Prevalence of low bone mineral density in female dancers

Patellofemoral pain and musculoskeletal features in young pre- and post-pubertal female dancers

The aim of this study was to examine associations between patellofemoral pain (PFP) and musculoskeletal features (such as tendon structure and bone properties) in young (pre- and post-pubertal) female dancers. A total of 49 dancers participated in this study (mean age 13.6 ± 2.9; weight 47.0 ± 13.2; height 153.7 ± 12.9 and body mass index (BMI) 19.4 ± 3.1) and were assessed for the following factors: dance background and Tanner stage through interviews; ultrasonography assessments of bone properties and patellar tendon structure through ultrasonographic tissue characterization and quantitative ultrasound, respectively; and anthropometric measurements, muscle strength, range of motion (ROM), hypermobility and PFP through physical examinations. PFP was found in 49% of the participants. Post-pubertal dancers with no-PFP were found to have greater muscle strength, greater radial and tibial properties, and better tendon structure compared to pre-pubertal dancers with PFP and compared to pre-pubertal dancers with no-PFP [F(2, 41) = 18.64, p < .001; F(2, 41) = 20.46, p < .001; F(2, 41) = 33.06, p < .001; and, F(2, 41) = 6.02, p = .007, respectively]. Logistic regression showed that tibial bone properties and range of movement (ROM) in hip external rotation were significantly associated with PFP [odds ratio (OR) = .889 and OR = 2.653, respectively; Cox & Snell R2 = .701]. The study revealed a high prevalence of PFP among young dancers, with low bone properties and hyperjoint ROM emerging as the main factors that are related to PFP. These findings should be addressed by medical teams, athletic trainers, and dance teachers regarding the need for implementing modifications to dance training programmes and injury-prevention strategies in young pre-pubertal dancers.

Differences in bone mineral density and associated factors in dancers and other female athletes

Dancers are susceptible to relative energy deficiency in sport (RED-S), specifically low bone mineral density (BMD). Little is known about how dancers' BMD compares to other athletic populations. The objective of this study was to examine the association between participant characteristics and total body areal BMD (aBMD) among female pre-professional dancers compared to other female athletes. Two hundred sixty-nine females (132 pre-professional dancers (17.6 (3.2) years) and 137 sport participants (22.8 (2.6) years) were included in this study. aBMD (g/cm2) was estimated using dual X-ray absorptiometry. Multivariable linear regression was used to examine the association between height-adjusted z-scores of total body aBMD (aBMD-Z) and age (years), body mass index (BMI) (z-score), supplement intake, history of stress fracture, irregular menses, MRI/bone scan, 1-year injury history, oral contraceptives, and activity (dance/sport). Total body aBMD and aBMD-Z were lower in dancers than athletes (dancers: aBMD = 1.03 g/cm2 (95% CI: 1.01, 1.05); aBMD-Z = -0.28 (-0.43, -0.12) (p < 0.001); athletes: aBMD = 1.14 g/cm2 (95% CI: 1.12, 1.16); aBMD-Z = 0.41 (0.25, 0.57) (p < 0.001)). aBMD-Z increased with age (β = 0.054, 95% CI: 0.017, 0.092; p = 0.004) and BMI (β = 0.221, 95% CI: 0.006, 0.415; p = 0.043). Activity type modified the relationship between BMI and aBMD-Z (β = 0.323, 95% CI: 0.025, 0.621; p < 0.033) with a stronger positive association in dancers, compared to other female athletes. Dancers had lower total body aBMD and aBMD-Z than other female athletes. aBMD-Z increases with age in female pre-professional dancers and other female athletes. A stronger association exists between aBMD-Z and BMI in dancers than athletes. Future studies should consider changes in aBMD-Z during adolescence and associations with increased risk of bone injury.

Effects of the Type of Exercise Training on Bone Health Parameters in Adolescent Girls: A Systematic Review

Interventional studies offer strong evidence for exercise's osteogenic impact on bone particularly during growth. With rising osteoporosis rates in older women, enhancing bone strength early in life is crucial. Thus, investigating the osteogenic effects of different types of physical activities in young females is crucial. Despite varied findings, only two systematic reviews tried to explore this topic without examining how different types of exercise may affect bone health in adolescent girls. The first aim of this systematic review was to assess the impact of exercise training on bone health parameters in adolescent girls, and the second aim was to investigate whether the type of exercise training can modulate this effect. A systematic literature search was conducted using common electronic databases from inception - January 2023. Seven studies (355 participants) were eligible for inclusion in this systematic review. Two studies dealt with resistance training, 3 studies applied plyometric training, 1 study used team sports, and 1 study used dancing. Results indicate that plyometric training increases lumbar spine bone mass in adolescent girls. Well-designed randomized controlled trials with a proper training period (> 12 weeks) are needed to advocate a specific type of training which has the highest osteogenic effect.

Examination of the Cumulative Risk Assessment and Nutritional Profiles among College Ballet Dancers

This study examined female collegiate ballet dancers' (n = 28) Female Athlete Triad (Triad) risk via the Cumulative Risk Assessment (CRA) and nutritional profiles (macro- and micronutrients; n = 26). The CRA identified Triad return to play criteria (RTP: Full Clearance, Provisional Clearance, or Restricted/Medical Disqualified) by assessing eating disorder risk, low energy availability, menstrual cycle dysfunction, and low bone mineral density. Seven-day dietary assessments identified any energy imbalances of macro- and micronutrients. Ballet dancers were identified as low, within normal, or high for each of the 19 nutrients assessed. Basic descriptive statistics assessed CRA risk classification and dietary macro- and micronutrient levels. Dancers averaged 3.5 ± 1.6 total score on the CRA. Based on these scores, the RTP outcomes revealed Full Clearance 7.1%, n = 2; Provisional Clearance 82.1%, n = 23; and Restricted/Medical Disqualification 10.7%, n = 3. Dietary reports revealed that 96.2% (n = 25) of ballet dancers were low in carbohydrates, 92.3% (n = 24) low in protein, 19.2% (n = 5) low in fat percent, 19.2% (n = 5) exceeding saturated fats, 100% (n = 26) low in Vitamin D, and 96.2% (n = 25) low in calcium. Due to the variability in individual risks and nutrient requirements, a patient-centered approach is a critical part of early prevention, evaluation, intervention, and healthcare for the Triad and nutritional-based clinical evaluations.

Pharmacological and Non-Pharmacological Agents versus Bovine Colostrum Supplementation for the Management of Bone Health Using an Osteoporosis-Induced Rat Model

Osteoporosis is defined by loss of bone mass and deteriorated bone microarchitecture. The present study compared the effects of available pharmacological and non-pharmacological agents for osteoporosis [alendronate (ALE) and concomitant supplementation of vitamin D (VD) and calcium (Ca)] with the effects of bovine colostrum (BC) supplementation in ovariectomized (OVX) and orchidectomized (ORX) rats. Seven-month-old rats were randomly allocated to: (1) placebo-control, (2) ALE group (7.5 μg/kg of body weight/day/5 times per week), (3) VD/Ca group (VD: 35 μg/kg of body weight/day/5 times per week; Ca: 13 mg/kg of body weight/day/3 times per week), and (4) BC supplementation (OVX: 1.5 g/day/5 times per week; ORX: 2 g/day/5 times per week). Following four months of supplementation, bone microarchitecture, strength and bone markers were evaluated. ALE group demonstrated significantly higher Ct.OV, Ct.BMC, Tb.Th, Tb.OV and Tb.BMC and significantly lower Ct.Pr, Tb.Pr, Tb.Sp, Ct.BMD and Tb.BMD, compared to placebo (p < 0.05). BC presented significantly higher Ct.Pr, Ct.BMD, Tb.Pr, Tb.Sp, and Tb.BMD and significantly lower Ct.OV, Ct.BMC, Tb.Th, Tb.OV and Tb.BMC compared to ALE in OVX rats (p < 0.05). OVX rats receiving BC experienced a significant increase in serum ALP and OC levels post-supplementation (p < 0.05). BC supplementation may induce positive effects on bone metabolism by stimulating bone formation, but appear not to be as effective as ALE.

The Limited Impact of Low-Volume Recreational Dance on Three-Compartment Body Composition and Apparent Bone Mineral Density in Young Girls

Recreational dance is practiced worldwide as a multidimensional physical activity with a potential for prevention of a sedentary lifestyle and overweight/obesity. This study explored in young (7−15 year; n = 21) girls the effect of long-term (>1 year) exposure to recreational (2 h/w) dancing on three-compartment body composition. Recreational dancers (RD) were compared with recreational (≤4 h/w) artistic gymnasts (RG, n = 22) and physically active young girls not involved in structured extracurricular physical activity (control; C, n = 22), adjusting for confounding variables (age, body mass, menarche). We hypothesized for RD an intermediate body composition between RG and C. The three groups had similar age and body mass index. Body composition indices in RD were intermediate between that of C and RG, but RD values were not statistically significantly different vs. C. This agreed with the not statistically significant higher energy expenditure (MET-min/w) in RD vs. C (1357.7 ± 805.32 and 1090.9 ± 596.63, p = 0.172). In conclusion, long-term recreational dance exposure at low volume had limited positive effect on body composition of young girls vs. unstructured extracurricular physical activity. Future work will explore the potential of recreational dance at higher volume (3−4 h/w) to improve body composition in young girls.

Associations between nutrition, energy expenditure and energy availability with bone mass acquisition in dance students: a 3-year longitudinal study

Three years of study showed that female and male vocational dancers displayed lower bone mass compared to controls, at forearm, lumbar spine and femoral neck. Energy intake was found to positively predict bone mass accruals only in female dancers at femoral neck. Vocational dancers can be a risk population to develop osteoporosis.

PURPOSE

To determine whether risk factors normally associated with low bone mass in athletic populations (i.e. nutrition intake, energy expenditure and energy availability) are significant predictors of bone mass changes in vocational dance students.

METHODS

The total of 101 vocational dancers (63 females, 12.8 ± 2.2 years; 38 males, 12.7 ± 2.2 years) and 115 age-matched controls (68 females, 13.0 ± 2.1 years; 47 males, 13.0 ± 1.8 years) were monitored for 3 consecutive years. Bone mass parameters were measured annually at impact sites (femoral neck, FN; lumber spine, LS) and non-impact site (forearm) using DXA. Nutrition (3-day record), energy expenditure (accelerometer), energy availability and IGF-1 serum concentration (immunoradiometric assays) were also assessed.

RESULTS

Female and male vocational dancers had consistently reduced bone mass at all anatomical sites (p < 0.001) than controls. IGF-1 did not differ between male vocational dancers and controls, but female dancers showed it higher than controls. At baseline, calcium intake was significantly greater in female vocational dancers than controls (p < 0.05). Male vocational dancers' fat and carbohydrate intakes were significantly lower than matched controls (p < 0.001 and p < 0.05, respectively). Energy availability of both female and male vocational dancers was within the normal range. A significant group effect was found at the FN regarding energy intake (p < 0.05) in female dancers. No significant predictors were found to explain bone mass differences in males.

CONCLUSION

Our 3-year study revealed that both female and male vocational dancers displayed lower bone mass compared to controls, at both impact and non-impact sites. The aetiology of these findings may be grounded on factors different than those usually considered in athletic populations.

A Neuroprotective Bovine Colostrum Attenuates Apoptosis in Dexamethasone-Treated MC3T3-E1 Osteoblastic Cells

Glucocorticoid-induced osteoporosis (GIO) is one of the most common secondary forms of osteoporosis. GIO is partially due to the apoptosis of osteoblasts and osteocytes. In addition, high doses of dexamethasone (DEX), a synthetic glucocorticoid receptor agonist, induces neurodegeneration by initiating inflammatory processes leading to neural apoptosis. Here, a neuroprotective bovine colostrum against glucocorticoid-induced neuronal damage was investigated for its anti-apoptotic activity in glucocorticoid-treated MC3T3-E1 osteoblastic cells. A model of apoptotic osteoblastic cells was developed by exposing MC3T3-E1 cells to DEX (0-700 μM). Colostrum co-treated with DEX was executed at 0.1-5.0 mg/mL. Cell viability was measured for all treatment schedules. Caspase-3 activation was assessed to determine both osteoblast apoptosis under DEX exposure and its potential prevention by colostrum co-treatment. Glutathione reduced (GSH) was measured to determine whether DEX-mediated oxidative stress-driven apoptosis is alleviated by colostrum co-treatment. Western blot was performed to determine the levels of p-ERK1/2, Bcl-XL, Bax, and Hsp70 proteins upon DEX or DEX plus colostrum exposure. Colostrum prevented the decrease in cell viability and the increase in caspase-3 activation and oxidative stress caused by DEX exposure. Cells, upon colostrum co-treated with DEX, exhibited higher levels of p-ERK1/2 and lower levels of Bcl-XL, Bax, and Hsp70. Our data support the notion that colostrum may be able to reduce DEX-induced apoptosis possibly via the activation of the ERK pathway and modulation of the Hsp70 system. We provided preliminary evidence on how bovine colostrum, as a complex and multi-component dairy product, in addition to its neuroprotective action, may affect osteoblastic cell survival undergoing apoptosis.

Bovine Colostrum Supplementation Improves Bone Metabolism in an Osteoporosis-Induced Animal Model

Osteoporosis is characterized by bone loss. The present study aims to investigate the effects of bovine colostrum (BC) on bone metabolism using ovariectomized (OVX) and orchidectomized (ORX) rat models. Twenty-seven-week-old Wistar Han rats were randomly assigned as: (1) placebo control, (2) BC supplementation dose 1 (BC1: 0.5 g/day/OVX, 1 g/day/ORX), (3) BC supplementation dose 2 (BC2: 1 g/day/OVX, 1.5 g/day/ORX) and (4) BC supplementation dose 3 (BC3: 1.5 g/day/OVX, 2 g/day/ORX). Bone microarchitecture, strength, gene expression of VEGFA, FGF2, RANKL, RANK and OPG, and bone resorption/formation markers were assessed after four months of BC supplementation. Compared to the placebo, OVX rats in the BC1 group exhibited significantly higher cortical bone mineral content and trabecular bone mineral content (p < 0.01), while OVX rats in the BC3 group showed significantly higher trabecular bone mineral content (p < 0.05). ORX rats receiving BC dose 2 demonstrated significantly higher levels of trabecular bone mineral content (p < 0.05). Serum osteocalcin in the ORX was pointedly higher in all BC supplementation groups than the placebo (BC1: p < 0.05; BC2, BC3: p < 0.001). Higher doses of BC induced significantly higher relative mRNA expression of OPG, VEGFA, FGF2 and RANKL (p < 0.05). BC supplementation improves bone metabolism of OVX and ORX rats, which might be associated with the activation of the VEGFA, FGF2 and RANKL/RANK/OPG pathways.

Evaluation of two different 1-year training programs among prepuberal female children

The aim of this study was to analyse and compare the effects of two different dance training concepts in terms of anthropometric indices and supervised motor test performance between two groups of 56 prepuberal girls. The first group, composed of 29 girls, performed a typical classical dance training program (D group), while the second one, composed of 27 girls, followed a mixed training (D&R group) workout, with classical dance exercises alternated to rhythmic gymnastics. Anthropometric and exercise performance data were collected and assessed initially (T1) and after a 1-year (T2) training program. Data collected were firstly tested for collinearity using Belsley’s test and, after their normality was tested through the Shapiro–Wilk test, analysis of variance (ANOVA) tests were performed on a subset of noncollinear variables. The two groups showed improvements in both anthropometric parameters and exercise performance; however, no differences arose between the variation of anthropometric parameters between the two groups. On the other hand, exercise performance was improved in some fields of the D&R group, particularly in exercises regarding the upper body, such as pull-ups, chin-ups and sit-ups. In conclusion, our data provide evidence that a specific training program consisting of classic dance plus rhythmic gymnastics exercises (D&R) has a greater impact compared to a program of simple classic dance, in terms of skill performance without impairment of anthropometric parameters.

A Practice-Inspired Mindset for Researching the Psychophysiological and Medical Health Effects of Recreational Dance (Dance Sport)

“Dance” has been associated with many psychophysiological and medical health effects. However, varying definitions of what constitute “dance” have led to a rather heterogenous body of evidence about such potential effects, leaving the picture piecemeal at best. It remains unclear what exact parameters may be driving positive effects. We believe that this heterogeneity of evidence is partly due to a lack of a clear definition of dance for such empirical purposes. A differentiation is needed between (a) the effects on the individual when the activity of “dancing” is enjoyed as a dancer within different dance domains (e.g., professional/”high-art” type of dance, erotic dance, religious dance, club dancing, Dance Movement Therapy (DMT), and what is commonly known as hobby, recreational or social dance), and (b) the effects on the individual within these different domains, as a dancer of the different dance styles (solo dance, partnering dance, group dance; and all the different styles within these). Another separate category of dance engagement is, not as a dancer, but as a spectator of all of the above. “Watching dance” as part of an audience has its own set of psychophysiological and neurocognitive effects on the individual, and depends on the context where dance is witnessed. With the help of dance professionals, we first outline some different dance domains and dance styles, and outline aspects that differentiate them, and that may, therefore, cause differential empirical findings when compared regardless (e.g., amount of interpersonal contact, physical exertion, context, cognitive demand, type of movements, complexity of technique and ratio of choreography/improvisation). Then, we outline commonalities between all dance styles. We identify six basic components that are part of any dance practice, as part of a continuum, and review and discuss available research for each of them concerning the possible health and wellbeing effects of each of these components, and how they may relate to the psychophysiological and health effects that are reported for “dancing”: (1) rhythm and music, (2) sociality, (3) technique and fitness, (4) connection and connectedness (self-intimation), (5) flow and mindfulness, (6) aesthetic emotions and imagination. Future research efforts might take into account the important differences between types of dance activities, as well as the six components, for a more targeted assessment of how “dancing” affects the human body.

Bone mineral density and low bone mass in severely burned patients: A retrospective cohort study

INTRODUCTION

Severe burns can alter bone metabolism through different mechanisms. Despite prior published studies describing the association between burns and a decrease in bone mineral density (BMD), no clinical guidelines currently exist recommending the systematic evaluation of bone health in patients after severe burns. This study aims to describe the BMD of individuals with severe burn injuries and healthy controls and determine the frequency of low-to-normal bone mass (LNBM) and BMD below the expected range for age (BEA).

MATERIALS AND METHODS

We conducted a retrospective cohort of patients with either severe thermal or electrical burns and healthy controls paired by gender and age. We performed a dual-energy X-ray absorptiometry at least 90 days after the burn and collected data from each patient's clinical evaluation and clinical file.

RESULTS

A total of 77 patients (64 men and 13 women) and their paired controls were included in the study (age [mean ± standard deviation, SD]: 30.37 ± 8.66 years). Patients participated in the study an average of 315 ± 438 days after their burn. The BMD (grs/cm2) in total hip burned vs controls was: 0.998 ± 0.135 vs 1.059 ± 0.12 (p = 0.004); femoral neck 0.876 ± 0.121 vs 0.915 ± 0.097 (p = 0.031), spine 0.977 ± 0.127 vs 1.003 ± 0.076 (p = 0.132).The Z-scores for total hip were - 0.06 ± 1.05 vs 0.41 ± 0.80 (p = 0.002); for neck -0.39 ± 0.89 vs -0.01 ± 0.77 (p = 0.005); and for spine -0.75 ± 1.11 vs -0.32 ± 0.73 (p = 0.005). The proportion of subjects with BMD BEA in burns vs controls was 5.2 vs 1.2% (p = 0.05) in total hip, 3.9 vs 0% (p = 0.045) in the neck, and 18.2 vs 1.2% (p = 0.001) in the spine. The logistic regression model found-in burn patients vs controls-an OR of 9.83 for BMD BEA (CI 95%: 2.17-44.45, p = 003), OR = 4.05 for electrical burns (CI 95%: 1.72-20.89, p = 004) and OR = 15.16 for thermal burns (CI 95%: 2.91-79.00, p = 001). The model also found an OR = 2.48 for LNBM (CI 95%: 1.25-4.93, p = 0.009). The burn variables associated with BMD BEA at any site in the patients were BMI >25 Kg/m2 with an OR = 0.180 (CI 95%: 0.046-0.710, p = 0.014); and the lower limb amputation with an OR = 7.33 (CI 95%; 1.12-48.33, p = 0.038). Five burn patients had a fragility fracture.

CONCLUSION

BMD was significantly lower in severely burned patients than in controls, and the proportion BMD BEA cases was significantly higher in the burn patient sample. Severe burns are a strong independent predictor of bone loss, and this risk is maintained for an extended period after the burn.

Special Considerations for Growing Dancers

Care of young dancers requires a unique approach during a critical time of growth and development. Young dancers' well-being depends on factors including sleep, mental health, growth-associated musculoskeletal imbalances, and nutrition. Puberty is a particularly important time for young dancers. It coincides with an increased commitment to their art form and physical/psychosocial changes. It is imperative for practitioners to understand these various factors in order to optimize young dancers' health and allow them to safely train and perform.

Access to Health Care Among Dancers

Dancers require a unique blend of artistry and athleticism, and have specific medical problems that require the expertise of health care professionals who understand the demands of the performing arts. There is often a lack of alignment between health care systems and dancers' perceptions of care. Factors including country of residence, socioeconomic status, and local infrastructure can affect dancers' access to health care. Efforts to improve access are evident, and specialized care for dancers has grown significantly in recent decades. By developing and refining systems of care delivery, there are opportunities to ensure optimal health of the dancer population.

Bone mineral density in adolescent elite ballet dancers

BACKGROUND

Data documenting BMD in pre-professional adolescent ballet dancers is limited. This cross-sectional study assesses bone mineral density (BMD) in young adolescent elite ballet dancers and compares BMD values between males and females (with and without normal menarche) and body composition between dancers with and without low Z-score.

METHODS

Cross-sectional study of third year ballet students (female=23; male=15; mean age 14.7 years; SD: 0.5) of The Royal Ballet School of Antwerp (Belgium) training 22 hours a week. They completed questionnaires and underwent dual energy X-ray absorptiometry (DXA) to measure BMD and body composition. Each female participant completed questionnaires assessing menstrual status.

RESULTS

DXA revealed that 12 out of 38 (32%) of the dancers had Z-score <-1. On average, male dancers had a lower BMD compared to an age-matched reference population (mean Z-score -0.9; SD 0.5), with 7 out of 15 having Z-score <-1. Overall, absolute BMD values were highest in the legs, followed by spine and arms. Dancers with Z-score <-1 had a significantly lower total mass. 43% of female ballet dancers had not yet had their first period and 39% had oligomenorrhea, but no significant differences between groups was detected.

CONCLUSIONS

A third of adolescent elite ballet dancers had low to very low Z-score. Nearly 2 out of 3 dancers with a Z-score <-1 were males, showing that low BMD is not limited to female dancers. Among female dancers menstrual dysfunction was frequent, without apparent impact on BMD or body composition in the studied age group.

Endocrine parameters in association with bone mineral accrual in young female vocational ballet dancers

Less is known on bone mass gains in dancers involved in vocational dance training. The present study found that, as young vocational dancers progress on their professional training, their bone health remains consistently lower compared to non-exercising controls. Endocrine mechanisms do not seem to explain these findings.

PURPOSE

Little is known on bone mass development in dancers involved in vocational training. The aim of the present study was to model bone mineral content (BMC) accruals and to determine whether circulating levels of oestrogens, growth hormone (GH), and insulin-like growth factor I (IGF-1) explain differences in bone mass gains between vocational dance students and matched controls.

METHODS

The total of 67 vocational female dancers (VFDs) and 68 aged-matched controls (12.1 ± 1.9 years and 12.7 ± 2.0 years at baseline, respectively) were followed for two consecutive years (34 VFD and 31 controls remained in the study for the full duration). BMC was evaluated annually at impact [femoral neck (FN); lumbar spine (LS)] and non-impact sites (forearm) using DXA. Anthropometry, age at menarche (questionnaire), and hormone serum concentrations (immunoradiometric assays) were also assessed for the same period.

RESULTS

VFD demonstrated consistently reduced body weight (p < 0.001) and BMC at all three anatomical sites (p < 0.001) compared to controls throughout the study period. Menarche, body weight, GH, and IGF-1 were significantly associated with bone mass changes over time (p < 0.05) but did not explain group differences in BMC gains at impact sites (p > 0.05). However, body weight did explain the differences between groups in terms of BMC gains at the forearm (non-impact site).

CONCLUSION

Two consecutive years of vocational dance training revealed that young female dancers demonstrate consistently lower bone mass compared to controls at both impact and non-impact sites. The studied endocrine parameters do not seem to explain group differences in terms of bone mass gains at impact sites.

Assessment of Dietary Intake, Energy Status, and Factors Associated With RED-S in Vocational Female Ballet Students

Elite ballet dancers are at risk of health issues associated with Relative Energy Deficiency in Sport (RED-S). This study determined the nutritional status, estimated energy status, and assessed factors related to RED-S in vocational female ballet students. Using a cross-sectional study design, we measured dietary intake (food diaries and 24 h dietary-recall) and energy expenditure (accelerometry) in vocational female ballet students (n = 20; age: 18.1 ± 1.1 years; body mass index: 19.0 ± 1.6 kg·m²; body fat: 22.8 ± 3.4%) over 7 days, including 5 weekdays (with dance training) and 2 weekend days (without scheduled dance training). Furthermore, we assessed eating behaviors, menstrual function, risk of RED-S (questionnaires), and body composition (dual x-ray absorptiometry). Energy and macronutrient intakes of vocational ballet students were similar during weekdays and weekend days (P > 0.050), whereas total energy expenditure was greater on weekdays than weekend days (P < 0.010; 95% CI: 212, 379). Energy balance was lower on weekdays (-425 ± 465 kcal·day^-1) than weekend days (-6 ± 506 kcal·day^-1, P = 0.015; 95% CI: -748, -92). Exercise energy expenditure was greater on weekdays (393 ± 103 kcal·day^-1) than weekend days (213 ± 129 kcal·day^-1; P < 0.010; 95% CI: 114, 246), but energy availability was similar between time periods (weekdays 38 ± 13 kcal·kg FFM·day^-1; weekend days 44 ± 13 kcal·kg FFM·day^-1; P = 0.110). Overall, 35% of participants had an energy intake <1,800 kcal·day^-1, 44% had reduced energy availability (30-45 kcal·kg FFM·day^-1), and 22% had low energy availability (<30 kcal·kg FFM·day^-1). Menstrual dysfunctions were reported in 40% of participants; 15 and 25% reported oligomenorrhea and secondary amenorrhea, respectively; while 65% were classified at risk of RED-S (based on the Low Energy Availability in Females Questionnaire). All participants had adequate bone health (bone mineral density Z-score: 1.1 ± 0.9 SD), but 20% had <85% expected body weight. The observation of an energy deficit in vocational female ballet students was primarily attributed to an inability to plan energy intake and thereby meet higher energy requirements during ballet training weekdays. Screening for factors associated with RED-S and tailoring education programs to inform energy and nutrition requirements for health and training are recommended in elite young ballet students.

Genetic variation in Wnt/β-catenin and ER signalling pathways in female and male elite dancers and its associations with low bone mineral density: a cross-section and longitudinal study

The association of genetic polymorphisms with low bone mineral density in elite athletes have not been considered previously. The present study found that bone mass phenotypes in elite and pre-elite dancers are related to genetic variants at the Wnt/β-catenin and ER pathways.

INTRODUCTION

Some athletes (e.g. gymnasts, dancers, swimmers) are at increased risk for low bone mineral density (BMD) which, if untreated, can lead to osteoporosis. To investigate the association of genetic polymorphisms in the oestrogen receptor (ER) and the Wnt/β-catenin signalling pathways with low BMD in elite and pre-elite dancers (impact sport athletes).

METHODS

The study included three phases: (1) 151 elite and pre-elite dancers were screened for the presence of low BMD and traditional osteoporosis risk factors (low body weight, menstrual disturbances, low energy availability); (2) a genetic association study was conducted in 151 elite and pre-elite dancers and age- and sex- controls; (3) serum sclerostin was measured in 101 pre-elite dancers and age- and sex-matched controls within a 3-year period.

RESULTS

Eighty dancers revealed low BMD: 56.3% had at least one traditional osteoporosis risk factor, whereas 28.6% did not display any risk factor (37.2% revealed traditional osteoporosis risk factors, but had normal BMD). Body weight, menstrual disturbances and energy availability did not fully predict bone mass acquisition. Instead, genetic polymorphisms in the ER and Wnt/β-catenin pathways were found to be risk factors for low BMD in elite dancers. Sclerostin was significantly increased in dancers compared to controls during the 3-year follow-up (p < 0.05).

CONCLUSIONS

Elite and pre-elite dancers demonstrate high prevalence of low BMD, which is likely related to genetic variants at the Wnt/β-catenin and ER pathways and not to factors usually associated with BMD in athletes (body weight, menstrual disturbances, energy deficiency).

Low RMRratio as a Surrogate Marker for Energy Deficiency, the Choice of Predictive Equation Vital for Correctly Identifying Male and Female Ballet Dancers at Risk

Ballet dancers are reported to have an increased risk for energy deficiency with or without disordered eating behavior. A low ratio between measured (m) and predicted (p) resting metabolic rate (RMRratio < 0.90) is a recognized surrogate marker for energy deficiency. We aimed to evaluate the prevalence of suppressed RMR using different methods to calculate pRMR and to explore associations with additional markers of energy deficiency. Female (n = 20) and male (n = 20) professional ballet dancers, 19–35 years of age, were enrolled. mRMR was assessed by respiratory calorimetry (ventilated open hood). pRMR was determined using the Cunningham and Harris–Benedict equations, and different tissue compartments derived from whole-body dual-energy X-ray absorptiometry assessment. The protocol further included assessment of body composition and bone mineral density, blood pressure, disordered eating (Eating Disorder Inventory-3), and for females, the Low Energy Availability in Females Questionnaire. The prevalence of suppressed RMR was generally high but also clearly dependent on the method used to calculate pRMR, ranging from 25% to 80% in males and 35% to 100% in females. Five percent had low bone mineral density, whereas 10% had disordered eating and 25% had hypotension. Forty percent of females had elevated Low Energy Availability in Females Questionnaire score and 50% were underweight. Suppressed RMR was associated with elevated Low Energy Availability in Females Questionnaire score in females and with higher training volume in males. In conclusion, professional ballet dancers are at risk for energy deficiency. The number of identified dancers at risk varies greatly depending on the method used to predict RMR when using RMRratio as a marker for energy deficiency.

Lower Leg Morphology and Stretch-Shortening Cycle Performance of Dancers

Greater levels of bone ultimate fracture load, bone stress–strain index, muscle cross-sectional area, and maximal voluntary isometric plantarflexion (MVIP) strength of the lower leg may be adaptations from chronic exposure to stretch-shortening cycle (SSC) actions. Dancers, a population that habitually performs SSC movements primarily about the ankle joint, may serve as a novel population to gain broader understanding of SSC function. A total of 10 female collegiate dancers and 10 untrained controls underwent peripheral quantitative computed tomography scans of both lower legs and performed MVIPs, countermovement hops, and drop hops at 20, 30, and 40 cm on a custom-made inclined sled. Dancers had greater right and left ultimate fracture load values and significantly (P ≤ .05) greater left leg stress–strain index than controls. Dancers had significantly larger right and left muscle cross-sectional area and MVIP values and hopped significantly higher during all hopping conditions in comparison with controls. Average force–time and power–time curves revealed significantly greater relative force and power measurements during the concentric phase for all hopping conditions in dancers when compared with controls. This investigation provides evidence that dance may be a stimulus for positive muscle and bone adaptations, strength levels, and enhanced SSC capabilities.

Bone mineral density in pre-professional female ballet dancers: A systematic review and meta-analysis

OBJECTIVES

To quantitatively compare bone mineral density (BMD) outcomes between pre-professional female adolescent ballet dancers and control populations.

DESIGN

Systematic review and meta-analysis.

METHODS

Six electronic databases and relevant journals were systematically searched up to August 2017. Included articles examined BMD in adolescent females undergoing pre-professional ballet training and healthy age-matched controls with an available English full text. Dancers were aged 15-19 years and trained in ballet at least 10h per week. BMD data were analysed via standardized mean difference to account for differences in reporting methods RESULTS: From 3984 potential articles, 8 cross-sectional studies were accepted for inclusion, which compared 293 dancers (16.9±0.8 years) to 333 controls (16.9±0.9 years). No data were available from longitudinal studies. Dancers displayed lower BMD at the radius and higher BMD at the femoral neck, femoral trochanter and Ward's triangle. No significant differences were observed in the lumbar spine or tibia. The overall study quality was low and heterogeneity was present in some analyses.

CONCLUSIONS

This meta-analysis indicates that there may be a site-specific osteogenic effect of pre-professional classical ballet training in adolescent females, with a notable and concerning finding of reduced upper limb BMD compared to age-matched controls. Longitudinal cohort studies are required to confirm the effects of pre-professional ballet training on BMD during adolescence.

Bone mineral density in vocational and professional ballet dancers

According to existing literature, bone health in ballet dancers is controversial. We have verified that, compared to controls, young female and male vocational ballet dancers have lower bone mineral density (BMD) at both impact and non-impact sites, whereas female professional ballet dancers have lower BMD only at non-impact sites.

INTRODUCTION

The aims of this study were to (a) assess bone mineral density (BMD) in vocational (VBD) and professional (PBD) ballet dancers and (b) investigate its association with body mass (BM), fat mass (FM), lean mass (LM), maturation and menarche.

METHODS

The total of 152 VBD (13 ± 2.3 years; 112 girls, 40 boys) and 96 controls (14 ± 2.1 years; 56 girls, 40 boys) and 184 PBD (28 ± 8.5 years; 129 females, 55 males) and 160 controls (27 ± 9.5 years; 110 female, 50 males) were assessed at the lumbar spine (LS), femoral neck (FN), forearm and total body by dual-energy X-ray absorptiometry. Maturation and menarche were assessed via questionnaires.

RESULTS

VBD revealed lower unadjusted BMD at all anatomical sites compared to controls (p < 0.001); following adjustments for Tanner stage and gynaecological age, female VBD showed similar BMD values at impact sites. However, no factors were found to explain the lower adjusted BMD values in VBD (female and male) at the forearm (non-impact site), nor for the lower adjusted BMD values in male VBD at the FN. Compared to controls, female PBD showed higher unadjusted and adjusted BMD for potential associated factors at the FN (impact site) (p < 0.001) and lower adjusted at the forearm (p < 0.001). Male PBD did not reveal lower BMD than controls at any site.

CONCLUSIONS

Both females and males VBD have lower BMD at impact and non-impact sites compared to control, whereas this is only the case at non-impact site in female PBD. Maturation seems to explain the lower BMD at impact sites in female VBD.

Bone mass of female dance students prior to professional dance training: A cross-sectional study

Background

Professional dancers are at risk of developing low bone mineral density (BMD). However, whether low BMD phenotypes already exist in pre-vocational dance students is relatively unknown.

Aim

To cross-sectionally assess bone mass parameters in female dance students selected for professional dance training (first year vocational dance students) in relation to aged- and sex-matched controls.

Methods

34 female selected for professional dance training (10.9yrs ±0.7) and 30 controls (11.1yrs ±0.5) were examined. Anthropometry, pubertal development (Tanner) and dietary data (3-day food diary) were recorded. BMD and bone mineral content (BMC) at forearm, femur neck (FN) and lumbar spine (LS) were assessed using Dual-Energy X-Ray Absorptiometry. Volumetric densities were estimated by calculating bone mineral apparent density (BMAD).

Results

Dancers were mainly at Tanner pubertal stage I (vs. stage IV in controls, p<0.001), and demonstrated significantly lower body weight (p<0.001) and height (p<0.01) than controls. Calorie intake was not different between groups, but calcium intake was significantly greater in dancers (p<0.05). Dancers revealed a significantly lower BMC and BMD values at all anatomical sites (p<0.001), and significantly lower BMAD values at the LS and FN (p<0.001). When adjusted for covariates (body weight, height, pubertal development and calcium intake), dance students continued to display a significantly lower BMD and BMAD at the FN (p<0.05; p<0.001) at the forearm (p<0.01).

Conclusion

Before undergoing professional dance training, first year vocational dance students demonstrated inferior bone mass compared to controls. Longitudinal models are required to assess how bone health-status changes with time throughout professional training.

Physical exercise associated with improved BMD independently of sex and vitamin D levels in young adults

Purpose

Young men and women accrue the majority of their bone mass in their teens and twenties, where their bone mass peaks (PBM), yet little is known about the roles of physical exercise, vitamin D levels and bone mineral density (BMD) near PBM.

Methods

To comparatively examine the effect of physical exercise and two vitamin D levels (insufficient s-25[OH]D <50 nmol/L and sufficient s-25[OH]D >80 nmol/L) on the BMD measured at the femoral neck, total hip (bilaterally) and the lumbar spine (L2–L4) in male and female participants approaching PBM.

Results

The insufficient s-25[OH]D group, median age 21.6 (19.8–22.8) years, and BMI 24.2 ± 5.0 kg/m² had BMD 0.10 (0.03, 0.17) g/cm² (p = 0.008) lower at all DXA-scan sites compared to the sufficient s-25[OH]D group, median age 19.5 (19.0–22.3) years, and BMI of 22.6 ± 1.8 kg/m². Exercise was positively associated with the BMD at all DXA-scan sites (p_trend = 0.0001) and with equal benefit; there was no interaction between exercise and the DXA-scan site (p = 0.09). The male participants did not have a systematically higher BMD than the female participants for all scan sites; only for hips total and femoral neck bilaterally, while it was equal at the lumbar spine.

Conclusion

The BMD in young healthy adults is associated with physical exercise, independent of sex and s-25[OH]D status. A sufficient s-25[OH]D status was systematically associated with a higher BMD for all levels of exercise. For both sexes and vitamin D levels exercise was equally positively associated with BMD.

Comparison of nutritional intake, body composition, bone mineral density, and isokinetic strength in collegiate female dancers

This study compared nutritional intake, body composition, bone mineral density, and isokinetic strength by dance type in collegiate female dancers. The study subjects included Korean dancers (n=12), ballet dancers (n=13), contemporary dancers (n=8), and controls (n=12). Nutritional intake was estimated using the Computer Aided Nutritional Analysis Program. Body composition and bone mineral density were measured using dual-energy X-ray absorptiometry. Isokinetic knee joint strength was measured by Cybex 770-NORM. All statistical analyses were performed by SAS 9.2. Means and standard deviations were calculated using descriptive statistics. One-way analysis of variance was applied to evaluate nutritional intake, body composition, bone mineral density, and isokinetic strength differences. Duncan multiple range test was used for post hoc testing. A level of significance was set at P<0.05. The study results indicated no significant differences in nutritional in-take among dancer types. Despite no significant differences in body composition among dancer types, contemporary and ballet dancers had lower body fat percentages than controls (P<0.05). No significant differences were seen in bone mineral density and bone mineral contents among dancer types. No significant differences were found in isokinetic strength in right or left knee flexion and extension at 60°/sec (P<0.05). There were significant differences in body composition and isokinetic strength between dancer groups and the control group. Further studies of different professional dance type and more scientific methods of dance training are needed.

Etiology and body area of injuries in young female dancers presenting to sports medicine clinic: A comparison by age group

INTRODUCTION

Improving knowledge regarding injuries sustained by pediatric dancers is important in order to better understand injury risk. The aim of this study is to analyze dance injury etiology and body area by age in a cohort of young female dancers presenting to a pediatric sports/dance medicine clinic.

METHODS

The cross-sectional epidemiological study of a 5% probability sample of dancers evaluated between 1/1/2000 and 12/31/2009 with a musculoskeletal injury requiring physician evaluation. A total of 2,133 charts were reviewed from which 171 female dancers 8-17 years old (mean age 14.7 years) were identified. Data were stratified by age, < 12 years and ≥ 12 years, and analyzed based on injury body area, type, and etiology. Fisher's exact test was used to determine statistical significance.

RESULTS

Injuries sustained by dancers in the younger age category (< 12 years) were largely to the foot-ankle/lower leg/knee (93.3%) versus thigh-hip/spine/upper extremity (6.7%). In comparison, dancers in the older age group (≥ 12 years) had a large proportion of injuries to the foot-ankle/lower leg/knee (67.3%) as well, but had a notably larger fraction of injuries to the thigh-hip/spine/upper extremity (32.7%; p = 0.04). Approximately two-thirds of the injuries sustained in the younger age group (< 12 years) were classified as bony. In comparison, injuries in the older age group (≥ 12 years) were roughly half bony and half soft tissue (51.3% and 48.7%, respectively; p = 0.29). Most injuries were overuse in etiology for both younger and older age groups (86.7% and 82.1%, respectively; p = 1.00). Through puberty, there was a decline in the injuries to the foot-ankle/lower leg/knee. Conversely, there was an increase in the thigh/hip-pelvis/spine/upper extremity injuries through growth.

CONCLUSIONS

Injuries to young female dancers in this study cohort were mostly categorized as overuse in etiology, and differed by the age group and the body area. Increased information regarding dance injuries can help guide future injury prevention efforts.