Description

Each issue focuses on bringing you the current results of clinical and experimental research. The aim of the Journal of Dance Medicine & Science is to provide you with one source for up-to-date information. Featured articles are drawn from the fields of:

Publications in this journal

• Effects of voice enhancement technology and relaxing music on the frequency of imagery among break dancers.

  Authors: Costas I Karageorghis, Danielle L Smith, David-Lee Priest

  Journal of dance medicine & science : official publication of the International Association for Dance Medicine & Science. 16(1):8-16.

  A device was developed in 2008 by Hypnoke International Ltd. for use by performance consultants and hypnotherapists. It enhances a practitioner's voice and blocks out auditory distractions whileA device was developed in 2008 by Hypnoke International Ltd. for use by performance consultants and hypnotherapists. It enhances a practitioner's voice and blocks out auditory distractions while delivering imagery inductions, thereby increasing their effectiveness. This study examined the impact of voice-enhancement technology and relaxing music on the frequency of imagery experienced by a sample of elite British break dancers (N = 20; mean age = 26.5 years, SD = 1.5 years). An imagery script was administered to participants under four conditions: voice enhancement with music, voice enhancement only, a music-only control, and a no-voice-enhancement-and-no-music control. Frequency of imagery was assessed using the Sport Imagery Questionnaire. There was a higher incidence of imagery in the voice enhancement with music, voice enhancement only, and music-only conditions when compared to the no-voice-enhancement-and-no-music control. The key finding was that imagery was most frequent when voice enhancement was combined with music in a complementary manner. Thus, it is concluded that the use of voice enhancement technology can improve the efficacy of relaxation and imagery training for break dancers, and potentially, dancers in general.

• Differences in Segmental Coordination and Postural Control in a Multi-joint Dance Movement: Développé Arabesque.

  Authors: Shaw Bronner

  Journal of dance medicine & science : official publication of the International Association for Dance Medicine & Science. 16(1):26-35.

  Analysis of skill at multiple points on the learning continuum provides insight into how complex limb and postural organization is modified with extended practice. Dancers at three skill levels wereAnalysis of skill at multiple points on the learning continuum provides insight into how complex limb and postural organization is modified with extended practice. Dancers at three skill levels were compared performing a domain-specific movement (développé arabesque) to identify motor control parameters underlying skill acquisition of a sequential multi-joint trunk and extremity movement. It was hypothesized that general organization would be similar between groups, but that segmental coordination and postural control would differ with skill level. Twenty-seven expert, advanced, and intermediate dancers performed six repetitions of an arabesque sequence with the right limb. Data were acquired with a five-camera motion analysis system. Differences between groups in pelvis and gesture limb displacement, joint coordination patterns, and variability were determined using ANOVA with post hoc comparisons where applicable. Subjects displayed similar movement organization and timing. Differences were found in postural pelvic control and intra- and inter-limb coordination. These differences were most apparent during the arabesque phase. Control of the pelvis appears to be a key area that requires prolonged practice to master.

• A kinematic approach to calculating ground reaction forces in dance.

  Authors: James Shippen, Barbara May

  Journal of dance medicine & science : official publication of the International Association for Dance Medicine & Science. 16(1):39-43.

  A technique that can be used with dancers for the calculation of ground reaction forces in the absence of force plates is described. The ground reaction forces are required for analyzing potentiallyA technique that can be used with dancers for the calculation of ground reaction forces in the absence of force plates is described. The ground reaction forces are required for analyzing potentially injurious activity within the dancer's body. However, the use of a force plate for this purpose disrupts the performance surface and could, due to its stiffness, in itself lead to injury. This technical report provides an indication that a technique utilizing kinematic calculations of ground reaction forces in dancers offers a viable alternative. The kinematic calculations technique is suitable for use across large performance surfaces, including sprung floors. In this preliminary study, it is validated against force plate output using data from a single dancer and is extended to consider tuning of the generic mass distribution model to improve accuracy in the calculation of ground reaction forces.

• Upper-body muscular endurance in female university-level modern dancers: a pilot study.

  Authors: Jatin P Ambegaonkar, Shane V Caswell, Jason B Winchester, Amanda A Caswell, Matthew J Andre

  Journal of dance medicine & science : official publication of the International Association for Dance Medicine & Science. 16(1):3-7.

  Physical demands vary among dance styles, and injury patterns differ accordingly. Modern dance tends to be high in upper-body demands, and university-level female modern dancers are suggested to bePhysical demands vary among dance styles, and injury patterns differ accordingly. Modern dance tends to be high in upper-body demands, and university-level female modern dancers are suggested to be at high risk for upper-body injury. Low muscular endurance is a known injury risk factor. Whether modern dancers have different upper-body muscular endurance than non-dancers is unclear. Thus, the purpose of this study was to compare upper-body endurance in female university-level modern dancers (n = 17) and physically active non-dancers (n = 15), using the modified push-up test. Pearson-correlations examined relationships between anthropometrics and push-ups. Multiple regression analyses were used to determine whether anthropometrics and physical activity could predict push-up scores. One-way ANOVAs compared upper-body endurance (number of push-ups) and physical activity between groups (p < 0.05). Except for height (r = -.37), no variables were related to push-ups. Neither anthropometrics nor physical activity were able to predict push-up scores (p = 0.25). Despite dancers being more active/day (3.6 ± 1.9 vs. 0.9 ± 0.4 hrs/day, p < 0.001), more times per week (5.4 ± 1.2 vs. 4.0 ± 1.8, p = 0.02), and having greater overall physical activity volumes (20.4 ± 11.4 vs. 3.3 ± 2.5 hrs/week, p < 0.001) than non-dancers, both groups had similar upper-body endurance (22.2 ± 8.6 vs. 19.9 ± 8.2, p = 0.44). A probable explanation for this similarity exists in the lack of physical activity beyond dance itself performed by the dancers; our preliminary work suggests that modern dance alone may not produce upper-body muscle endurance gains. Hence, it is suggested that modern dancers should engage in strength and conditioning training programs to enhance upper-body endurance.

• Injuries in professional modern dancers: incidence, risk factors, and management.

  Authors: Selina Shah, David S Weiss, Raoul J Burchette

  Journal of dance medicine & science : official publication of the International Association for Dance Medicine & Science. 16(1):17-25.

  Modern (or contemporary) dance has become increasingly popular, yet little has been reported with respect to modern dance injuries and their consequences. The purpose of this study is to define theModern (or contemporary) dance has become increasingly popular, yet little has been reported with respect to modern dance injuries and their consequences. The purpose of this study is to define the incidence, risk factors, and management of musculoskeletal injuries in professional modern dancers. A total of 184 dancers in the United States completed an anonymous 17-page questionnaire on their injuries, including extensive details regarding the two most severe injuries that had occurred in the prior 12 months. According to their self-reports, a total of 82% of the dancers had suffered between one and seven injuries. The foot and ankle (40%) was the most common site of injury, followed by the lower back (17%) and the knee (16%). The rate of injuries was 0.59 per 1,000 hours of class and rehearsal. Injured male dancers returned to full dancing after a median of 21 days, while females returned after a median of 18 days. Most dancers missed no performances due to injury. Of the medical consultations sought by dancers for their injuries, 47% were made to physicians, 41% to physical therapists, and 34% to chiropractors. The majority of dancers adhered to the advice given them by consultants (87% of males and 78% of females for the most severe injury). While the majority of injuries were considered work-related (61% of the most severe injury and 69% of the second most severe), few were covered by Workers' Compensation insurance (12% and 5% respectively). These professional modern dancers suffer from a rate of injury similar to other groups of professional dancers. Most dancers return to a partial level of dancing several weeks before attempting full-capacity dancing.

• Effects of kinesthetic versus visual imagery practice on two technical dance movements: a pilot study.

  Authors: Elizabeth Coker Girón, Tara McIsaac, Dawn Nilsen

  Journal of dance medicine & science : official publication of the International Association for Dance Medicine & Science. 16(1):36-8.

  Motor imagery is a type of mental practice that involves imagining the body performing a movement in the absence of motor output. Dance training traditionally incorporates mental practice techniques,Motor imagery is a type of mental practice that involves imagining the body performing a movement in the absence of motor output. Dance training traditionally incorporates mental practice techniques, but quantitative effects of motor imagery on the performance of dance movements are largely unknown. This pilot study compared the effects of two different imagery modalities, external visual imagery and kinesthetic imagery, on pelvis and hip kinematics during two technical dance movements, plié and sauté. Each of three female dance students (mean age = 19.7 years, mean years of training = 10.7) was assigned to use a type of imagery practice: visual imagery, kinesthetic imagery, or no imagery. Effects of motor imagery on peak external hip rotation varied by both modality and task. Kinesthetic imagery increased peak external hip rotation for pliés, while visual imagery increased peak external hip rotation for sautés. Findings suggest that the success of motor imagery in improving performance may be task-specific. Dancers may benefit from matching imagery modality to technical tasks in order to improve alignment and thereby avoid chronic injury.

• Perceived autonomy support, motivation regulations and the self-evaluative tendencies of student dancers.

  Authors: Eleanor Quested, Joan L Duda

  Journal of dance medicine & science : official publication of the International Association for Dance Medicine & Science. 15(1):3-14.

  Limited research has considered the social-environmental and motivational processes predictive of self evaluations and body-related concerns. Evidence suggests that low self-esteem, poor bodyLimited research has considered the social-environmental and motivational processes predictive of self evaluations and body-related concerns. Evidence suggests that low self-esteem, poor body evaluations, and associated anxieties are particularly prevalent among the student dance population. Grounded in self-determination theory (SDT), this study examined the relationships among perceptions of autonomy support, motivation regulations, and self-evaluations of body-related concerns in the context of vocational dance. Three hundred and ninety-two dancers completed questionnaires regarding their perceptions of autonomy support in their dance school, reasons for engaging in dance, self-esteem, social physique anxiety (SPA), and body dissatisfaction. Structural equation modeling analyses revealed that perceived autonomy support predicted intrinsic motivation (+) and amotivation (-). Extrinsic regulation positively predicted SPA. Amotivation mediated the associations between perceptions of autonomy support and dancers' self-esteem, SPA, and body dissatisfaction. The utility of SDT in understanding predictors of self-worth, physical evaluations, and associated concerns was supported. Moreover, this study provides preliminary evidence supporting the applicability of SDT in dance contexts.

• Pelvis and hip three-dimensional kinematics in grand battement movements.

  Authors: Shaw Bronner, Sheyi Ojofeitimi

  Journal of dance medicine & science : official publication of the International Association for Dance Medicine & Science. 15(1):23-30.

  Dancers frequently sustain hip injuries, including labral tears, coxa saltans, stress fractures, tendinosis, and joint disease. High velocity kicks (grand battement), with extreme abduction andDancers frequently sustain hip injuries, including labral tears, coxa saltans, stress fractures, tendinosis, and joint disease. High velocity kicks (grand battement), with extreme abduction and external rotation (ER), may stress the hip, sacroiliac joint, and surrounding soft tissue. However, three-dimensional kinematic dance descriptions are limited. The purpose of this study was to describe the kinematics of the pelvis and hip in grand battement movements in healthy dancers. Seventeen advanced-level college dancers performed three battement conditions: battement devant to the front, à la seconde to the side, and derrière to the back. Data were collected with a 5-camera motion capture system. Repeated measures ANOVA (p < 0.05) compared peak pelvis and hip angular displacement and hip and toe velocity for all conditions and planes. Three-dimensional hip to pelvic ratios were calculated. There were differences in pelvic angular displacement between conditions in all planes (p < 0.00). Battement devant posterior pelvic tilt exceeded that of battement seconde. Both were opposite in direction from the anterior pelvic tilt of battement derrière. All conditions demonstrated pelvic obliquity toward the stance limb, with battement derrière greater than devant and seconde. Battement derrière transverse plane pelvic displacement exceeded that found in devant and seconde. There were also differences in hip angular displacement between conditions in all planes (p < 0.00). Battement derrière hip extension differed from battement devant and seconde flexion. The hip abducted in all conditions, with battement seconde exceeding devant and derrière. In the transverse plane, the hip rotated internally in battement seconde and externally in battement derrière and devant. In battement devant and seconde, peak hip ER decreased relative to baseline, while increasing at the peak of battement derrière. Battement peak velocities were relatively low. The ratio of hip to pelvic angular sagittal plane motion was 4.1, 2.6, and 0.5 in battement devant, seconde, and derrière respectively; 0.9, 2.6, and 1.5 in the frontal plane; and 0.6, 8.5, and 0.2 in the transverse plane. This confirms that pelvic motion provides a large proportion of the battement movement.

• Case studies in cervicothoracic spine function evaluation and treatment of two dancers with mechanical neck pain.

  Authors: Emily Sandow

  Journal of dance medicine & science : official publication of the International Association for Dance Medicine & Science. 15(1):37-44.

  It has been reported that manual therapy directed at the thoracic spine followed by exercise may improve outcomes in patients with mechanical neck pain. At this point, there is little available dataIt has been reported that manual therapy directed at the thoracic spine followed by exercise may improve outcomes in patients with mechanical neck pain. At this point, there is little available data on dancers with neck pain, and it is unclear whether this type of treatment is appropriate for restoring the rigorous level of activity required of the dancer. The purpose of this study was to review the evaluation, clinical decision-making process, and treatment of two dancers-one with acute and the other with chronic neck pain-who fell into the classification of patients who might benefit from an intervention to the thoracic spine. The two participants were a musical theater dancer with an acute onset of neck pain and a retired dancer who was an active dance company director with an 11-year history of chronic neck pain. Both participants went through a standard examination and were treated with mobilizations to the upper thoracic spine followed by therapeutic exercises. In both cases, successful outcomes were achieved immediately after treatment and up to six months after discharge from physical therapy.

• Ground reaction forces in ballet dancers landing in flat shoes versus pointe shoes.

  Authors: Heather L Walter, Carrie L Docherty, John Schrader

  Journal of dance medicine & science : official publication of the International Association for Dance Medicine & Science. 15(2):61-4.

  Reports in the literature suggest an abundance of lower extremity injuries in ballet dancers; however, few studies have identified the underlying causes of these injuries. Excessive ground reactionReports in the literature suggest an abundance of lower extremity injuries in ballet dancers; however, few studies have identified the underlying causes of these injuries. Excessive ground reaction forces and shoe type are two potential contributing factors. Eighteen collegiate female ballet majors volunteered for this study. Each participant performed 12 trials of a basic ballet jump, six trials in flat shoes and 6 trials in pointe shoes, landing on a force plate. Ground reaction force (Newtons) and jump height (centimeters) were assessed for each trial. The mean ground reaction force and jump height for each shoe condition was used for statistical analysis. Two dependent t-tests were conducted to determine differences between the shoe types, one for ground reaction force and one for jump height. Alpha level was set at p < .05. We found that the ground reaction force was significantly higher when landing in flat shoes than in pointe shoes (p = .003). There was no significant difference in jump height between the two shoe conditions. This leads us to believe that the increase in ground reaction force was produced primarily by the shoe type.

• Injury, imagery, and self-esteem in dance healthy minds in injured bodies?

  Authors: Sanna M Nordin-Bates, Imogen J Walker, Jo Baker, Jocelyn Garner, Cinzia Hardy, Sarah Irvine, Corinne Jola, Helen Laws, Peta Blevins

  Journal of dance medicine & science : official publication of the International Association for Dance Medicine & Science. 15(2):76-85.

  The purpose of this study was to investigate a selection of psychological variables (help-seeking behaviors, mental imagery, self-esteem) in relation to injury among UK dancers. We recruited 216The purpose of this study was to investigate a selection of psychological variables (help-seeking behaviors, mental imagery, self-esteem) in relation to injury among UK dancers. We recruited 216 participants from eight dance styles and six levels of involvement. It was found that 83.5% of the participants had experienced at least one injury in the past year. The most common response to injury was to inform someone, and most continued to dance when injured, albeit carefully. Physical therapy was the most common treatment sought when an injury occurred (38.1%), and dancers seemed to follow recommendations offered. Injured and non-injured dancers did not differ in their imagery frequencies (facilitative, debilitative, or injury-related) and scored similarly (and relatively high) in self-esteem. Neither facilitative nor debilitative imagery was correlated with self-esteem, but dancers who engaged in more facilitative imagery in general also reported doing so when injured. Altogether, it appears that injury is not related to dancers' self-esteem or imagery, at least not when injuries are mild or moderate. Even so, such conclusions should be made with caution, given that most dancers do sustain at least one injury each year.

• The impact of mirrors on body image and performance in high and low performing female ballet students.

  Authors: Sally A Radell, Daniel D Adame, Steven P Cole, Nicole J Blumenkehl

  Journal of dance medicine & science : official publication of the International Association for Dance Medicine & Science. 15(3):108-15.

  This study assesses the effect of mirrors on body image and performance in high and low performing female collegiate ballet students. Twenty-three females enrolled in a beginning ballet class wereThis study assesses the effect of mirrors on body image and performance in high and low performing female collegiate ballet students. Twenty-three females enrolled in a beginning ballet class were taught using mirrors, and a second group of 23 beginning females were taught without mirrors. All participants completed the Cash 69-item Body Self-Relations Questionnaire during the first and last class of a 14-week semester. They were videotaped performing in the studio during the fifth and fourteenth weeks. Two ballet teachers independently viewed the videotapes to evaluate the dancers' rhythmic accuracy, ease and flow of movement, and mastery of steps and alignment, and rated the students' skill level on a 1-5 scale. For analysis purposes, students whose scores averaged three or higher were categorized as "high performers," and those who averaged less than three were "low performers." Two (mirror, non-mirror) by two (high performance, low performance) by two (pre-test, post-test) repeated measures ANOVAs were used to test class differences over the course of the semester. There were significant 3-way interactions for overweight preoccupation (p < 0.01) and body-areas satisfaction (p < 0.05). Low performers increased in overweight preoccupation in the non-mirror class while decreasing in the mirror class. High performers significantly increased in satisfaction for most areas of their body in the non-mirror class, while there were smaller increases for both low and high performers in the mirror class. It is concluded that while use of the mirror has some benefits in training, higher performing dancers feel better about their body image when they do not use the mirror. Lower performers who use the mirror worry less about their weight; those who do not use the mirror worry more. The mirror may provide feedback that helps low performing dancers feel more comfortable with their weight.

• Development, validity, and reliability of a ballet-specific aerobic fitness test.

  Authors: Emily Twitchett, Alan Nevill, Manuela Angioi, Yiannis Koutedakis, Matthew Wyon

  Journal of dance medicine & science : official publication of the International Association for Dance Medicine & Science. 15(3):123-7.

  The aim of this study was to develop and assess the reliability and validity of a multi-stage, ballet-specific aerobic fitness test to be used in a dance studio setting. The test consists of fiveThe aim of this study was to develop and assess the reliability and validity of a multi-stage, ballet-specific aerobic fitness test to be used in a dance studio setting. The test consists of five stages, each four minutes long, that increase in intensity. It uses classical ballet movement of an intermediate-level of difficulty, thus emphasizing physiological demand rather than skill. The demand of each stage was determined by calculating the mean oxygen uptake during its final minute using a portable gas analyser. After an initial familiarization period, eight female subjects performed the test twice within seven days. The results showed significant differences in oxygen consumption between stages (p < 0.001), but not between trials. Pearson correlation co-efficients produced a very good linear relationship between trials (r = 0.998, p < 0.001). Bland-Altman reliability analysis revealed the 95% limits of agreement to be ± 6.2 ml·kg(-1)·min(-1), showing good agreement between trials. The oxygen uptake in our subjects equated positively to previous estimates for class and performance, confirming validity. It was concluded that the test is suitable for use among classical ballet dancers, with many possible applications.

• Follow-up study to "The effect of sprung (suspended) floors on leg stiffness during grand jeté landings in ballet".

  Authors: James Hackney, Sara Brummel, Dana Becker, Aubrey Chenoweth, Sandra Koons, Meredith Stewart

  Journal of dance medicine & science : official publication of the International Association for Dance Medicine & Science. 15(3):134-5.

• A within-subject analysis of the effects of remote cueing on pelvic alignment in dancers.

  Authors: Kimberly M Holt, Thomas M Welsh, Jaclyn Speights

  Journal of dance medicine & science : official publication of the International Association for Dance Medicine & Science. 15(1):15-22.

  Many professionals who treat and train dancers believe that good alignment at the pelvis can facilitate movement efficiency and reduce injury risk in a variety of dance genres. This study evaluatedMany professionals who treat and train dancers believe that good alignment at the pelvis can facilitate movement efficiency and reduce injury risk in a variety of dance genres. This study evaluated the effects of a remote cueing technique on pelvic alignment for dancers in a university-based professional training program. Two female dancers participated in 20-minute individualized observation and training sessions twice a week for eight weeks. Pelvic alignment improved to criterion levels for both dancers, suggesting that individualized approaches may have special utility in training dancers.

• Bone mineral density and body composition of collegiate modern dancers.

  Authors: Karlie J Friesen, Ralph Rozenek, Karen Clippinger, Kathy Gunter, Albert C Russo, Susan E Sklar

  Journal of dance medicine & science : official publication of the International Association for Dance Medicine & Science. 15(1):31-6.

  This study investigates body composition (BC), bone mineral density (BMD), eating behaviors, and menstrual dysfunction in collegiate modern dancers. Thirty-one female collegiate modern dance majorsThis study investigates body composition (BC), bone mineral density (BMD), eating behaviors, and menstrual dysfunction in collegiate modern dancers. Thirty-one female collegiate modern dance majors (D), 18 to 25 years of age, and 30 age-matched controls (C) participated in the study. BC and BMD were measured using dual energy x-ray absorptiometry (DXA). Upper and lower body strength was assessed by chest and leg press one-repetition maximum tests. Participants completed three-day food records, and the diet was analyzed using nutritional software. Menstrual dysfunction (MD) and history of eating disorder (ED) data were collected via questionnaires. BC and BMD variables were analyzed using MANCOVA and frequency of ED and MD by Chi-Square analysis. BMD was greater in D than C at the spine (1.302 ± 0.135 g/cm(2) vs. 1.245 ± 0.098 g/cm(2)), and both the right hip (1.163 ± 0.111 g/cm(2) vs. 1.099 ± 0.106 g/cm(2)) and left hip (1.160 ± 0.114 g/cm(2) vs. 1.101 ± 0.104 g/cm(2); p ≤ 0.05). Total body fat percentage was lower in D than C (25.9 ± 4.2% vs. 32.0 ± 5.9%; p ≤ 0.05), and percent of fat distributed in the android region was also lower in D than C (28.0 ± 6.2% vs. 37.6 ± 8.6%; p ≤ 0.05). With regard to diet composition, only percent fat intake was lower in D than C (27.54 ± 6.8% vs. 31.5 ± 7.4%, p ≤ 0.05). A greater incidence of ED was reported by D than C (12.9% vs. 0%; p ≤ 0.05), as well as a greater incidence of secondary amenorrhea (41.9% vs 13.3%; p ≤ 0.05). No differences were found for incidence of primary amenorrhea, oligomenorrhea, or use of birth control. Strength values were higher in D than C for both chest press (30.1 ± 0.9 kg vs. 28.4 ± 1.0 kg; p ≤ 0.05) and leg press (170.7 ± 4.2 kg vs.163.1 ± 3.9 kg; p ≤ 0.05). It is concluded that the dancers in our study had a healthy body weight, yet reported a higher incidence of eating disorders and menstrual dysfunction, than non-dancers. These dancers' higher BMD may be attributable to the mechanical loading and increased strength associated with practicing modern dance. Further, modern dancers had lower centrally located body fat, which decreases the risk for cardiovascular and metabolic diseases.

• The effects of nutrition, puberty and dancing on bone density in adolescent ballet dancers.

  Authors: Peter Burckhardt, Emma Wynn, Marc-Antoine Krieg, Carlo Bagutti, Mohamed Faouzi

  Journal of dance medicine & science : official publication of the International Association for Dance Medicine & Science. 15(2):51-60.

  Ballet dancers have on average a low bone mineral content (BMC), with elevated fracture-risk, low body mass index (BMI) for age (body mass index, kg/m2), low energy intake, and delayed puberty. ThisBallet dancers have on average a low bone mineral content (BMC), with elevated fracture-risk, low body mass index (BMI) for age (body mass index, kg/m2), low energy intake, and delayed puberty. This study aims at a better understanding of the interactions of these factors, especially with regard to nutrition. During a competition for pre-professional dancers we examined 127 female participants (60 Asians, 67 Caucasians). They averaged 16.7 years of age, started dancing at 5.8 years, and danced 22 hours/week. Assessments were made for BMI, BMC (DXA), and bone mineral apparent density (BMAD) at the lumbar spine and femoral neck, pubertal stage (Tanner score), and nutritional status (EAT-40 questionnaire and a qualitative three-day dietary record). BMI for age was found to be normal in only 42.5% of the dancers, while 15.7% had a more or less severe degree of thinness (12.6% Grade2 and 3.1% Grade 3 thinness). Menarche was late (13.9 years, range 11 to 16.8 years). Food intake, evaluated by number of consumed food portions, was below the recommendations for a normally active population in all food groups except animal proteins, where the intake was more than twice the recommended amount. In this population, with low BMI and intense exercise, BMC was low and associated with nutritional factors; dairy products had a positive and non-dairy proteins a negative influence. A positive correlation between BMAD and years since menarche confirmed the importance of exposure to estrogens and the negative impact of delayed puberty. Because of this and the probable negative influence of a high intake of non-dairy proteins, such as meat, fish, and eggs, and the positive association with a high dairy intake, ballet schools should promote balanced diets and normal weight and should recognize and help dancers avoid eating disorders and delayed puberty caused by extensive dancing and inadequate nutrition.

• Development and evaluation of an educational intervention program for pre-professional adolescent ballet dancers: nutrition for optimal performance.

  Authors: Ashley F Doyle-Lucas, Brenda M Davy

  Journal of dance medicine & science : official publication of the International Association for Dance Medicine & Science. 15(2):65-75.

  The purpose of this investigation was to develop, implement, and evaluate a theoretically based nutritional education intervention through a DVD lecture series (three 30-minute classes) in summerThe purpose of this investigation was to develop, implement, and evaluate a theoretically based nutritional education intervention through a DVD lecture series (three 30-minute classes) in summer intensive programs for pre-professional, adolescent ballet dancers. Objectives of this intervention program were to increase knowledge of basic sports nutrition principles and the Female Athlete Triad and promote self-efficacy for adopting healthier dietary habits. Dancers ranging from 13 to 18 years old who were attending summer intensive programs affiliated with professional ballet companies were recruited. Group One (n = 231) participated in the nutrition education program, while Group Two the control participants (n = 90) did not. Assessments of the participants' dietary status consisted of a demographic questionnaire, a Sports Nutrition Knowledge and Behavior Questionnaire, and a Food Frequency Questionnaire. The intervention group was assessed at baseline, immediately post-program, and at six weeks post-program. The control group was assessed at baseline and at six weeks post-baseline. The intervention program was effective at increasing nutrition knowledge, perceived susceptibility to the Female Athlete Triad, and self-efficacy constructs. Improvements in dietary intake were also observed among intervention group participants. To improve overall health and performance nutrition education should be incorporated into the training regimens of adolescent dancers. This potentially replicable DVD-based program may be an effective, low-cost mechanism for doing that.

• Effect of footwear on dancers: a systematic review.

  Authors: Alycia Fong Yan, Claire Hiller, Richard Smith, Benedicte Vanwanseele

  Journal of dance medicine & science : official publication of the International Association for Dance Medicine & Science. 15(2):86-92.

  Dancers need their feet to be healthy and pain-free; therefore, the footwear they use is of great importance. Footwear has the potential to enhance or restrict movement and impact the dancer's bodyDancers need their feet to be healthy and pain-free; therefore, the footwear they use is of great importance. Footwear has the potential to enhance or restrict movement and impact the dancer's body in various ways. To evaluate the effects of footwear on dancers, in particular the effects on foot motion and injury during dance movements, we undertook a systematic review of the literature. The major databases were searched for articles on theatrical dance styles and dance footwear. Sixteen articles were selected for inclusion in this study, ten on ballet and the remainder covering a variety of other genres. The contribution of dance shoes to the quality of dance movement is a relatively unexplored subject; little experimental research has been done. Prospective scientific evidence is needed to support or disprove traditional beliefs regarding the effects of footwear on dance performance and dancers' health.

• Vitamin D status and musculoskeletal health in adolescent male ballet dancers a pilot study.

  Authors: Gaele Ducher, S Kukuljan, B Hill, A P Garnham, C A Nowson, M G Kimlin, J Cook

  Journal of dance medicine & science : official publication of the International Association for Dance Medicine & Science. 15(3):99-107.

  Adequate vitamin D levels during growth are critical to ensuring optimal bone development. Vitamin D synthesis requires sun exposure; thus, athletes engaged in indoor activities such as balletAdequate vitamin D levels during growth are critical to ensuring optimal bone development. Vitamin D synthesis requires sun exposure; thus, athletes engaged in indoor activities such as ballet dancing may be at relatively high risk of vitamin D insufficiency. The objective of this study was to investigate the prevalence of low vitamin D levels in young male ballet dancers and its impact on musculoskeletal health. Eighteen male ballet dancers, aged 10 to 19 years and training for at least 6 hours per week, were recruited from the Australian Ballet School, Melbourne, Australia. Serum 25(OH)D and intact PTH were measured in winter (July) from a non-fasting blood sample. Pubertal stage was determined using self-assessed Tanner criteria. Body composition and areal bone mineral density (aBMD) at the whole body and lumbar spine were measured using dual-energy x-ray absorptiometry (DXA). Injury history and physical activity levels were assessed by questionnaire. Blood samples were obtained from 16 participants. Serum 25(OH)D levels ranged from 20.8 to 94.3 nmol/L, with a group mean of 50.5 nmol/L. Two participants (12.5%) showed vitamin D deficiency [serum 25(OH)D level < 25 nmol/L], seven dancers (44%) had vitamin D insufficiency (25 to 50 nmol/L), and the remaining seven dancers (44%) had normal levels (> 50 nmol/L). No relationship was found between vitamin D status, PTH levels, body composition, and aBMD. The most commonly reported injuries were muscle tears and back pain. The average number of injuries reported by each dancer was 1.9 ± 0.4 (range: 0 to 5). There was no difference in the frequency of reported injuries between subjects with vitamin D deficiency or insufficiency (2.1 ± 0.6 injuries) and those with normal vitamin D levels (1.4 ± 0.6 injuries). This pilot study showed that more than half of highly-trained young male ballet dancers presented with low levels of vitamin D in winter. Further investigations in larger samples of adolescent athletes are needed to determine if this could negatively impact bone growth and place them at higher risk for musculoskeletal injuries.

• Injuries in a modern dance company effect of comprehensive management on injury incidence and cost.

  Authors: Sheyi Ojofeitimi, Shaw Bronner

  Journal of dance medicine & science : official publication of the International Association for Dance Medicine & Science. 15(3):116-22.

  Injury costs strain the finances of many dance companies. The objectives of this study were to analyze the effect of comprehensive management on injury patterns, incidence, and time loss and examineInjury costs strain the finances of many dance companies. The objectives of this study were to analyze the effect of comprehensive management on injury patterns, incidence, and time loss and examine its financial impact on workers compensation premiums in a modern dance company. In this retrospective-prospective cohort study, injury was defined as any physical insult that required financial outlay (workers compensation or self insurance) or caused a dancer to cease dancing beyond the day of injury (time-loss injury). Injury data and insurance premiums were analyzed over an eight-year period. Injuries were compared using a mixed linear model with phase and gender as fixed effects. It was found that comprehensive management resulted in 34% decline in total injury incidence, 66% decrease in workers compensation claims, and 56% decrease in lost days. These outcomes achieved substantial savings in workers compensation premiums. Thus, this study demonstrates the effectiveness of an injury prevention program in reducing injury-related costs and promoting dancers' health and wellness in a modern dance company.

• The effect of sprung (suspended) floors on leg stiffness during grand jeté landings in ballet.

  Authors: James Hackney, Sara Brummel, Kara Jungblut, Carissa Edge

  Journal of dance medicine & science : official publication of the International Association for Dance Medicine & Science. 15(3):128-33.

  This study compared stiffness of the landing leg in ballet dancers performing grand jeté on a sprung floor to leg stiffness during the same movement on a hard floor (wood on concrete). Leg stiffnessThis study compared stiffness of the landing leg in ballet dancers performing grand jeté on a sprung floor to leg stiffness during the same movement on a hard floor (wood on concrete). Leg stiffness was calculated as the ratio of vertical ground reaction force (in Newtons) to compression of the lower limb (in meters). Thirteen female dancers were measured for five repetitions each at the point of maximum leg compression while landing grand jeté on both of the surfaces, such that 20 milliseconds of data were represented for each trial. The stiffness of the landing leg at the point of maximum compression was decreased by a mean difference score of 6168.0 N/m ± 11,519.5 N/m on the hard floor compared to the sprung floor. Paired t-test yielded a one-tailed probability of p = 0.038. This effect was seen in 11 of the 13 participants. The finding of increased stiffness of the landing leg in the sprung floor condition suggests that some of the force of landing the leap was absorbed by the surface, and therefore did not need to be absorbed by the landing leg itself. This in turn implies that a sprung dance floor may help to prevent dance-related injuries.

• The use of stabilization exercises and movement reeducation to manage pain and improve function in a dancer with focal degenerative joint disease of the spine.

  Authors: Marshall Hagins

  Journal of dance medicine & science : official publication of the International Association for Dance Medicine & Science. 15(3):136-42.

  Little has been written about rehabilitation of low back pain (LBP) specific to the professional dancer. However, there is a rapidly increasing amount of rehabilitation research related to the careLittle has been written about rehabilitation of low back pain (LBP) specific to the professional dancer. However, there is a rapidly increasing amount of rehabilitation research related to the care of LBP in the general population that may be applied to the dancer population. The purpose of this case report is to describe the physical therapy management of a 37-year-old female professional dancer with a 5-year history of spinal pain and loss of function in the presence of degenerative joint disease at a single segment (T12-L1). Patient interventions focused on stabilization exercises and movement reeducation. The dancer returned to limited dance performance at 6 weeks. At 5 months she had returned to complete dance function, with pain and functional (Oswestry) levels improved from initial values of 7/10 and 48%, respectively, to 1/10 and 26%.

• Lower extremity kinetics in tap dance.

  Authors: Lester Mayers, Shaw Bronner, Sujani Agraharasamakulam, Sheyi Ojofeitimi

  Journal of dance medicine & science : official publication of the International Association for Dance Medicine & Science. 14(1):3-10.

  Tap dance is a unique performing art utilizing the lower extremities as percussion instruments. In a previous study these authors reported decreased injury prevalence among tap dancers compared toTap dance is a unique performing art utilizing the lower extremities as percussion instruments. In a previous study these authors reported decreased injury prevalence among tap dancers compared to other dance and sports participants. No biomechanical analyses of tap dance exist to explain this finding. The purpose of the current pilot study was to provide a preliminary overview of normative peak kinetic and kinematic data, based on the hypothesis that tap dance generates relatively low ground reaction forces and joint forces and moments. Six professional tap dancers performed four common tap dance sequences that produced data captured by the use of a force platform and a five-camera motion analysis system. The mean vertical ground reaction force for all sequences was found to be 2.06+/-0.55 BW. Mean peak sagittal, frontal, and transverse plane joint moments (hip, knee, and ankle) ranged from 0.07 to 2.62 N.m/kg. These small ground reaction forces and joint forces and moments support our hypothesis, and may explain the relatively low injury incidence in tap dancers. Nevertheless, the analysis is highly complex, and other factors remain to be studied and clarified.

• Perceiving dance: schematic expectations guide experts' scanning of a contemporary dance film.

  Authors: Catherine Stevens, Heather Winskel, Clare Howell, Lyne-Marine Vidal, Cyril Latimer, Josephine Milne-Home

  Journal of dance medicine & science : official publication of the International Association for Dance Medicine & Science. 14(1):19-25.

  Eye fixations and saccades (eye movements) of expert and novice dance observers were compared to determine the effect of acquired expectations on observations of human movement, body morphology, andEye fixations and saccades (eye movements) of expert and novice dance observers were compared to determine the effect of acquired expectations on observations of human movement, body morphology, and dance configurations. As hypothesized, measured fixation times of dance experts were significantly shorter than those of novices. In a second viewing of the same sequences, novices recorded significantly shorter fixations than those recorded during viewing session 1. Saccades recorded from experts were significantly faster than those of novices. Although both experts and novices fixated background regions, most likely making use of extrafoveal or peripheral vision to anticipate movement and configurations, novices fixated background regions significantly more than experts in viewing session 1. Their enhanced speed of visual processing suggests that dance experts are adept at anticipating movement and rapidly processing material, probably aided by acquired schemata or expectations in long-term memory and recognition of body and movement configurations.

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