3), turns (6), elevation work (28), falls (1), and dance-specific motor strategies (6). Several recurring themes emerged from these studies: that elite dancers demonstrate different and superior motor strategies than novices or nondancers; that dancers perform differently when using a barre as opposed to without a barre, both in terms of muscle activation patterns and weight shift strategies; that while skilled dancers tend to be more consistent across multiple trials of a task, considerable variability is seen among participants, even when matched for background, years of training, body type, and other variables; and that dance teachers recommend methods of achieving movement skills that are inconsistent with optimal biomechanical function, as well as inconsistent with strategies employed by elite dancers. Measurement tools and the efficacy of study methodologies are also discussed.

Dance Class Structure Affects Youth Physical Activity and Sedentary Behavior: A Study of Seven Dance Types.

PURPOSE: The study aims were to determine: (a) how class structure varies by dance type, (b) how moderate-to-vigorous physical activity (MVPA) and sedentary behavior vary by dance class segments, and (c) how class structure relates to total MVPA in dance classes. METHOD: Participants were 291 boys and girls ages 5 to 18 years old enrolled in 58 dance classes at 21 dance studios in Southern California. MVPA and sedentary behavior were assessed with accelerometry, with data aggregated to 15-s epochs. Percent and minutes of MVPA and sedentary behavior during dance class segments and percent of class time and minutes spent in each segment were calculated using Freedson age-specific cut points. Differences in MVPA (Freedson 3 Metabolic Equivalents of Tasks age-specific cut points) and sedentary behavior ( < 100 counts/min) were examined using mixed-effects linear regression. RESULTS: The length of each class segment was fairly consistent across dance types, with the exception that in ballet, more time was spent in technique as compared with private jazz/hip-hop classes and Latin-flamenco and less time was spent in routine/practice as compared with Latin-salsa/ballet folklorico. Segment type accounted for 17% of the variance in the proportion of the segment spent in MVPA. The proportion of the segment in MVPA was higher for routine/practice (44.2%) than for technique (34.7%). The proportion of the segment in sedentary behavior was lowest for routine/practice (22.8%). CONCLUSION: The structure of dance lessons can impact youths' physical activity. Working with instructors to increase time in routine/practice during dance classes could contribute to physical activity promotion in youth.

Electromyographic analysis of grand-plié in ballet and modern dancers.

PURPOSE: The purpose of this report is to describe lower extremity muscle activity in grand-plié, as determined by EMG analysis; to compare and contrast muscle function in grand-plié and demi-plié to support the hypothesis that grand-plié is not simply a deeper demi-plié, but rather a fundamentally different movement in terms of muscle use; and to present further evidence in support of the hypothesis that ballet dancers use muscles differently than modern dancers in dance movement. METHODS: Surface electromyography was used to analyze lower extremity muscle activity during grand-plié in first position with lower extremities turned out in five ballet and seven modern female professional dancers. RESULTS: Electromyographic (EMG) activity of tibialis anterior included continuous activity from heel-off during the lowering phase, through midcycle, and ending at heel-on during the rising phase in all grand-pliés; the majority of tibialis anterior EMG tracings in ballet dancers had additional activity at the end of the rising phase. All EMG tracings for vastus lateralis and medialis included a peak of activity during the lowering phase, a decrease (valley) at midcycle, followed by another peak during the rising phase; increased activity at the end of the rising phase was observed in most grand-plié in ballet, and not modern, dancers. Adductor EMG activity was also observed in all tracings with a peak during the lowering phase from heel-off to midcycle, a valley at midcycle, followed by a peak of activity in early rising phase; the midcycle valley was of lower, and the rising phase peak of higher, activity in ballet compared with modern dancers. Variation of EMG patterns was observed for lateral and medial gastrocnemius, gluteus maximus, and hamstrings. CONCLUSIONS: The data support the concept that lower extremity muscle activity in dance movement is comprised of three major types: (a) unique, characteristic activity required for the execution of the movement; (b) varied activity which is characteristic of dancers of different dance idioms; and (c) varied activity which may depend on factors such as balance, personal habit, and individual training background. Furthermore, EMG activity of vastus lateralis and medialis at the midcycle valley in grand-plié was significantly less in ballet dancers than in modern dancers despite similar degree of knee flexion, suggesting that ballet dancers may have lower patellofemoral joint reaction force at midcycle than modern dancers.

Physiological characteristics of elite dancers of different dance styles.

The present investigation was aimed to study international level dancesport dancer's aerobic capacity during incremental test and competition simulation in relation to the gender, dance style and international ranking. A total of 30 couples (12 Standard, 7 Latin American and 11 Ten Dance; aged 22.8 ± 6.6 years male and 22.0 ± 6.4 years female) performed an incremental treadmill test and competition simulation. In this study for the first time we carried out longer than one round competition simulation and compared three different dancesport styles (Standard, Latin American and Ten Dance). The results showed that dancers of these three dance styles had similar aerobic capacity values. The average maximal oxygen consumption (VO2max) values were 59.6 ± 5.1 and 51.2 ± 6.2 ml · min(-1) · kg(-1) for male and female dancers, respectively. Competition simulation showed that Latin American Dance discipline is physiologically more intensive compared to Standard and Ten Dance styles especially for the female dancers. It appeared that male and female Standard dancers tended to perform at lower intensity than anaerobic threshold (AT) during competition simulation (male 97.3 ± 2.9%; female 97.9 ± 3.6%), while Latin (male 101.4 ± 2.9%; female 106.7 ± 5.9%) and Ten Dance (male 100.7 ± 6.4%; female 99.2 ± 5.6%) competition intensity was higher compared to AT level of athletes. The highest heart rate during competition simulation was always found during the last dances (Paso Double, Jive or Quickstep) and in the last round of each dance style. No significant relationship between VO2max values and international rankings was registered.

Example-based automatic music-driven conventional dance motion synthesis.

We introduce a novel method for synthesizing dance motions that follow the emotions and contents of a piece of music. Our method employs a learning-based approach to model the music to motion mapping relationship embodied in example dance motions along with those motions' accompanying background music. A key step in our method is to train a music to motion matching quality rating function through learning the music to motion mapping relationship exhibited in synchronized music and dance motion data, which were captured from professional human dance performance. To generate an optimal sequence of dance motion segments to match with a piece of music, we introduce a constraint-based dynamic programming procedure. This procedure considers both music to motion matching quality and visual smoothness of a resultant dance motion sequence. We also introduce a two-way evaluation strategy, coupled with a GPU-based implementation, through which we can execute the dynamic programming process in parallel, resulting in significant speedup. To evaluate the effectiveness of our method, we quantitatively compare the dance motions synthesized by our method with motion synthesis results by several peer methods using the motions captured from professional human dancers' performance as the gold standard. We also conducted several medium-scale user studies to explore how perceptually our dance motion synthesis method can outperform existing methods in synthesizing dance motions to match with a piece of music. These user studies produced very positive results on our music-driven dance motion synthesis experiments for several Asian dance genres, confirming the advantages of our method.

Epidemiology of athletic injuries in classic ballet practitioners / Epidemiologia de lesiones musculoesqueleticas en practicantes de balé clásico / Epidemiologia de lesões musculoesqueléticas em praticantes de ballet clássico

Specific overloads of ballet practice may represent risk factors for injuries. The objective of this study was to analyze the epidemiology of typical injuries of ballet, including factors associated with history of injury in ballet practitioners. Studied subjects integrated 124 dancers, of both genders, from nine ballet schools from Campo Grande, Mato Grosso do Sul State, Brazil. To obtain information about injuries, we used a morbidity survey. Participants were divided into two groups: G1 (with injuries) and G2 (without injuries). In relation to prevalence of injuries, 89 cases were registered, and 61 dancers (49%) reported damages incidence, with record of 1.48 cases per practitioner. Moreover, the G2 presented higher body weight (G1: 51±8 versus G2: 55±10 kg) and training time (G1: 4.0±2.0 versus G2: 5.0±4.1 years). With respect to injury type, joints (32%) and muscle affections (25%) were the main occurrences in the lower limbs (85%) due to specific exercises (30%). Weekly exposure time was the most important mechanism to injury installation. The more important causal circumstance to injury occurrence was constituted by specific training (49%) and choreographic performance (41%). In conclusion, evidences have showed that joint injuries in lower limbs are the main classical ballet injuries in ballet practitioners, and weekly exposure time is the most important factor associated with injuries in classical ballet.

Demandas específicas de la práctica de balé pueden representar factores de riesgo para lesiones musculoesqueleticas. Eso estudio tuvo como objetivo analizar la epidemiologia de lesiones típicas del balé, con factores asociados a la historia de lesión en bailarines. Hubo la integración de 124 participantes de los dos géneros, procedentes de nueve escuelas de balé de Campo Grande, Mato Grosso do Sul, Brasil. Se utilizó una averiguación de morbidad referida para registrar las lesiones. Los participantes fueron distribuidos en dos grupos: G1, sin lesión, y G2, con lesión. Con relación a la presencia de lesión, se registraron 89 casos, y 61 bailarines (un 49%) reportaron lesiones con registro de 1,48 casos por practicante. El G2 presentó mayor masa corporal (G1: 51±8 versus G2: 55±10 kg) y tiempo de entrenamiento (G1: 4,0±2,0 versus G2: 5,0±4,1 años). Hubo predominancia de lesiones articulares (32%) y musculares (25%) en las extremidades inferiores (85%) originarias de ejercicios específicos (30%). El mayor tiempo semanal de práctica se configuró como el principal factor de riesgo para lesión. La circunstancia que más causó lesiones fue el entrenamiento específico (49%), seguido por el ensayo de coreografía (41%). Se concluso que las lesiones articulares en extremidades inferiores son las principales lesiones del balé clásico, y el tiempo semanal de exposición se constituye el principal factor asociado a las lesiones en el balé clásico.

Demandas específicas da prática de ballet podem representar fatores de risco para lesões musculoesqueléticas. Este estudo teve por objetivo analisar a epidemiologia das lesões típicas do ballet, com fatores associados ao histórico de lesão em bailarinos. A casuística integrou 124 participantes de ambos os sexos, procedentes de nove escolas e companhias de ballet de Campo Grande, no Mato Grosso do Sul. Para registro de lesões, utilizou-se um inquérito de morbidade referida. Os participantes foram distribuídos em dois grupos: G1, sem lesão, e G2, com lesão. Em relação à presença de lesão, foram registrados 89 casos, sendo que 61 bailarinos (49%) relataram terem se lesionado, com registro de 1,48 casos por praticante. O G2 apresentou maior massa corporal (G1: 51±8 versus G2: 55±10 kg) e tempo de treinamento (G1: 4,0±2,0 versus G2: 5,0±4,1 anos). Houve predomínio de lesões articulares (32%) e musculares (25%) nos membros inferiores (85%), decorrentes de exercícios específicos (30%). O maior tempo semanal de prática configurou o principal fator de risco para lesão. A circunstância que mais provocou lesões foi o treino específico (49%), seguido pelo ensaio de coreografia (41%). Conclui-se que as lesões articulares em membros inferiores são as principais lesões do ballet clássico, e o tempo semanal de exposição constitui o principal fator associado a lesões no ballet clássico.

Case report. Paraphimosis due to erotic dancing.

Paraphimosis usually develops when a tight foreskin is retracted over the glans penis for a prolonged period. Many esoteric aetiologies have been implicated in the development of paraphimosis including piercing the foreskin, Plasmodium falciparum infection, application of celadine juice to the foreskin, chancroid, pessaries and the implantation of pearls. We report the first two cases of paraphimosis developing during wining, an erotic dance native to Trinidad & Tobago.