A Comparison between Two Studies of External Rotation and Turnout.
The term ‘turnout’ is used in the dance world to describe external rotation (ER) of the femur in the hip joint. Adequate turnout is a fundamental necessity both anatomically and technically for success as a classical ballet dancer. The range of ER is determined by the shape of the hip joint and the strength and flexibility of the surrounding muscles and ligaments. The skeletal capacity of the hip joint is generally formed by the age of 12 years, resulting in a ‘fixed’ range of motion (ROM).
Presuming dancers have a greater range of turnout than the general population, then the hypothetical question is, “does training affect ER?’ or is there some form of natural selection where by only dancers with greater ER make it as professionals. This question is made harder to determine by the simple fact that a systematic protocol for measuring turnout has not yet been established. With a measuring protocol, comparisons could be made between studies paving the way to greater understanding, improvement in training, injury prevention and rehabilitation.
In this paper I will show how two different systems or methodologies can be used in determining the ROM at the hip joint and discuss the reasons, methods and results behind the two scientific studies, exploring their limitations and making possible recommendations for future research in the field of ‘turnout’.
Using various techniques and search engines to find articles on the chosen subject, turnout, (, www.google.com, www. pubmed.gov,www.infotrieve.com and Dance on Disk) as well as general reading on the subject, eight articles of interest involving ROM at the hip joint in dancers and non-dancers were identified. This was then narrowed down to the two with similar aims and objectives. The chosen articles were both original investigations using young pre- professional participants.
Bennell, K., Khan. K. M., Matthews. B., De Gruyter. M., Cook. E., Holzer. K., Wark. J .D. (1999). Hip and ankle range of motion and hip and muscle strength in young novice female ballet dancers and controls. British journal of sports medicine, 33 340-346.
Garrick, J. G., Requa, R. K. (1994) Turnout and training, Medical problems of performing artists, 9(2) 43-49
Note, for this review the interest is only in the section of the study focusing on hip ROM in the first article.
Review of Literature.
Both articles cite several of the same pieces of research from the 1980’s (DiTullio, Micheli and Sammarco) which have shown that dancers have a greater ER than that of non-dancers. Bennell et al. (1999) gives a general overview of the relevant research without going into the specifics of different studies. Garrick et al. (1994) on the other hand provides a large comprehensive literature review going into depth with regards to methods used and discussing their results, however rather than giving the data the paper seems to assume results without an explanation of how these conclusions arose. Garrick et al. (1994) “ Unfortunately, the authors provided insufficient data to allow calculation of external rotation for dancers in the prone position, although that number would appear to be around 41°.” (p.44)
Aims and Objectives.
Both of the studies reviewed were concerned with similar ideas. Bennell et al. (1999) wanted to see if patterns seen in elite dancers present at an earlier age before intensive training (p.341), thus a product of training or selection and also how hip ER in novice ballet dancers compared to that of controls (p.340). Garrick et al. (1999) was interested in the effect of training on ER; does it increase as a result? (p.47)Also on a larger scale than Bennell et al’s, how do dancers compare to that of the general non-dancing population? (p.43)
The two articles chose their methods for the investigation based on modified versions of previous studies enabling them to make comparisons to other data in the same field. Bennell et al (1999 p.341), Garrick et al. (1994 p.45).
Bennell et al. (1999) is a cross sectional study using 77 female dancers aged 8-11 years with an age and residential postcode matched selection of 49 controls to insure similar socio-economic back grounds. The controls were screened to exclude subjects who had participated in more than three months of ballet or gymnastic training and if they took part in more than two hours worth of organised sporting activities a week, which seemed appropriate. The dancers were recruited from 35 local ballet schools, training between one and ten hours per week. All subjects were pre or peri-pubertal. The choice of age group was relevant to the aim of the study as all participants were within the desired age range, however the standard of the dancers is not described in great detail. It is stated that the interquartile range is grade 2 (p.341) but without the information of which syllabus’ used etc, it is difficult to determine the exact accomplishment standard. A table of the participant’s characteristics is included in the article. (p.341)
One person performed all the measurements per subject without intervening. Active turnout was measured in two ways, firstly by lying supine and taking the measurement of ER and internal rotation (IR) of the right hip with the aid of an inclinometer (figure 1.) and then weight bearing using a specially constructed protractor (figure 2.), measuring both hips. I personally believe that rotational disks may be more appropriate to eliminate friction however the degree intervals are 5°, which would cause less accuracy. Participants were given practise time but no formal warm up before the tests. (p.341-342). Bennell et al. (1999) provides placement guidelines for the inclinometer and protractor in the article. The median of three measurements were taken for the active ER test using the inclinometer and the median of five attempts used for statistical analysis in the standing active test using the floor protractor. (p.342). Pearson r-values are given for test-retest and inter test reliability. (p.344).
Fig. 1 Example of an inclinometer.
Fig. 2 Example of a floor protractor
Garrick et al. (1999) tested 591 accomplished female dancers between the ages of 9 and 19, over a three year period at a large pre-professional ballet school’s summer programme. (p.45). The age range was chosen so that direct comparisons could be made to the results of a previous study outlining ‘normal’ values for the general population. Staheli, L. T., Wyss, C. M., King, C. (1985). Garrick et al. also wished the experiment to be as large as possible as it was stated that limitations of several past studies could be due to small subject pools and so a cross section of age and skill could be measured. (p.47). Hence the choice of pre-professional dancers, they were of a good technical standard but easily accessable under the same roof. Many testers were used (although exact figures are not provided) and they were allowed to use their hand to add gentle pressure to the limb whilst the measurement took place. (p.44-45). However there is no way of controlling how much pressure was used.
Measurements for passive hip ER where taken using a goniometer (see figure 3.) of both hips whilst the participant was lying in a prone position. (p.45) Unfortunately in the paper no measuring guidelines are given to explain neither precisely how the tests were performed nor how to prevent the participants from using their abductors to assist the movement. Repeat testing is unclear however in the ‘discussions’ section it is commented on that little or no time was available to always do repeat measurements. (p.47) There is no information given for the testing reliability or any form of statistical analysis involved.
Figure 3. Example of a goniometer
Any replication of the Garrick et al. (1994) Paper would be near to impossible due to the lack of information, although protocols were similar to Saheli et al’s (1985) it is still not explained sufficiently what those similarities were, or were not.
The results for both papers were interesting. Bennell e al. (1999) Presented a complete representation of all data collected in the form of tables, (p.341 & 344) appropriate for the information displayed and easy to interpret and understand. It was found that there was no significant difference of turnout between the dancers and controls, however the dancers actually had less hip ER but greater non-hip ER. In answer to their question of whether the degree of hip ER and turnout found in elite dancers was a product of training or selection, the data presented shows that there is no significant correlation between training years / weekly training hours and hip ROM. (p.344)
Garrick et al’s (1994) results are presented in the form of tables and line graphs combining both their results and those of the Staheli et al (1985) paper. (p.45-48) This makes it easy for the reader to compare the hip ROM for both dancers and non-dancers, fulfilling the aim of the experiment. The tables also completely break down the information by age and skill proficiency for accessible comprehension, showing that the dancers hip ER increased with age and skill level. However these results still fell within the range of ‘normal’ ROM values set out by Staheli et al.
In the paper by Bennell et al. (1999) the results are discussed (p.344) explaining their findings and relating them back to the problem. They find that novice dancers do not have a greater hip ER although other previous studies have concluded that professional dancers have a greater ROM than the non-dancing population. No excessive speculation is given however the question remains un-answered to whether this could be due to intensive training or a selection bias.
On the other hand, in Garrick et al’s. (1994) paper a large proportion of the discussion centres around the limitations of the study (p.46). Relationships of the results are made to Staheli et al’s (1985) study and how dancers can be considered to be in the ‘normal ‘ range but there is no mention of a comparison to any of the studies cited in the introduction. The vagueness in the method section leads to concerns towards the credibility of the results.
Both papers agree that due to the nature of their studies, (small cross -sectional or prevalence), more research needs to be done especially longditudal studies in the area. These will en-able us to determine the effects of training on ROM and hip ER as well as showing if the dance profession have a form of natural selection.
In conclusion I believe these papers both bring interesting views and results to light. The Bennell et al. (1999) method was meticulously thought out and executed and Garrick et al’s. (1994) idea certainly deserves more investigation, however they just confirm that a systematic protocol for measuring must be established.
Perhaps qualitative research could be a useful tool to determine functional turnout in the class, longitudinal studies to show the effects of training. Of course all avenues need to be explored. When turnout is discussed many variables need to be accounted for, is measuring passive and active ROM enough? A dancer has to be able to use their ‘turnout’, should measurements focus solely on hip ER or does non-hip ER such as rotation at the knee and ankle calculate as ‘turnout’? Are measurements more accurate when studying active or passive turnout? And which of these is the most appropriate in the context of dance.
Bennell. K., Khan. K. M., Matthews. B., De Gruyter. M., Cook. E., Holzer. K., Wark. J. D. (1999). Hip and ankle range of motion and hip and muscle strength in young novice female ballet dancers and controls. British journal of Sports Medicine, 33 340-346.
Bennell. K., Khan. K. M., Matthews. B., Singleton. C. (2001). Changes in hip and ankle range of motion and hip muscle strength in 8-11 year old novice female ballet dancers and controls: a 12 month follow up study. British journal of Sports Medicine, 35,54-59
Garrick., G., Requa. R. K. (1994) Turnout and training, Medical Problems of Performing Artists, 9(2) 43-49
Grieg, V. (1994). Inside ballet technique: separating fact from fiction in the ballet class. Highstown, NJ: Princeton book company
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Khan, K. Roberts, P. Nattrass, C. Bennell, K. Mayes, S. Way, S. Brown, J. McMeeken, J. Wark, J. (1997). Hip and ankle range of motion in elite classical ballet dancers and controls. Clinical journal of Sports Medicine, 7(3), 174-9
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Martin, S. C. Marquez, F. A. Ordonio, M. A, Allen, D. D. (1998). Measuring functional range of motion in ballet dancer’s hips. Journal if Dance medicine and Science, 2(2), 56-62
Staheli, L.T. Wyss, C. M. King, C. (1985). Lower extremity rotational problems in children. Normal values to guide measurement [American volume]. Journal of Bone and Joint Surgery, 67(1), 39-47