Relatively high bone mineral density in Chinese adolescent dancers despite lower energy intake and menstrual disorder

Central obesity may affect bone development in adolescents: association between abdominal obesity index ABSI and adolescent bone mineral density

PURPOSE

Previous studies have suggested that obesity defined by body mass index(BMI) is a protective factor for bone mineral density(BMD), but have overlooked the potential influence of different types of obesity. This study aims to evaluate the correlation between abdominal obesity index A Body Shape Index(ABSI) and adolescent bone density, and analyze the relationship between abdominal obesity and bone metabolism.

METHODS

A total of 1557 adolescent participants were included in NHANES from 2007 to 2018. Calculate the ABSI using a specific formula that takes into account waist circumference and BMI. A weighted multiple linear regression model is used to evaluate the linear correlation between ABSI and BMD. Forest plots are used to analyze the correlations between subgroups, and cubic splines are limited to evaluate the nonlinear correlations and saturation effects between ABSI and BMD.

RESULTS

After adjusting for confounding factors, there was a significant linear correlation (P < 0.01) between ABSI and femoral BMD, both as a continuous variable and an ordered categorical variable. The restrictive cubic spline curve indicates a significant nonlinear correlation and saturation effect between adolescent ABSI and BMD.

CONCLUSION

Research has shown a significant negative correlation between ABSI and BMD at the four detection sites of the femur, and this correlation may vary slightly due to age, race, family income, and different detection sites. The research results indicate that compared to overall body weight, fat distribution and content may be more closely related to bone metabolism.

Low Body Fat Percentage and Menstrual Cycle Disorders in Female Elite Adolescent Dancers

Introduction: The menstrual cycle is an important indicator of health in female athletes. Female elite adolescent dancers are expected to control their weight while also training intensely, which can lead to menstrual disorders. This study aimed to investigate the relationship between body composition and menstrual status in female elite adolescent dancers. Methods: In total, 131 female elite adolescent dancers (age: 15.9 ± 1.5 years) were enrolled in this study. We measured the height, weight, and body fat percentage (BFP) for each participant and calculated their body mass index (BMI). We gathered information on individual menstruation patterns and the participants' menstrual cycles over the previous year using recall methods. We then compared the differences between dancers with menstrual cycle disorders and those without. Primary amenorrhea was defined as menarche occurring after the age of 15, while secondary amenorrhe was defined as experiencing fewer than 5 or no menstrual periods for at least 3 of the previous 12 months. We conducted a reliability test using the same questionnaire 2 weeks later. Statistical significance was defined as P < .05, and we calculated the effect sizes (d) and 95% confidence intervals (95% CI). Results: The average BMI and BFP were 22.6 ± 3.0% and 19.4 ± 2.2 kg/m2, respectively. Low BFP and low BMI were observed in 51 (38.6%) and 47 (35.6%) participants, respectively. Primary amenorrhea in 3 participants (2.3%) and 29 (22.1%) reported experiencing secondary amenorrhea; they had lower BFP than the dancers who did not experience amenorrhea (P = .041, 95% CI, -2.51 to -0.05). Conclusion: Female elite adolescent dancers in China may have lower BFP and menstrual problems. Given that lower BFP may contribute to the occurrence of menstruation disorders, it is essential to pay an attention to both BFP and the menstruation status in female elite adolescent dancers.

Body Composition, Eating Habits, and Disordered Eating Behaviors among Adolescent Classical Ballet Dancers and Controls

Adolescent classical ballet dancers are nutritionally vulnerable, as they try to retain a lean body shape during a life period of high nutritional requirements due to rapid growth. Studies conducted on adult dancers have indicated a high risk for the development of disordered eating behaviors (DEBs), but research on adolescent dancers remains scarce. The aim of the present case-control study was to compare the body composition, dietary habits, and DEBs of female adolescent classical ballet dancers and their non-dancer same-sex peers. Self-reported questionnaires, namely the Eating Attitudes Test-26 (EAT-26) and a 19-item Food Frequency Questionnaire (FFQ), were used for the assessment of habitual diet and DEBs. The assessment of body composition included the measurements of body weight, height, body circumference, and skinfolds and bioelectrical impedance analysis (BIA). The results indicate that the dancers were leaner than the controls, with lower weight, BMIs, and hip and arm circumferences, leaner skinfolds, and less fat mass. No differences were observed between the two groups regarding eating habits and the EAT-26 scores, but almost 1 out of 4 (23.3%) participants scored ≥ 20, indicative of DEBs. Participants with an EAT-26 score ≥ 20 had significantly higher body weight, BMIs, body circumferences, fat mass, and fat-free mass than those with a score < 20. Adolescents must be educated on nutrition and healthy methods to control body weight through evidence-based information and programs, and whenever appropriate, also through individual counseling by the appropriate health professionals.

Protein, lysine and vitamin D: critical role in muscle and bone health

Optimum body composition in terms of higher muscle and bone mass is crucial for balancing metabolic activities for sustainability of healthy human life. Individuals with lesser muscle mass respond poorly to stressed states such as traumatic injury, sepsis and advanced cancers. Most common diseases like obesity, heart disease, cancer and diabetes can be prevented by muscle mass modification. The nutrients like protein, lysine, calcium and vitamin D play a critical role in the maintenance of muscle mass and bone health. Poor dietary protein quality owing to high amounts of cereals and little animal foods have a marked negative impact on health in resource-limited settings. Lysine intake in developing countries is low mainly due to lesser food intake, consumption of cereals as staple diet and processing loss of lysine. Furthermore, lysine intakes have been shown to be marginal in low socio-economic groups which are of even greater concern. Cereal-based diets and cereal-based food subsidy programs offer low quality proteins and pose a risk of quality protein deficiency. Diets lacking in vitamin D contribute to vitamin D deficiency which is prevalent in epidemic proportions in large part of the world. Cereal-based vegetarian diets are responsible for lesser bioaccessibility of calcium as well. For obtaining optimal health, optimal muscle mass should be maintained at a younger age, which can be achieved by improving nutritional quality of diets. Dietary and medicinal supplementation of lysine, calcium and vitamin D may improve the body composition of young adult women in the form of proportionally more muscle mass, bone mass and lesser fat mass, which in turn, may prove helpful in improving general well-being, physical fitness as well as preventing metabolic diseases in developing countries.

Body Mass Index and Menstrual Patterns in Dancers

Questionnaires were distributed to investigate body mass index (BMI) and menstrual patterns in female dancers aged 12 to 17 years. The study cohort consisted of 105 dancers, mean age 14.8 ± 1.1 years, and mean BMI 19.5 ± 2.3 kg/m². In all, 92% were healthy weight for height. First menses age ranged from 10 to 15 years (mean 12.9 ± 1.1 years). A total of 44% reported irregular menses; of those, 14% described irregularity as "every other month," 37% as "every 3 months," and 49% as "skips a month occasionally." A total of 36% of the dancers stop getting their menses during times of increased activity/dance, and 30% have gone >3 months at any time without getting their menses. A significant negative correlation between BMI and age of first menses was found with lower BMI associated with increased age of first menses (linear regression, β = -0.49, P = .021). This study supports an association between BMI and age of menarche among young female dancers. Given bone health reliance on hormonal milieu in female dancers, future research is warranted.

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.

Prevalence of low bone mineral density in female dancers

BACKGROUND AND OBJECTIVE

While some authors report that dancers have reduced bone mineral density (BMD) and increased risk of osteoporosis, others have stressed the positive effects of dance training on developing healthy BMD. Given the existing controversy, the aim of this systematic review was to examine the best evidence-based information available in relation to female dancers.

METHODS

Four databases (Web of Science, PubMed, EBSCO, Scopus) and two dance science journals (Journal of Dance Medicine and Science and Medical Problems of Performing Artists) were searched for relevant material using the keywords "dance", "ballet", "BMD", "bone density", "osteoporosis" and "female athlete triad syndrome". A total of 257 abstracts were screened using selected inclusion (studies involving bone measurements in dancers) and exclusion (editorials, opinion papers, chapters in books, narrative reviews and non-English language papers) criteria according to PRISMA guidelines. Following the above screening, a total of 108 abstracts were identified as potentially relevant. After the exclusion of conference proceedings, review papers, studies focusing only in male dancers and studies in which dancers' information were combined with other athletes, the eligible papers were subsequently assessed using the GRADE system and grouped according to: (1) prevalence of low BMD and associated factors, (2) incidence of low BMD and risk factors, (3) prevention/treatment of low BMD in dancers, and (4) other studies.

RESULTS

Of the 257 abstracts that were initially screened, only 35 studies were finally considered. Only one of these 35 was of high quality, while the remaining 34 were of relatively low quality. Seven studies reported prevalence of low BMD and associated factors, 10 reported associated factors with no prevalence data, while one reported prevalence with no associated factors data. One study cited risk factors, while another one elaborated on the treatment of low BMD in dancers. The remaining 15 studies were classified as "other studies".

CONCLUSIONS

It remains unclear whether low BMD is prevalent in female dancers. The present review highlights the need for high-quality BMD research in this area.