Review of ‘Physical activity, body composition and bone density in ballet dancers’

‘Physical activity, body composition and bone density in ballet dancers’ is a scientific research piece carried out by Wouter D. Van Marken Lichenbelt, Ramon Ottenheijm, Klass R Westerterp (of the department of Human Biology, University of Limburg, PO Box 616, 6200 MD Maastrict, The Netherlands) and Mikael Fogelholm (of the UKK-Institute, PO box 30, FIN – 33500, Tampere, Finland).  The findings were received 15.10.1994, revised 14.12.1994 and accepted 30.1.1995.

This piece looks to analyse factors which affect bone density in female ballet dancers. The factors they examine are training history of the dancers, calcium intake, body composition (% of fat, bone and muscle in the body), total body bone mineral density, site specific bone mineral density (whether where they live can affect it) and bone mineral content.

The study used 24 female ballet dancers enlisted from Dutch ballet companies. The dancers had a mean age of 22.6 years. None of the participants were using contraceptive pills. 29 female, non-dancer, students served as a control group.

The team used questionnaires to determine the dancer’s training history, age of menarche (their first period) and how many periods they had over the past 12 months. The tests were carried out on the dancers 2 weeks after menstruation (however, this only the case for the dancers who have a normal number of periods in one year i.e. 9-14 cycles) Their calcium intake by 7d dietary records (7 days), their bone mineral content by duel-energy X-ray absorptiometry, their total body water by H2 dilution, their extra cellular water by bromide dilution and their body fat by underwater weighing.  An oral interview was carried out to determine whether the dancers had anorexia nervosa or bulimia nervosa. The dancers had a significantly lower Body Mass Index (BMI) than average.

1)    The dancers had significantly lower % body fat.

2)    The dancers had comparable fat free mass to the non-dancers.

3)    The dancer’s mean total bone mineral density was considerably higher than that of a reference population.

4)    No relationship was found between age, the age they began dancing, the total years they have been dancing, their calcium intake and their bone mineral density (total and site specific)

5)    None of the dancers had anorexia nervosa or bulimia nervosa according to criteria laid out by the American Psychiatric Association, 1987.

6)    7/24 dancers had menstrual disorders (four or less cycles a year)

Therefore, the research shows that ballet dancers have in fact a high level of bone mineral density despite the fact that they have/do many things which have a negative effect on bone mineral density. Such as: they do chronic, energetic exercise, they have low dietary intake and body mass and they often suffer with hormonal imbalance.

The team who carried out the research believe the reason for this outcome is due to the fact that dancing is a weight baring exercise which has a positive effect on bone mineral density.

I believe this research to be relevant to my inquiry because it is looking into possible health risks dancers could face by eating little and exercising lots. Again, this research was carried out with ballet dancers as the participants and the participants of my inquiry will not currently be ballet dancers. Therefore, it should be said that this research is less relevant to my inquiry that if the same tests had been carried out on jazz dancers or showgirls. However, I think that the results shown can give us an insight to how healthy other dancers’ bodies are. We too partake in weight baring exercise which keeps our bone mineral density high and in most cases we are not as thin as the majority of ballet dancers, therefore, we have on average a higher body mass and higher calorie intake. This means that our bone mineral density should be rather high.

Some issues raised by the research need to be addressed in connection to my inquiry. The first is the fact that the dancers had very low body masses and % body fat compared to the non-dancers. This of course means they are a lot thinner than the average person which is un-surprising. However, the entire reason I chose this piece was because it looks at the effects of what being so thin does to a dancer on the inside not the outside. It was positive to see that none of the dancers were suffering from an eating disorder. However, the fact that seven dancers out of the 24 had menstruation disorders is worrying. When a person’s body is very light they stop having periods because their bodies would not be able to support a baby. This could leave the dancers infertile.

“Women that have suffered from an eating disorder, or who exercise a great deal may experience a cessation of menstruation, otherwise known as amenorrhea, but there can be some long term consequences that will affect fertility.” http://weightgain.lifetips.com/cat/61224/health-risks-of-being-underweight/index.html

I trust this research because it was carried out thoroughly and all the tests were carried out fairly with a good explanation as to how they did each test and why. The downside to this research is that it was carried out 17 years ago. This means that perhaps the methods used are out of a date and so if the exact same research was carried out now the results may be different.