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Postural adjustments in young ballet dancers compared to age matched controls
Accepted Manuscript Postural Adjustments In Young Ballet Dancers Compared To Age Matched Controls Denise H. Iunes, Iara F. Elias, Leonardo C. Carvalho, Valdeci C. Dionísio PII:
S1466-853X(15)00036-X
DOI:
10.1016/j.ptsp.2015.04.004
Reference:
YPTSP 664
To appear in:
Physical Therapy in Sport
Received Date: 16 July 2014 Revised Date:
27 February 2015
Accepted Date: 28 April 2015
Please cite this article as: Iunes, D.H., Elias, I.F., Carvalho, L.C., Dionísio, V.C., Postural Adjustments In Young Ballet Dancers Compared To Age Matched Controls, Physical Therapy in Sports (2015), doi: 10.1016/j.ptsp.2015.04.004. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT POSTURAL ADJUSTMENTS IN YOUNG BALLET DANCERS COMPARED TO AGE MATCHED CONTROLS Denise H. Iunesa*, Iara F. Eliasa, Leonardo C. Carvalhoa, Valdeci C. Dionísiob Physiotherapy Course, Federal University of Alfenas, Brazil
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Physiotherapy Course, Federal University of Uberlândia, Brazil
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Correspondence to: Denise Hollanda Iunes. E-mail: [email protected]
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Jovino Fernandes Sales, 2600 Avenue
Alfenas, Minas Gerais, Brazil 37130-000 +55 35 32922377
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Iara F. Eliasa, Leonardo C. Carvalhoa
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Jovino Fernandes Sales, 2600 Avenue, Bairro Santa Clara Alfenas, Minas Gerais, Brazil, 37130-000
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+55 35 32922377
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Valdeci C. Dionísiob
R. Benjamin Constant, 1286 - Bairro Aparecida Uberlândia, Minas Gerais, Brazil, 38400-678 +55 34 91072816
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POSTURAL ADJUSTMENTS IN YOUNG BALLET DANCERS COMPARED TO
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AGE MATCHED CONTROLS
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ACCEPTED MANUSCRIPT Abstract
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Objectives: The purpose of the study was to use photogrammetry to evaluate the posture
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of ballet practitioners and compared to age-matched control. Design: One hundred
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eleven 7- to 24-year-old female volunteers were evaluated and were divided into two
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groups: the ballet practising group (n = 52) and the control group (n = 59), divided into
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three subgroups according to age and years of ballet experience. Results: Dancers with
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practice time ballet 1 to 3 years compared to controls of the same age shows alteration
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in External Rotation Angle (P<0.05). Dancers with practice time 4 to 9 years shows
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alteration in Lumbar Lordosis, Pelvis Tilt Angle and Navicular Angle Right and left
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(P<0.05). Dancers with practice time over
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Rotation and Navicular Angle Left (P<0.05) Conclusions: Research shows there are
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differences between dancers and controls. In the groups 1 to 3 years and over 9 years of
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experience, the External Rotation Angle is greater. In the group 4 to 9 years of
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experience the Lumbar Lordosis Angle is greater and Pelvis Tilt, Navicular Angle Left
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and Right are smaller. In more than 9 years of ballet experience, the Navicular Angle
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Left is smaller.
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Key words: Ballet; Posture; Physiotherapy; Photogrammetry
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Introduction
23 Classical ballet presents movements that do not overload the body; however, the
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extreme movement amplitudes may contribute to changes in both biodynamics and
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posture (Gupta et al., 2004). The classical technique is always performed in en deors
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(external rotation of the hip), which contributes to a higher elevation of the lower limb a
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la second (in hip abduction), which is essential to the performance of all classical
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technique and movements (D’Hemecourt & Luke, 2012). When the dancer has limited
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external rotation, there are several compensatory mechanisms to achieve the desired
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rotation, including external rotation of the tibia while the knee is flexed, which is
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associated with an anterior pelvic tilt. However, these compensations can increase the
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risk of injury (D’Hemecourt & Luke, 2012). Although, dancers exhibit lower peak
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ground-reaction forces than other athletes, they generally attenuate landing force over a
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longer period of time. The dissipation of impact forces may help this population avoid
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serious lower extremity injuries (Orishimo, Kremenic, Pappas, Hagins & Liederbach,
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2009).
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The posture required in the practise of classical ballet can be associated with the
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development of a pattern of musculoskeletal adaptations such as spine hyperextension
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and increased hip movement amplitude and overload during jumps and landings on a
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single foot (en pointe) (D’Hemecourt & Luke, 2012). In the full pointe position requires
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ankle plantar flexion with the toes in a neutral position relative to the longitudinal axis
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of the foot. In this position the intrinsic muscles of the foot and the muscles of the ankle
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are needed to be strong. In addition, the five basic positions in ballet are based in
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turnout or outward rotation of the feet. The ideal turnout demonstrates 180o of external
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rotation starting at the hips and resulting in the feet being easily placed in an 180o
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position on the floor (Kadel, 2006), which contributes to the execution of the ballet
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classic technique. The mechanism of postural changes and their compensations are important for
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understanding the relationship between a dancer's posture and injuries (Macintyre &
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Joy, 2000; Solomon, Brown, Gerbino & Micheli, 2000; Bruyneel, 2011; Hincapié,
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Morton & Cassidy, 2008).
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The practise of classical dance typically begins during childhood, which the
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evidence suggests that musculoskeletal injury is an important health issue for dancers at
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all skill level (Hincapié, Morton & Cassidy, 2008). Changes in the alignment of the
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longitudinal axis of the long bones before the age of 11 may contribute to changes in
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posture (D’Hemecourt & Luke, 2012). However, these aspects are seldom studied
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(Solomon, Brown, Gerbino & Micheli, 2000; Bruyneel, 2011; Hincapié, Morton &
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Cassidy, 2008). Inadequate adaptation of the musculoskeletal system can result in injury
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(Arendt & Kerschbaumer, 2003). The incidence of injury may be related to an increase
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in the performance effort of the ballet practitioner (Shah, 2008) and contemporary
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dancers (Angioi et al, 2009), years of dancing experience, practise frequency, training
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intensity (Solomon, Brown, Gerbino & Micheli, 2000; Bruyneel, 2011; Hincapié,
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Morton & Cassidy, 2008; Shah, 2008), repetitive movements (Macintyre & Joy, 2000;
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Bruyneel, 2011), inappropriate training prior to bone maturity (Amari et al., 2009), lack
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of flexibility and range of motion (Macintyre & Joy, 2000) and poor physical fitness
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levels (Angioi et al., 2009). Moreover, factors such as space, temperature, ventilation
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and floor type may contribute to musculoskeletal injuries (O’Loughlin, Hodgkins &
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Kennedy, 2008). However, most of these studies did not correlate the aforementioned
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ballet. Postural assessment may reveal whether participation in ballet induces
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adaptations and identify which regions of the body are most affected by these
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adaptations, providing important information for the understanding of injuries that
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affect the musculoskeletal system of this population.
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Thus, the aim of this study was to use photogrammetry to quantitatively evaluate the posture of ballet practitioners and compared to age-matched control
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Method
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Participants
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One hundred eleven female volunteers participated in this study and the subjects
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and their parents signed an informed consent that had been approved by the Ethics
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Committee on Human Beings under Protocol no. 085-2/2010. The volunteers were
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divided into two groups: the ballet practising group (n = 52) and the control group (n =
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59). Volunteers within the ballet practicing group were further divided into three sub-
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groups according to their years of ballet experience: Group 1, from 1 to 3 years of
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experience; Group 2, from 4 to 9 years of experience; and Group 3, more than 9 years of
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experience (Table 1). The control group volunteers were further divided into three age,
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weight, and height-matched subgroups. Volunteers in the ballet practicing groups
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participated in two to three 60- to 90-minute ballet classes per week. All dancers
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belonged to the same vocational institution, had practised dance for at least one year and
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were at least 7 years old. The control volunteers belonged to two regular schools.
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Volunteers who were related or had a history of lower limb or spine fracture were
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excluded from the study. No injury data was collected.
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ACCEPTED MANUSCRIPT Considering the Pelvis Tilt Angle as the main variable, a power effect of 1.00
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and an effect size of 1.80 (α=0.05) were obtained from a sample size of 111 subjects
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divided in six groups as described earlier. The GPower® 3.1.7 software (Franz Faut,
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Universität Kiel Germany, 2008) was used for this analysis (Cohen, 1988, Nakagawa,
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S.& Cuthill, 2007).
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TABLE 1 TO BE INSERT AROUND HERE
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A SONY® Cyber-shot digital camera with a 7.2 megapixel resolution was
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positioned on a level tripod, parallel to the floor and at a height of one meter, with a
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distance of 2.4 m between the camera lens and the volunteer (Iunes, Bevilaqua-Grossi,
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Oliveira, Castro & Salgado, 2009). The volunteer was positioned standing upright, with
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the upper limbs beside the body and 0.075 m between the medial malleoli. The distance
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between the medial malleoli was maintained with the aid of ethyl vinyl acetate (EVA)
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marker. The volunteers were photographed in an anterior view (frontal plane) and a
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right lateral view (sagittal plane).
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For the photographic record of the feet, the camera was positioned on a level
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tripod, parallel to the floor and at a height of 0.45 m, with distance of 0.24 m between
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the camera lens and the podoscope. The digital images were stored and then analysed on
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a personal computer using ALCimagem -2000 Version 1.5 software (Lima, Barauna,
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Sologurem, Canto & Gastaldi, 2004).
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Procedure
ACCEPTED MANUSCRIPT To take photographs in the sagittal plane (Figure 1A), the lower limbs were
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positioned in parallel, and the following anatomical points were marked with an orange
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flexible rod (length = 0.06 m) by the same assessor: the anterior superior iliac spine
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(ASIS); the posterior inferior (PIIS); the spinous processes of T12, L3 and L5; the greater
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trochanter; the fibular head; and the lateral malleolus. The following angles were
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measured: lumbar lordosis (LL), which is formed by the intersection of the direct line
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connecting the T12 spinous process with the L3 spinous process and the direct line
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connecting the L3 spinous process with the L5 spinous process; Pelvic tilt, which is
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formed by the intersection of the direct line connecting the PIIS with the ASIS and the
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horizontal plane (Iunes, Bevilaqua-Grossi, Oliveira, Castro & Salgado, 2009); and knee
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flexion (KF), which is formed by the intersection of the direct line connecting the
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greater trochanter with the fibular head and the direct line connecting the fibular head
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with the lateral malleolus.
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To take photographs in the frontal plane (Figure 1B), the following anatomical
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points were marked on the skin of the volunteers with white self-adhesive labels: the
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ASIS, the centre of the patella, the tibial tuberosity and the medial malleolus (a flexible
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plastic rod was used for this location). The following angles were measured: Q Angle
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(Smith, Hunt & Donell, 2008) and Knee Angle (KA) (Iunes, Bevilaqua-Grossi, Oliveira,
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Castro & Salgado, 2009), formed by the intersection of the direct line connecting the
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ASIS with the tibial tuberosity and the vertical plane.
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To take photographs with the lower limbs in external rotation of the hip (Figure
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1C), the following anatomical points were marked: the medial malleolus (orange
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flexible rod), the first metatarsophalangeal joint (1st MTF) (lateral and superior), the
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navicular tuberosity, and 0.06 m below the medial malleolus. The following angles were
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drawn along the medial edges of the feet; and the Navicular Angle (NA), which is
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formed by the intersection of the direct line connecting the first MTF (lateral) with the
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navicular tuberosity and the direct line connecting the navicular tuberosity with the
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marker located 0.06 m below the medial malleolus.
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FIGURE 1 TO BE INSERT AROUND HERE
To take photographs of the forefoot, hindfoot and arch, the participant stood on a
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podoscope with the upper limbs beside the body and the lower limbs separated by an
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EVA marker (width = 0.075 m). To evaluate the forefoot, the following anatomical
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points were marked: the heads of the first and fifth metatarsals. To evaluate the
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hindfoot, the following anatomical points were marked: the calcaneal posterior
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tuberosity (0.03 m above the floor), a second point 0.04 m above the first (i.e., 0.07 m
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above the floor), a third point at 0.13 m above the floor and a fourth point at 0.22 m
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above the floor, as in Figure 1C. The following angles were measured: Forefoot Angle
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(FA), which is formed by the intersection of the direct line connecting the first
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metatarsal head with the fifth metatarsal head and the horizontal plane; and Hindfoot
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Angle (HA), which is formed by the intersection of the direct line connecting the first
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point (0.03 m above the floor) with the second point (0.07 m above the floor) and the
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direct line connecting the third point (0.13 m above the floor) and the fourth point (0.22
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m above the floor), as shown in figure 2. To evaluate the plantar arch (PA), the
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following anatomical points were marked: a straight line was plotted across the mid-
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point of the calcaneus foot print perpendicular to the axis of the foot (A), and a straight
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line was plotted across the isthmus of the plantar arch perpendicular to the axis of the
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foot (B) (Staheli, Chew & Corbett, 1987). PA was defined as the length of B divided by
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the length of A. PA values between 0.01 m and 0.03 m were considered normal. PA
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values greater than 0.01 m were considered flat, and PA values less than 0.03 m were
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considered cavoid (Staheli, Chew & Corbett, 1987). The reliability and validity of measurements by photogrammetry was described
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in previous studies (Ribeiro, Trombini-Souza, Iunes & Monte-Raso, 2006; Iunes,
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Bevilaqua-Grossi, Oliveira, Castro & Salgado, 2009; Iunes, Castro, Salgado, Moura,
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Oliveira & Bevilaqua-Grossi, 2005).
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172 Statistical Analyses
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FIGURE 2 TO BE INSERT AROUND HERE The Kolmogorov-Smirnov (KS) test was used to test the data obtained in this
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study for normality. If the data had a normal distribution, the analysis of variance
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(ANOVA) followed by the Tukey-Kramer tests were performed. In case of non-
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normality the data, the Kruskal-Wallis followed by the Mann Whitney was used. For all
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analyses, was considered 5% significance, as calculated using the SPSS v.17.0 software.
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Results
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Analysis: Dancers compared with controls Table 2 shows that when dancers (B1, B2, B3) are compared with their
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respective controls (C1, C2, C3), there was an increase in the angular values of the ER
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of the hip for the dancers in groups B1 and B3 (p <0.01). However, in group B2, the
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angular values of the ER of the hip were similar to those of C2. The LL angle was only
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increased in dancers in group B2 (p <0.01), while the LL angles of dancers in groups B1
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reduced in dancers in group B2 (p <0.01), but the pelvic tilts of dancers in groups B1
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and B3 were similar to those of their respective controls. The positioning of the right
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(FAR, p <0.01) and left (FAL, p <0.01) feet was also reduced in the group B2.
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The other measured variables (i.e., the Knee Angle (RKA and LKA), the Q
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Angle (RAQ and LAQ), the knee flexion angle (KFA), the forefoot positioning (FAR
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and FAL), the hindfoot positioning (HAL and HAR) and the plantar arches) were
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similar among the groups (p >0.05).
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Analysis among the dancer groups
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Postural changes in the external rotation (ER), pelvic tilt (Figure 3) and the right
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forefoot (HAR) (Figure 4) were observed in the comparative analysis among the dancer
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groups (p <0.01). There was a difference in the ER angle among the dancer groups
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(Figure 3): ER was increased in B1 and B3 (160.83° and 159.24°, respectively), while
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ER was decreased in B2 (152.92°). Pelvic tilt was increased (i.e., the pelvis was
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anteverted) in all dancers (Figure 3).
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The angle of the right hindfoot increased steadily among groups B1 (7.65°), B2
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(8.58°) and B3 (11.12°). The results suggest a development of calcaneal valgus over
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time (Figure 4).
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FIGURE 4 TO BE INSERT AROUND HERE
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Discussion This study quantitatively evaluated postural changes in ballet practitioners
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according to years danced and comparing them to age matched controls. Our hypothesis
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was that years of ballet experience would promote postural changes in practitioners
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compared to non-practitioners in different age groups. The results of this study partially
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support this hypothesis because the postural changes were more consistent between the
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B2 and C2 groups. The variables that showed differences between these groups
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(Lumbar Lordosis, Pelvis Tilt, Navicular Right and Left Angles) are very important for
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postural control and may be associated with musculoskeletal injury. The human body's
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centre of mass lies in the centre of the pelvis, and the accuracy of its control is essential
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for accurate classical ballet technique. It was in this region that the main angular
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changes, especially the reduction of Pelvic Tilt and the increase of the Lumbar Angles
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(i.e., decreased lumbar lordosis), were identified in group B2. These angular changes
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reduce the stability of the lumbar segment and may make ballet practitioners prone to
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injury (Solomon, Brown, Gerbino & Micheli, 2000; Bruyneel, 2011). Low back pain
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and spine pathologies, such as spondylolisthesis and herniated discs, are commonly
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reported in dancers. This is because the demands of dance involve extreme and
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repetitive lumbar hyperextension (Solomon, Brown, Gerbino & Micheli, 2000;
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Bruyneel, 2011) as well as high impact forces (i.e.big jumps) (Wyon, Twitchett, Angioi,
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Clarke, Metsios, Koutedakis, 2011). Such problems may arise from repetitive training
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movements related to dancing, as well as anatomical features and technical errors
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(Amari et al., 2009).
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Our results reveal that the largest change occurred in the pelvic region, not the
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lumbar region. The positive Pelvic Tilt Angle observed in all volunteers showed the
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to the control group. This change is believed to be related to years of ballet experience
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because volunteers in B1 and C1 had similar Pelvic Tilt Angles, and their age and BMI
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characteristics were similar to those of volunteers in B2 and C2. Therefore, the results
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suggest that the patterns of ballet movements tend to reduce pelvic anteversion, which is
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characteristic of this age group (Whide, 2001; Giglio & Volpon, 2007) or may have
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occurred compensation in other joints (Coplan, 2002) which suggests the need for
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further research.The external rotation of the lower limb in non-dancers becomes fixed
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between the ages of 8 and 11 years (Benell, Khan, Matthews, Singleton, 2001).
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However, this rigidity was not observed in ballet practitioners, suggesting a direct
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influence of training to increase flexibility (Steinberg et al., 2005). External rotation
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unilateral performed by the hip joint is limited to 70° (Thomasen, 1982). External
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rotation beyond 70° is obtained by compensation by other regions of the lower limb
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(Coplan, 2002), such as the tibia, which accounts for 5° of rotation, and the foot, which
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accounts for 15° of rotation, resulting in a total possible external rotation of 180°
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bilaterally (Thomasen, 1982). Forced external rotation, which is a serious training error,
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results in high tensile forces, which, in turn, increase the risk of damage to the posterior
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region of the knee and other structures of the lower limbs (Ryan & Stephens, 1987;
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Hald, 1992; Khan et al., 1995; Schon & Weinfeld, 1996;Orishimo, Kremenic, Pappas,
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Hagins & Liederbach, 2009). The literature reports that this is a common error (Ryan &
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Stephens, 1987; Gilbert, Gross & Klug, 1998). However, when the ballet technique is
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initiated and practiced at an early age, preventive adaptations in the control of
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movements of the hip in the frontal plane are acquired over the years of practice, and
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can help prevent knee injuries (Orishimo, Kremenic, Pappas, Hagins & Liederbach,
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2009). Even professional dancers show a limited movement of the hip in the frontal
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plane which is believed to be derived from higher neuromuscular control and position
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near the joints. Theories of skeletal maturation in general argue that children have more flexible
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joints, and with their growth, flexibility and, consequently, movement amplitude are
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reduced (Moller & Masharawi, 2011; Jansson, 2004). These findings are similar to the
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results observed in the dancers but not those of the control groups. We believe that as
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ballet experience increased, dancers began to show soft tissue adaptation ligament
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flexibility and increased muscle strength (Benell, Khan, Matthews & Singleton, 2001;
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Duthon,
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Hoffmeyer. & Menetrey, 2013), similar to female athletes after puberty (Quatman, Ford,
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Myer, Paterno & Heweet, 2008), or there was compensation in the knee and foot joints
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(D’Hemecourt & Luke, 2012), which resulted in increased external rotation, as seen in
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B3. In the present study we used a large age group which was originally the variability
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of years of ballet practice in groups. Thus it is believed that these skills may also be
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influenced by the different times of musculoskeletal maturation. However, other factors
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could contribute to increased flexibility, such as genetic changes (eg presence of
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ACTN3 XX genotype) (Kim, Jung, Ki, Youn & Kim, 2014). These factors should also
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be considered when interpreting the results presented in the different groups, due to the
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fact that these characteristics were not evaluated in this study.The Navicular Angle of
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both feet was lower in the dancer groups than in the control groups. This difference was
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particularly apparent in the left foot. These findings suggest that the practise of ballet is
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associated with a strengthening of the intrinsic foot muscles (Mulligan & Cook, 2013)
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(Table 1), but these data would be more notable if the increase or change in the arch
Kolo,
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adaptation may be related to the use of pointe shoes, which contributes to the
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maintenance of an isometric contraction of the intrinsic muscles during some postures
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(Mulligan & Cook, 2013), as well as increased strength of the posterior tibial muscle.
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However, training to increase the flexibility of the joints in the forefoot may increase the
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local amplitude and consequently decrease the plantar arch, thus counteracting the
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findings in the Foot Angle.
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The static analysis presented here can be considered a limitation of this study. In
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dynamic conditions, the nervous system can find alternate ways to perform movements
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(Latash, 2012), thus minimizing the impact of the pelvic differences observed in this
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study. However, the aim of this study was to quantify the influence of years of ballet
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experience on the practitioner's posture.
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The limitations of the study is the lack of control of outside activities amongst
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the dancers as well as the large variation in age in our cohort. Additionally the dancers
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are considered recreational rather than elite level.
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Conclusion
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Research shows there are significant differences between dancers and controls.
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In the groups 1 to 3 years and more than 9 years of ballet experience, the External
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Rotation Angle is greater in the dancers. In the group 4 to 9 years of ballet experience
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the Lumbar Lordosis Angle is greater and Pelvis Tilt, Navicular Angle Left and Right
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are smaller in the dancers. In more to 9 years of ballet experience, the Navicular Angle
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Left is smaller.
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Conflict of interest The authors state that there are no conflicts of interest that might have influenced the preparation of this manuscript.
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body composition, flexibility and injury risk with ACE, ACTN3 and COL5A1
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Lima, L.C.O.; Barauna, M.A.; Sologurem, M.J.J.; Canto, R.S.T. & Gastaldi, A.C.
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Nakagawa, S.& Cuthill, I.C.(2007). Effect size, confidence interval and statistical
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significance: A practical guide for biologists. Biological Reviews of the
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O’Loughlin, P.F.; Hodgkins, C.W. & Kennedy, J.G. (2008). Ankle Sprains and instability in dancers. Clinical in Sports Medicine. 27, 247–262.
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Orishimo, K.F.; Kremenic, I.J.; Pappas, E.; Hagins, M.; Liederbach, M. (2009).
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Comparison of Landing Biomechanics Between Male and Female Professional
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Dancers. The American Journal of Sports Medicine. 37, 11, 2187 – 2193.
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Quatman, C. E., Ford, K. R., Myer, G. D., Paterno, M. V., & Heweet, T. E. (2008). The
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effects of gender and pubertal status on generalized joint laxity in young athletes.
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Ribeiro, A.P.; Trombini-Souza, F.; Iunes, D.H. & Monte-Raso, V.V. (2006). Inter and
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intra-examiner reliability of photopodometry and intra-examiner reliability of
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photopodoscopy. Brazilian Journal of Physical Therapy.10, 4, 435-439, Ryan, A.J. & Stephens, R.E. Dance Medicine A Comprehensive Guide. Chicago: Pluribus Press, Inc.; 1987.
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Schon, L. C. & Weinfeld, S. B. (1996). Lower extremity musculoskeletal problems in dancers. Current Opinion in Rheumatology. 8, 130-142. Shah, S. (2008). Caring for the Dancer: Special Considerations for the Performer and Troupe. Current Sports Medicine Reports. 7(3), 128-132.
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Solomon, R.B.A.; Treg Brown, M.D.; Peter, G.; Gerbino, M.D.; Lyle, J. & Micheli, M.D. (2000). The Young dancer. Clinics in Sports Medicine. 19(4), 717-739.
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Staheli, L.T.; Chew, D.D. & Corbett, M.T. (1987). The Longitudinal Arch. The Journal Bone Joint Surgery. 69(3), 426-28.
Steinberg N, Hershkovitz I, Peleg S, Masharawi Y, Heim, M. & Siev-Ner, I. (2005).
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Range of joint movement in female dancers and non dancers aged 8 to 16 years:
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anatomical and clinical implications. The American Journal of Sports Medicine.
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34, 818–823.
422 423 424 425 426 427
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Thomasen, E. (1982). Diseases and Injuries of Ballet Dancers. Arhus, Denmark: Universitetsforlaget I Arhus. Wyon,M.A.; Twitchett,E.;Angioi,M.; Clarke, F. Metsios,G.; Koutedakis, Y.(2001).
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Time Motion and Video Analysis of Classical Ballet and Contemporary Dance Performance. International Journal of Sports Medicine. 32, 1-5.
Whide, T. (2001). Spine: posture, mobility and pain. A longitudinal study from childhood to adolescence. European Spine Journal. 10, 118–123.
ACCEPTED MANUSCRIPT Table 1. Mean values (95 % CI) of sample characteristics Groups (n) B1 (9) Age
B2 (21) B3 (22) B1 (9)
BMI
B2 (21) B3 (22)
Body
Groups (n)
Control (n=59) 11.00 (8.74 – 11.91)
C1 (9)
11.22
C2 (22) C3 (28) C1 (9) C2 (22)
17.14 (15.88 – 18.73) 18.01 (14.91 – 19.42) 17.37 (16.84 – 19.64) 20.03 (18.42 – 20.46)
C3 (28)
mass
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=
EP
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BMI
AC C
429
Ballet (n=52) 11.22 (8.66 – 13.55) 11.55 (9.66 – 12.43) 17.73 (16.56 – 19.26) 19.44 (16.90 – 21.98) 17.52 (16.72 – 18.30) 20.72 (19.91 – 21.52)
p 0.590 0.805
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Variables
SC
428
0.906 0.063
0.190 0.139
index;
ACCEPTED MANUSCRIPT 430 431 432 433
Table 2. Postural analysis between dancers and non-dancers; mean values (95%CI). B1 = 1 to 3 years of ballet experience; B2 = 4 to 9 years of ballet experience; B3 = more than 9 years of ballet experience; C1 = control group 1; C2 = control group 2; C3 = control group 3.
434
Control Pelvis Tilt Anglea Ballet Control Q Angle Righta Ballet Control Q Angle Leftb Ballet Control
External Rotation Angleb
Ballet
TE D
Control Knee Angle Righta
Ballet
Control Knee Angle Leftb
EP
Ballet
Control
Flexion Knee Angleb
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Ballet
Navicular Angle Righta
Navicular Angle Lefta
Forefoot Angle Righta
Control Ballet
Control Ballet
Control Ballet Control
Forefoot Angle Lefta Ballet
C3 vsB3 (o) 158.33 (155.41-161.25) 158.49 (154.95-162.03) 10.14 (7.63-12.65) 13.17 (10.74-15.60) 17.6 (15.01-20.20) 17.66 (15.22-20.08) 15.41 (12.62-18.19) 17.92 (15.70-20.13) 151.00* (146.58-155.42) 159.24 (156.73-161.75) 175.23 (174.70-175.77) 175.57 (174.78-176.36) 175.58 (174.73-176.44) 176.50 (175.85-177.14) 182.40 (180.33-184.48) 185.02 (182.88-187.16) 133.32 (125.88-140.77) 121.47 (113.31-131.22) 139.23* (132.43-146.03) 119.73 (110.39-129.24) 7.07 (6.01-8.12) 7.65 (6.67-8.61) 6.49 (5.47-7.50) 8.47 (7.40-9.54)
F (3,107)
RI PT
Ballet
C2 vsB2 (o) 151.22* (146.83-155.60) 159.86 (156.66-163.06) 15.66* (12.33-18.99) 8.41 (5.68-11.12) 18.09 (14.97-21.19) 18.35 (15.47-21.22) 16.78 (14.06-19.49) 18.67 (15.64-20.69) 153.01 (149.33-156.70) 152.92 (150.19-155.64) 175.21 (174.52-175.89) 175.50 (174.78-176.42) 176.09 (174.84-177.34) 176.22 (176.48-176.95) 181.83 (179.26-184.41) 182.40 (179.54-185.26) 140.83* (135.78-145.88) 125.39 (119.68-131.11) 143.72* (134.65-152.79) 124.04 (116.81-132.27) 8.27 (6.78-9.74) 8.74 (7.12-10.34) 7.66 (6.40-8.91) 6.85 (5.90-7.80)
SC
Control
Lumbar Lordosis Anglea
C1 vsB1 (o) 155.26 (148.17-162.35) 154.77 (151.10-158.44) 8.71 (5.72-11.65) 11.29 (7.47-15.11) 12.53 (8.53-16.52) 16.68 (12.42-21.93) 11.07 (6.62-15.50) 16.55 (13.01-20.07) 142.64* (131.55-153.74) 160.83 (154.11-167.56) 176.67 (175.02-178.32) 175.14 (173.89-176.39) 175.97 (174.16-177.79) 175.50 (174.19-176.80) 179.04 (174.84-183.24) 183.95 (179.10-188.81) 138.40 (128.13-148.67) 115.92 (99.59-132.25) 136.34 (126.84-145.84) 118.76 (111.43-126.09) 9.04 (7.53-10.55) 7.72 (6.50-8.93) 8.03 (5.54-10.62) 7.97 (6.16-9.77)
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Angles
p
3.363c
0.007
4.092c
0.002
0.753
0.586
-----
0.024
-----
0.000
0.638
0.671
-----
0.3377
-----
0.097
5.030c
0.000
6.431
0.000
1.400
0.287
1,810
0.102
ACCEPTED MANUSCRIPT
Ballet Control Ballet
Measures Arch of the foot Rightb
Arch of the foot Leftb a
436
F Value: 2.698
Ballet Control Ballet
8.95 (7.39-10.49) 8.58 (7.06-10.10) 9.78 (8.22-11.27) 7.71 (6.33-9.09) B2/C2 (cm) 0.30 (0.18-0.41) 0.34 (0.20-0.46) 0.24 (0.10-0.36) 0.40 (0.25-0.53)
8.98 (7.53-10.42) 11.12 (9.61-12.61) 8.97 (7.86-10.03) 6.69 (5.25-8.13) B3/C3 (cm) 0.31 (0.21-0.40) 0.34 (0.23-0.44) 0.36 (0.24-0.46) 0.34 (0.23-0.44)
1.959
0.104
3.553
0.005
AC C
EP
TE D
437 438
p
-----
0.855
-----
0.254
– ANOVA Test; b – Kruskal Wallis Test;* - control versus Ballet- pos hoc test. cCritical
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435
Control
9.90 (7.28-12.51) 7.65 (4.71-10.59) 10.21 (8.19-12.19) 9.50 (6.27-12.72) B1/C1 (cm) 0.35 (0.17-0.53) 0.44 (0.25-0.61) 0.36 (0.18-0.54) 0.52 (0.28-0.75)
RI PT
Hindfoot Angle Lefta
Control
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Hindfoot Angle Righta
SC
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439
Figure 1. The angles evaluated in the photographs. Feet were maintained in parallel in
441
(A) and (B) and in external rotation in (C). PT = Pelvic Tilt; LL = Lumbar Lordosis; KF
442
= Knee Flexion; Q = Q Angle; KA = Knee Angle; ER = External Rotation; NA = Foot
443
Angle.
EP AC C
444
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440
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SC
RI PT
445
446
Figure 2. 1A, forefoot marker points; 1B, hindfoot marker points; 1C, plantar arch
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analysis (FA = Forefoot Angle; HA = Hindfoot Angle).
EP
450
AC C
449
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447
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Figure 3. Postural analysis (lumbar lordosis, angle of pelvic tilt, external rotation and
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flexion knee angle) between dancers with varying years of ballet experience. B1 = 1 to
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3 years of ballet experience; B2 = 4 to 9 years of ballet experience; B3 = more than 9
455
years of ballet experience.
AC C
EP
TE D
452
M AN U
SC
RI PT
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456
Figure 4. Postural analysis (Knee Angle, Hindfoot Angle, Foot Angle, Arch of the foot)
458
between dancers with varying years of ballet experience. B1 = 1 to 3 years of ballet
459
experience; B2 = 4 to 9 years of ballet experience; B3 = more than 9 years of ballet
460
experience.
AC C
461
EP
457
ACCEPTED MANUSCRIPT Acknowledgements The authors would like to thank the Adagio Ballet Company, Sagrado Coração de Jesus School and CAZITA for allowing the volunteers’ participation. We would also like to thank the Federal University of Alfenas and The National
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Council for Scientific and Technological Development (CNPq) for their financial
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assistance.
ACCEPTED MANUSCRIPT Highlights
2. 3.
The posture of the dancers changes between four and nine years of ballet practice. Pelvic tilt is reduced in the group of dancers compared to a control group. Lumbar lordosis is reduced in the group of dancers compared to a
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control group.
S1466-853X(15)00036-X
DOI:
10.1016/j.ptsp.2015.04.004
Reference:
YPTSP 664
To appear in:
Physical Therapy in Sport
Received Date: 16 July 2014 Revised Date:
27 February 2015
Accepted Date: 28 April 2015
Please cite this article as: Iunes, D.H., Elias, I.F., Carvalho, L.C., Dionísio, V.C., Postural Adjustments In Young Ballet Dancers Compared To Age Matched Controls, Physical Therapy in Sports (2015), doi: 10.1016/j.ptsp.2015.04.004. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT POSTURAL ADJUSTMENTS IN YOUNG BALLET DANCERS COMPARED TO AGE MATCHED CONTROLS Denise H. Iunesa*, Iara F. Eliasa, Leonardo C. Carvalhoa, Valdeci C. Dionísiob Physiotherapy Course, Federal University of Alfenas, Brazil
b
Physiotherapy Course, Federal University of Uberlândia, Brazil
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a
Correspondence to: Denise Hollanda Iunes. E-mail: [email protected]
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Jovino Fernandes Sales, 2600 Avenue
Alfenas, Minas Gerais, Brazil 37130-000 +55 35 32922377
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Iara F. Eliasa, Leonardo C. Carvalhoa
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Bairro Santa Clara
Jovino Fernandes Sales, 2600 Avenue, Bairro Santa Clara Alfenas, Minas Gerais, Brazil, 37130-000
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+55 35 32922377
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Valdeci C. Dionísiob
R. Benjamin Constant, 1286 - Bairro Aparecida Uberlândia, Minas Gerais, Brazil, 38400-678 +55 34 91072816
ACCEPTED MANUSCRIPT 1
POSTURAL ADJUSTMENTS IN YOUNG BALLET DANCERS COMPARED TO
2
AGE MATCHED CONTROLS
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ACCEPTED MANUSCRIPT Abstract
5
Objectives: The purpose of the study was to use photogrammetry to evaluate the posture
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of ballet practitioners and compared to age-matched control. Design: One hundred
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eleven 7- to 24-year-old female volunteers were evaluated and were divided into two
8
groups: the ballet practising group (n = 52) and the control group (n = 59), divided into
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three subgroups according to age and years of ballet experience. Results: Dancers with
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practice time ballet 1 to 3 years compared to controls of the same age shows alteration
11
in External Rotation Angle (P<0.05). Dancers with practice time 4 to 9 years shows
12
alteration in Lumbar Lordosis, Pelvis Tilt Angle and Navicular Angle Right and left
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(P<0.05). Dancers with practice time over
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Rotation and Navicular Angle Left (P<0.05) Conclusions: Research shows there are
15
differences between dancers and controls. In the groups 1 to 3 years and over 9 years of
16
experience, the External Rotation Angle is greater. In the group 4 to 9 years of
17
experience the Lumbar Lordosis Angle is greater and Pelvis Tilt, Navicular Angle Left
18
and Right are smaller. In more than 9 years of ballet experience, the Navicular Angle
19
Left is smaller.
20
Key words: Ballet; Posture; Physiotherapy; Photogrammetry
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9 years shows alterations in External
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ACCEPTED MANUSCRIPT 22
Introduction
23 Classical ballet presents movements that do not overload the body; however, the
25
extreme movement amplitudes may contribute to changes in both biodynamics and
26
posture (Gupta et al., 2004). The classical technique is always performed in en deors
27
(external rotation of the hip), which contributes to a higher elevation of the lower limb a
28
la second (in hip abduction), which is essential to the performance of all classical
29
technique and movements (D’Hemecourt & Luke, 2012). When the dancer has limited
30
external rotation, there are several compensatory mechanisms to achieve the desired
31
rotation, including external rotation of the tibia while the knee is flexed, which is
32
associated with an anterior pelvic tilt. However, these compensations can increase the
33
risk of injury (D’Hemecourt & Luke, 2012). Although, dancers exhibit lower peak
34
ground-reaction forces than other athletes, they generally attenuate landing force over a
35
longer period of time. The dissipation of impact forces may help this population avoid
36
serious lower extremity injuries (Orishimo, Kremenic, Pappas, Hagins & Liederbach,
37
2009).
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24
The posture required in the practise of classical ballet can be associated with the
39
development of a pattern of musculoskeletal adaptations such as spine hyperextension
40
and increased hip movement amplitude and overload during jumps and landings on a
41
single foot (en pointe) (D’Hemecourt & Luke, 2012). In the full pointe position requires
42
ankle plantar flexion with the toes in a neutral position relative to the longitudinal axis
43
of the foot. In this position the intrinsic muscles of the foot and the muscles of the ankle
44
are needed to be strong. In addition, the five basic positions in ballet are based in
45
turnout or outward rotation of the feet. The ideal turnout demonstrates 180o of external
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38
ACCEPTED MANUSCRIPT 46
rotation starting at the hips and resulting in the feet being easily placed in an 180o
47
position on the floor (Kadel, 2006), which contributes to the execution of the ballet
48
classic technique. The mechanism of postural changes and their compensations are important for
50
understanding the relationship between a dancer's posture and injuries (Macintyre &
51
Joy, 2000; Solomon, Brown, Gerbino & Micheli, 2000; Bruyneel, 2011; Hincapié,
52
Morton & Cassidy, 2008).
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49
The practise of classical dance typically begins during childhood, which the
54
evidence suggests that musculoskeletal injury is an important health issue for dancers at
55
all skill level (Hincapié, Morton & Cassidy, 2008). Changes in the alignment of the
56
longitudinal axis of the long bones before the age of 11 may contribute to changes in
57
posture (D’Hemecourt & Luke, 2012). However, these aspects are seldom studied
58
(Solomon, Brown, Gerbino & Micheli, 2000; Bruyneel, 2011; Hincapié, Morton &
59
Cassidy, 2008). Inadequate adaptation of the musculoskeletal system can result in injury
60
(Arendt & Kerschbaumer, 2003). The incidence of injury may be related to an increase
61
in the performance effort of the ballet practitioner (Shah, 2008) and contemporary
62
dancers (Angioi et al, 2009), years of dancing experience, practise frequency, training
63
intensity (Solomon, Brown, Gerbino & Micheli, 2000; Bruyneel, 2011; Hincapié,
64
Morton & Cassidy, 2008; Shah, 2008), repetitive movements (Macintyre & Joy, 2000;
65
Bruyneel, 2011), inappropriate training prior to bone maturity (Amari et al., 2009), lack
66
of flexibility and range of motion (Macintyre & Joy, 2000) and poor physical fitness
67
levels (Angioi et al., 2009). Moreover, factors such as space, temperature, ventilation
68
and floor type may contribute to musculoskeletal injuries (O’Loughlin, Hodgkins &
69
Kennedy, 2008). However, most of these studies did not correlate the aforementioned
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ACCEPTED MANUSCRIPT aspects with angular measurements of the regions of the body affected by the practise of
71
ballet. Postural assessment may reveal whether participation in ballet induces
72
adaptations and identify which regions of the body are most affected by these
73
adaptations, providing important information for the understanding of injuries that
74
affect the musculoskeletal system of this population.
75
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Thus, the aim of this study was to use photogrammetry to quantitatively evaluate the posture of ballet practitioners and compared to age-matched control
77
Method
78
Participants
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One hundred eleven female volunteers participated in this study and the subjects
80
and their parents signed an informed consent that had been approved by the Ethics
81
Committee on Human Beings under Protocol no. 085-2/2010. The volunteers were
82
divided into two groups: the ballet practising group (n = 52) and the control group (n =
83
59). Volunteers within the ballet practicing group were further divided into three sub-
84
groups according to their years of ballet experience: Group 1, from 1 to 3 years of
85
experience; Group 2, from 4 to 9 years of experience; and Group 3, more than 9 years of
86
experience (Table 1). The control group volunteers were further divided into three age,
87
weight, and height-matched subgroups. Volunteers in the ballet practicing groups
88
participated in two to three 60- to 90-minute ballet classes per week. All dancers
89
belonged to the same vocational institution, had practised dance for at least one year and
90
were at least 7 years old. The control volunteers belonged to two regular schools.
91
Volunteers who were related or had a history of lower limb or spine fracture were
92
excluded from the study. No injury data was collected.
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ACCEPTED MANUSCRIPT Considering the Pelvis Tilt Angle as the main variable, a power effect of 1.00
94
and an effect size of 1.80 (α=0.05) were obtained from a sample size of 111 subjects
95
divided in six groups as described earlier. The GPower® 3.1.7 software (Franz Faut,
96
Universität Kiel Germany, 2008) was used for this analysis (Cohen, 1988, Nakagawa,
97
S.& Cuthill, 2007).
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TABLE 1 TO BE INSERT AROUND HERE
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99 100 Apparatus
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A SONY® Cyber-shot digital camera with a 7.2 megapixel resolution was
103
positioned on a level tripod, parallel to the floor and at a height of one meter, with a
104
distance of 2.4 m between the camera lens and the volunteer (Iunes, Bevilaqua-Grossi,
105
Oliveira, Castro & Salgado, 2009). The volunteer was positioned standing upright, with
106
the upper limbs beside the body and 0.075 m between the medial malleoli. The distance
107
between the medial malleoli was maintained with the aid of ethyl vinyl acetate (EVA)
108
marker. The volunteers were photographed in an anterior view (frontal plane) and a
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right lateral view (sagittal plane).
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For the photographic record of the feet, the camera was positioned on a level
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tripod, parallel to the floor and at a height of 0.45 m, with distance of 0.24 m between
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the camera lens and the podoscope. The digital images were stored and then analysed on
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a personal computer using ALCimagem -2000 Version 1.5 software (Lima, Barauna,
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Sologurem, Canto & Gastaldi, 2004).
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Procedure
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positioned in parallel, and the following anatomical points were marked with an orange
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flexible rod (length = 0.06 m) by the same assessor: the anterior superior iliac spine
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(ASIS); the posterior inferior (PIIS); the spinous processes of T12, L3 and L5; the greater
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trochanter; the fibular head; and the lateral malleolus. The following angles were
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measured: lumbar lordosis (LL), which is formed by the intersection of the direct line
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connecting the T12 spinous process with the L3 spinous process and the direct line
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connecting the L3 spinous process with the L5 spinous process; Pelvic tilt, which is
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formed by the intersection of the direct line connecting the PIIS with the ASIS and the
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horizontal plane (Iunes, Bevilaqua-Grossi, Oliveira, Castro & Salgado, 2009); and knee
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flexion (KF), which is formed by the intersection of the direct line connecting the
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greater trochanter with the fibular head and the direct line connecting the fibular head
129
with the lateral malleolus.
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To take photographs in the frontal plane (Figure 1B), the following anatomical
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points were marked on the skin of the volunteers with white self-adhesive labels: the
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ASIS, the centre of the patella, the tibial tuberosity and the medial malleolus (a flexible
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plastic rod was used for this location). The following angles were measured: Q Angle
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(Smith, Hunt & Donell, 2008) and Knee Angle (KA) (Iunes, Bevilaqua-Grossi, Oliveira,
135
Castro & Salgado, 2009), formed by the intersection of the direct line connecting the
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ASIS with the tibial tuberosity and the vertical plane.
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To take photographs with the lower limbs in external rotation of the hip (Figure
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1C), the following anatomical points were marked: the medial malleolus (orange
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flexible rod), the first metatarsophalangeal joint (1st MTF) (lateral and superior), the
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navicular tuberosity, and 0.06 m below the medial malleolus. The following angles were
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142
drawn along the medial edges of the feet; and the Navicular Angle (NA), which is
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formed by the intersection of the direct line connecting the first MTF (lateral) with the
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navicular tuberosity and the direct line connecting the navicular tuberosity with the
145
marker located 0.06 m below the medial malleolus.
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FIGURE 1 TO BE INSERT AROUND HERE
To take photographs of the forefoot, hindfoot and arch, the participant stood on a
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podoscope with the upper limbs beside the body and the lower limbs separated by an
149
EVA marker (width = 0.075 m). To evaluate the forefoot, the following anatomical
150
points were marked: the heads of the first and fifth metatarsals. To evaluate the
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hindfoot, the following anatomical points were marked: the calcaneal posterior
152
tuberosity (0.03 m above the floor), a second point 0.04 m above the first (i.e., 0.07 m
153
above the floor), a third point at 0.13 m above the floor and a fourth point at 0.22 m
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above the floor, as in Figure 1C. The following angles were measured: Forefoot Angle
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(FA), which is formed by the intersection of the direct line connecting the first
156
metatarsal head with the fifth metatarsal head and the horizontal plane; and Hindfoot
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Angle (HA), which is formed by the intersection of the direct line connecting the first
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point (0.03 m above the floor) with the second point (0.07 m above the floor) and the
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direct line connecting the third point (0.13 m above the floor) and the fourth point (0.22
160
m above the floor), as shown in figure 2. To evaluate the plantar arch (PA), the
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following anatomical points were marked: a straight line was plotted across the mid-
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point of the calcaneus foot print perpendicular to the axis of the foot (A), and a straight
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line was plotted across the isthmus of the plantar arch perpendicular to the axis of the
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foot (B) (Staheli, Chew & Corbett, 1987). PA was defined as the length of B divided by
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the length of A. PA values between 0.01 m and 0.03 m were considered normal. PA
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values greater than 0.01 m were considered flat, and PA values less than 0.03 m were
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considered cavoid (Staheli, Chew & Corbett, 1987). The reliability and validity of measurements by photogrammetry was described
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in previous studies (Ribeiro, Trombini-Souza, Iunes & Monte-Raso, 2006; Iunes,
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Bevilaqua-Grossi, Oliveira, Castro & Salgado, 2009; Iunes, Castro, Salgado, Moura,
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Oliveira & Bevilaqua-Grossi, 2005).
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172 Statistical Analyses
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FIGURE 2 TO BE INSERT AROUND HERE The Kolmogorov-Smirnov (KS) test was used to test the data obtained in this
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study for normality. If the data had a normal distribution, the analysis of variance
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(ANOVA) followed by the Tukey-Kramer tests were performed. In case of non-
178
normality the data, the Kruskal-Wallis followed by the Mann Whitney was used. For all
179
analyses, was considered 5% significance, as calculated using the SPSS v.17.0 software.
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182 183 184
Results
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Analysis: Dancers compared with controls Table 2 shows that when dancers (B1, B2, B3) are compared with their
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respective controls (C1, C2, C3), there was an increase in the angular values of the ER
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of the hip for the dancers in groups B1 and B3 (p <0.01). However, in group B2, the
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angular values of the ER of the hip were similar to those of C2. The LL angle was only
188
increased in dancers in group B2 (p <0.01), while the LL angles of dancers in groups B1
ACCEPTED MANUSCRIPT and B3 were similar to those of their respective controls (C1 and C3). Pelvic tilt was
190
reduced in dancers in group B2 (p <0.01), but the pelvic tilts of dancers in groups B1
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and B3 were similar to those of their respective controls. The positioning of the right
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(FAR, p <0.01) and left (FAL, p <0.01) feet was also reduced in the group B2.
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The other measured variables (i.e., the Knee Angle (RKA and LKA), the Q
194
Angle (RAQ and LAQ), the knee flexion angle (KFA), the forefoot positioning (FAR
195
and FAL), the hindfoot positioning (HAL and HAR) and the plantar arches) were
196
similar among the groups (p >0.05).
TABLE 2 TO BE INSERT AROUND HERE
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Analysis among the dancer groups
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Postural changes in the external rotation (ER), pelvic tilt (Figure 3) and the right
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forefoot (HAR) (Figure 4) were observed in the comparative analysis among the dancer
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groups (p <0.01). There was a difference in the ER angle among the dancer groups
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(Figure 3): ER was increased in B1 and B3 (160.83° and 159.24°, respectively), while
204
ER was decreased in B2 (152.92°). Pelvic tilt was increased (i.e., the pelvis was
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anteverted) in all dancers (Figure 3).
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The angle of the right hindfoot increased steadily among groups B1 (7.65°), B2
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(8.58°) and B3 (11.12°). The results suggest a development of calcaneal valgus over
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time (Figure 4).
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FIGURE 3 TO BE INSERT AROUND HERE
210 211 212
FIGURE 4 TO BE INSERT AROUND HERE
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Discussion This study quantitatively evaluated postural changes in ballet practitioners
215
according to years danced and comparing them to age matched controls. Our hypothesis
216
was that years of ballet experience would promote postural changes in practitioners
217
compared to non-practitioners in different age groups. The results of this study partially
218
support this hypothesis because the postural changes were more consistent between the
219
B2 and C2 groups. The variables that showed differences between these groups
220
(Lumbar Lordosis, Pelvis Tilt, Navicular Right and Left Angles) are very important for
221
postural control and may be associated with musculoskeletal injury. The human body's
222
centre of mass lies in the centre of the pelvis, and the accuracy of its control is essential
223
for accurate classical ballet technique. It was in this region that the main angular
224
changes, especially the reduction of Pelvic Tilt and the increase of the Lumbar Angles
225
(i.e., decreased lumbar lordosis), were identified in group B2. These angular changes
226
reduce the stability of the lumbar segment and may make ballet practitioners prone to
227
injury (Solomon, Brown, Gerbino & Micheli, 2000; Bruyneel, 2011). Low back pain
228
and spine pathologies, such as spondylolisthesis and herniated discs, are commonly
229
reported in dancers. This is because the demands of dance involve extreme and
230
repetitive lumbar hyperextension (Solomon, Brown, Gerbino & Micheli, 2000;
231
Bruyneel, 2011) as well as high impact forces (i.e.big jumps) (Wyon, Twitchett, Angioi,
232
Clarke, Metsios, Koutedakis, 2011). Such problems may arise from repetitive training
233
movements related to dancing, as well as anatomical features and technical errors
234
(Amari et al., 2009).
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Our results reveal that the largest change occurred in the pelvic region, not the
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lumbar region. The positive Pelvic Tilt Angle observed in all volunteers showed the
ACCEPTED MANUSCRIPT presence of anteversion. In group B2, the same angle values were decreased compared
238
to the control group. This change is believed to be related to years of ballet experience
239
because volunteers in B1 and C1 had similar Pelvic Tilt Angles, and their age and BMI
240
characteristics were similar to those of volunteers in B2 and C2. Therefore, the results
241
suggest that the patterns of ballet movements tend to reduce pelvic anteversion, which is
242
characteristic of this age group (Whide, 2001; Giglio & Volpon, 2007) or may have
243
occurred compensation in other joints (Coplan, 2002) which suggests the need for
244
further research.The external rotation of the lower limb in non-dancers becomes fixed
245
between the ages of 8 and 11 years (Benell, Khan, Matthews, Singleton, 2001).
246
However, this rigidity was not observed in ballet practitioners, suggesting a direct
247
influence of training to increase flexibility (Steinberg et al., 2005). External rotation
248
unilateral performed by the hip joint is limited to 70° (Thomasen, 1982). External
249
rotation beyond 70° is obtained by compensation by other regions of the lower limb
250
(Coplan, 2002), such as the tibia, which accounts for 5° of rotation, and the foot, which
251
accounts for 15° of rotation, resulting in a total possible external rotation of 180°
252
bilaterally (Thomasen, 1982). Forced external rotation, which is a serious training error,
253
results in high tensile forces, which, in turn, increase the risk of damage to the posterior
254
region of the knee and other structures of the lower limbs (Ryan & Stephens, 1987;
255
Hald, 1992; Khan et al., 1995; Schon & Weinfeld, 1996;Orishimo, Kremenic, Pappas,
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Hagins & Liederbach, 2009). The literature reports that this is a common error (Ryan &
257
Stephens, 1987; Gilbert, Gross & Klug, 1998). However, when the ballet technique is
258
initiated and practiced at an early age, preventive adaptations in the control of
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movements of the hip in the frontal plane are acquired over the years of practice, and
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can help prevent knee injuries (Orishimo, Kremenic, Pappas, Hagins & Liederbach,
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ACCEPTED MANUSCRIPT 261
2009). Even professional dancers show a limited movement of the hip in the frontal
262
plane which is believed to be derived from higher neuromuscular control and position
263
near the joints. Theories of skeletal maturation in general argue that children have more flexible
265
joints, and with their growth, flexibility and, consequently, movement amplitude are
266
reduced (Moller & Masharawi, 2011; Jansson, 2004). These findings are similar to the
267
results observed in the dancers but not those of the control groups. We believe that as
268
ballet experience increased, dancers began to show soft tissue adaptation ligament
269
flexibility and increased muscle strength (Benell, Khan, Matthews & Singleton, 2001;
270
Duthon,
271
Hoffmeyer. & Menetrey, 2013), similar to female athletes after puberty (Quatman, Ford,
272
Myer, Paterno & Heweet, 2008), or there was compensation in the knee and foot joints
273
(D’Hemecourt & Luke, 2012), which resulted in increased external rotation, as seen in
274
B3. In the present study we used a large age group which was originally the variability
275
of years of ballet practice in groups. Thus it is believed that these skills may also be
276
influenced by the different times of musculoskeletal maturation. However, other factors
277
could contribute to increased flexibility, such as genetic changes (eg presence of
278
ACTN3 XX genotype) (Kim, Jung, Ki, Youn & Kim, 2014). These factors should also
279
be considered when interpreting the results presented in the different groups, due to the
280
fact that these characteristics were not evaluated in this study.The Navicular Angle of
281
both feet was lower in the dancer groups than in the control groups. This difference was
282
particularly apparent in the left foot. These findings suggest that the practise of ballet is
283
associated with a strengthening of the intrinsic foot muscles (Mulligan & Cook, 2013)
284
(Table 1), but these data would be more notable if the increase or change in the arch
Kolo,
Magnenat-Thalmann,
Becker,
Bouvet,
Coppens,
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ACCEPTED MANUSCRIPT correlated to years of ballet experience, which was not observed. We believe that this
286
adaptation may be related to the use of pointe shoes, which contributes to the
287
maintenance of an isometric contraction of the intrinsic muscles during some postures
288
(Mulligan & Cook, 2013), as well as increased strength of the posterior tibial muscle.
289
However, training to increase the flexibility of the joints in the forefoot may increase the
290
local amplitude and consequently decrease the plantar arch, thus counteracting the
291
findings in the Foot Angle.
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The static analysis presented here can be considered a limitation of this study. In
293
dynamic conditions, the nervous system can find alternate ways to perform movements
294
(Latash, 2012), thus minimizing the impact of the pelvic differences observed in this
295
study. However, the aim of this study was to quantify the influence of years of ballet
296
experience on the practitioner's posture.
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The limitations of the study is the lack of control of outside activities amongst
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the dancers as well as the large variation in age in our cohort. Additionally the dancers
299
are considered recreational rather than elite level.
300 301
Conclusion
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Research shows there are significant differences between dancers and controls.
303
In the groups 1 to 3 years and more than 9 years of ballet experience, the External
304
Rotation Angle is greater in the dancers. In the group 4 to 9 years of ballet experience
305
the Lumbar Lordosis Angle is greater and Pelvis Tilt, Navicular Angle Left and Right
306
are smaller in the dancers. In more to 9 years of ballet experience, the Navicular Angle
307
Left is smaller.
308
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ACCEPTED MANUSCRIPT 309 310 311
Conflict of interest The authors state that there are no conflicts of interest that might have influenced the preparation of this manuscript.
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ACCEPTED MANUSCRIPT Table 1. Mean values (95 % CI) of sample characteristics Groups (n) B1 (9) Age
B2 (21) B3 (22) B1 (9)
BMI
B2 (21) B3 (22)
Body
Groups (n)
Control (n=59) 11.00 (8.74 – 11.91)
C1 (9)
11.22
C2 (22) C3 (28) C1 (9) C2 (22)
17.14 (15.88 – 18.73) 18.01 (14.91 – 19.42) 17.37 (16.84 – 19.64) 20.03 (18.42 – 20.46)
C3 (28)
mass
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Ballet (n=52) 11.22 (8.66 – 13.55) 11.55 (9.66 – 12.43) 17.73 (16.56 – 19.26) 19.44 (16.90 – 21.98) 17.52 (16.72 – 18.30) 20.72 (19.91 – 21.52)
p 0.590 0.805
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0.906 0.063
0.190 0.139
index;
ACCEPTED MANUSCRIPT 430 431 432 433
Table 2. Postural analysis between dancers and non-dancers; mean values (95%CI). B1 = 1 to 3 years of ballet experience; B2 = 4 to 9 years of ballet experience; B3 = more than 9 years of ballet experience; C1 = control group 1; C2 = control group 2; C3 = control group 3.
434
Control Pelvis Tilt Anglea Ballet Control Q Angle Righta Ballet Control Q Angle Leftb Ballet Control
External Rotation Angleb
Ballet
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Control Knee Angle Righta
Ballet
Control Knee Angle Leftb
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Control
Flexion Knee Angleb
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Ballet
Navicular Angle Righta
Navicular Angle Lefta
Forefoot Angle Righta
Control Ballet
Control Ballet
Control Ballet Control
Forefoot Angle Lefta Ballet
C3 vsB3 (o) 158.33 (155.41-161.25) 158.49 (154.95-162.03) 10.14 (7.63-12.65) 13.17 (10.74-15.60) 17.6 (15.01-20.20) 17.66 (15.22-20.08) 15.41 (12.62-18.19) 17.92 (15.70-20.13) 151.00* (146.58-155.42) 159.24 (156.73-161.75) 175.23 (174.70-175.77) 175.57 (174.78-176.36) 175.58 (174.73-176.44) 176.50 (175.85-177.14) 182.40 (180.33-184.48) 185.02 (182.88-187.16) 133.32 (125.88-140.77) 121.47 (113.31-131.22) 139.23* (132.43-146.03) 119.73 (110.39-129.24) 7.07 (6.01-8.12) 7.65 (6.67-8.61) 6.49 (5.47-7.50) 8.47 (7.40-9.54)
F (3,107)
RI PT
Ballet
C2 vsB2 (o) 151.22* (146.83-155.60) 159.86 (156.66-163.06) 15.66* (12.33-18.99) 8.41 (5.68-11.12) 18.09 (14.97-21.19) 18.35 (15.47-21.22) 16.78 (14.06-19.49) 18.67 (15.64-20.69) 153.01 (149.33-156.70) 152.92 (150.19-155.64) 175.21 (174.52-175.89) 175.50 (174.78-176.42) 176.09 (174.84-177.34) 176.22 (176.48-176.95) 181.83 (179.26-184.41) 182.40 (179.54-185.26) 140.83* (135.78-145.88) 125.39 (119.68-131.11) 143.72* (134.65-152.79) 124.04 (116.81-132.27) 8.27 (6.78-9.74) 8.74 (7.12-10.34) 7.66 (6.40-8.91) 6.85 (5.90-7.80)
SC
Control
Lumbar Lordosis Anglea
C1 vsB1 (o) 155.26 (148.17-162.35) 154.77 (151.10-158.44) 8.71 (5.72-11.65) 11.29 (7.47-15.11) 12.53 (8.53-16.52) 16.68 (12.42-21.93) 11.07 (6.62-15.50) 16.55 (13.01-20.07) 142.64* (131.55-153.74) 160.83 (154.11-167.56) 176.67 (175.02-178.32) 175.14 (173.89-176.39) 175.97 (174.16-177.79) 175.50 (174.19-176.80) 179.04 (174.84-183.24) 183.95 (179.10-188.81) 138.40 (128.13-148.67) 115.92 (99.59-132.25) 136.34 (126.84-145.84) 118.76 (111.43-126.09) 9.04 (7.53-10.55) 7.72 (6.50-8.93) 8.03 (5.54-10.62) 7.97 (6.16-9.77)
M AN U
Angles
p
3.363c
0.007
4.092c
0.002
0.753
0.586
-----
0.024
-----
0.000
0.638
0.671
-----
0.3377
-----
0.097
5.030c
0.000
6.431
0.000
1.400
0.287
1,810
0.102
ACCEPTED MANUSCRIPT
Ballet Control Ballet
Measures Arch of the foot Rightb
Arch of the foot Leftb a
436
F Value: 2.698
Ballet Control Ballet
8.95 (7.39-10.49) 8.58 (7.06-10.10) 9.78 (8.22-11.27) 7.71 (6.33-9.09) B2/C2 (cm) 0.30 (0.18-0.41) 0.34 (0.20-0.46) 0.24 (0.10-0.36) 0.40 (0.25-0.53)
8.98 (7.53-10.42) 11.12 (9.61-12.61) 8.97 (7.86-10.03) 6.69 (5.25-8.13) B3/C3 (cm) 0.31 (0.21-0.40) 0.34 (0.23-0.44) 0.36 (0.24-0.46) 0.34 (0.23-0.44)
1.959
0.104
3.553
0.005
AC C
EP
TE D
437 438
p
-----
0.855
-----
0.254
– ANOVA Test; b – Kruskal Wallis Test;* - control versus Ballet- pos hoc test. cCritical
M AN U
435
Control
9.90 (7.28-12.51) 7.65 (4.71-10.59) 10.21 (8.19-12.19) 9.50 (6.27-12.72) B1/C1 (cm) 0.35 (0.17-0.53) 0.44 (0.25-0.61) 0.36 (0.18-0.54) 0.52 (0.28-0.75)
RI PT
Hindfoot Angle Lefta
Control
SC
Hindfoot Angle Righta
SC
RI PT
ACCEPTED MANUSCRIPT
M AN U
439
Figure 1. The angles evaluated in the photographs. Feet were maintained in parallel in
441
(A) and (B) and in external rotation in (C). PT = Pelvic Tilt; LL = Lumbar Lordosis; KF
442
= Knee Flexion; Q = Q Angle; KA = Knee Angle; ER = External Rotation; NA = Foot
443
Angle.
EP AC C
444
TE D
440
ACCEPTED MANUSCRIPT
M AN U
SC
RI PT
445
446
Figure 2. 1A, forefoot marker points; 1B, hindfoot marker points; 1C, plantar arch
448
analysis (FA = Forefoot Angle; HA = Hindfoot Angle).
EP
450
AC C
449
TE D
447
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
451
Figure 3. Postural analysis (lumbar lordosis, angle of pelvic tilt, external rotation and
453
flexion knee angle) between dancers with varying years of ballet experience. B1 = 1 to
454
3 years of ballet experience; B2 = 4 to 9 years of ballet experience; B3 = more than 9
455
years of ballet experience.
AC C
EP
TE D
452
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
TE D
456
Figure 4. Postural analysis (Knee Angle, Hindfoot Angle, Foot Angle, Arch of the foot)
458
between dancers with varying years of ballet experience. B1 = 1 to 3 years of ballet
459
experience; B2 = 4 to 9 years of ballet experience; B3 = more than 9 years of ballet
460
experience.
AC C
461
EP
457
ACCEPTED MANUSCRIPT Acknowledgements The authors would like to thank the Adagio Ballet Company, Sagrado Coração de Jesus School and CAZITA for allowing the volunteers’ participation. We would also like to thank the Federal University of Alfenas and The National
RI PT
Council for Scientific and Technological Development (CNPq) for their financial
AC C
EP
TE D
M AN U
SC
assistance.
ACCEPTED MANUSCRIPT Highlights
2. 3.
The posture of the dancers changes between four and nine years of ballet practice. Pelvic tilt is reduced in the group of dancers compared to a control group. Lumbar lordosis is reduced in the group of dancers compared to a
RI PT
1.
AC C
EP
TE D
M AN U
SC
control group.