Date Published: July 5, 2017
Publisher: Public Library of Science
Author(s): Tânia Amorim, George S. Metsios, Matthew Wyon, Alan M. Nevill, Andreas D. Flouris, José Maia, Eduardo Teixeira, José Carlos Machado, Franklim Marques, Yiannis Koutedakis, Carlos M. Isales.
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.
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.
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).
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). 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.
Low bone mineral density (BMD) and osteoporosis are of major public health concern . These conditions are characterised by low BMD and low bone mineral content (BMC), which lead to a fragile skeleton and increased risk of osteoporotic fractures . Physical exercise is a key factor against the development of these conditions [2, 3], particularly weight-bearing exercises during the developmental years .
Dance students had significantly lower body weight and height than controls (p<0.001 and p = 0.001, respectively; Table 2). By the time of the assessment, two dance students and 15 controls had reached menarche (one dancer had oligomenorrhea, whereas the other dancer and all 15 controls had regular menses). A significantly higher number of dance students were at Tanner sexual pubertal development I (67.6%), while controls were at stage IV (40.0%), p<0.001. There was no significant difference in terms of calorie intake between groups, but daily calcium intake was significant greater in dancers (p = 0.03). To our knowledge, this is the first study which examined levels of areal and volumetric measures of bone mass in pre-pubertal female vocational dance students prior to undergoing any serious professional training. Our data revealed that first year vocational dancers demonstrated significantly lower adjusted BMD at the forearm, and significantly lower adjusted BMAD and BMD at the FN compared to aged- and sex-matched controls. It could be argued, therefore, that by the time our volunteers were selected to receive professional dance training they already demonstrated inferior bone mass measurements than controls. Prior to commencing full professional dance training, first year female vocational dance students demonstrate low bone mass parameters compared to aged- and sex-matched controls. Therefore, the low BMD values reported in professional dancers might have their genesis during the growing years. Further longitudinal research is required to ascertain how bone mass parameters change with time throughout professional dance training. Source: http://doi.org/10.1371/journal.pone.0180639