The effect of Demi Plié in ballet on children with spastic cerebral palsy：A cross-sectional observational study

The effect of Demi Plié in ballet on children with spastic cerebral palsy：A cross-sectional observational study | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article The effect of Demi Plié in ballet on children with spastic cerebral palsy：A cross-sectional observational study Jie Ren, Chunxin Xu, Yangyang Lu, Cen Chen, Shenyu Zhu, Min Shen This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7410912/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background Demi Plié is the most basic movement in classical ballet. Previous studies have shown that Demi Plié may be beneficial for maintaining the posture of patients with cerebral palsy. However, studies also reported that Demi Plié caused injury. The aim of this study was to observe the angles and moments of the lower limb joints of cerebral palsy at different foot turn-out angle of Demi Plié. Methods A cross-sectional observational study was conducted and divided into two group. Joint angles and moments were collected during Demi Plié at progressive foot turn-out angles (30°, 60°, 90° and 120°). Results With the increase of foot turn-out angles, the external rotation and eversion angles of the ankle increased( P < 0.001), and the eversion moments of ankle increased while the external rotation moments of ankle decreased( P ≤ 0.001). The external rotation angles of tibia increased with increasing turn-out angles ( P < 0.001). The extension moments of knee in cerebral palsy group was less than that in the typically developing group ( P = 0.021). Hip abduction angles and hip external rotation angles in both groups increased with the increase of turn-out angles( P < 0.001), while hip extension moments and hip abduction moments decreased( P < 0.05). Pelvis rotation angles were greater in cerebral palsy group compared to typically developing group. Conclusions A large turn-out angle (90° or 120°) may cause excessive stress to lower limb joints, leading to injury in cerebral palsy patients, especially those who have a crouching gait with hyperflexion of the knee and hip and deformities associated with ankle eversion. Trial Registration The trial was registered with the full protocol accessible through Chinese Clinical Trial Registry (ChiCTR) website(https//www.chictr.org.cn/) on February 23rd, 2021. Trial registration number ChiCTR2100043593. Dance therapy Ballet Cerebral palsy Three-dimensional motion Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 1 INTRODUCTION Cerebral palsy (CP) is a neurological disorder that affects movement, posture, and balance and is accompanied by sensory, perceptual, cognitive, communication and behavior disorders[ 1 ]. The primary neurological impairment affects muscle tone and secondary leads to joint contractures and bone deformities, such as equinus, stiff knee and torsional syndromes, causing lever arm dysfunction (LAD). The common LAD in the CP is torsion deformity in the horizontal plane, including femoral internal rotation and tibial internal rotation, and tibial internal rotation is more common than femoral internal rotation [ 2 – 3 ]. Torsion deformities of the lower limb are also associated with deformities associated with hip flexion, knee flexion and ankle eversion [ 4 ]. Femoral internal rotation reduces the lever arm of the hip abduction, resulting in an inability to produce hip abduction moments even if the hip abductor muscle strength is sufficient. Tibial torsion shortens the lever arm of ankle plantar flexion and knee extension, further exacerbating gait problems such as crouching [ 5 ]. Dance therapy, such as ballet therapy, is a promising therapeutic method for children with CP[ 6 – 8 ]. Demi Plié is the most basic movement in classical ballet. The Demi Plié movement requires keeping the torso upright while flexing the hip and knee, rotating externally, and dorsiflexing the ankle. Studies have shown that Demi Plié can activate the triceps calf, gluteus maximus, and gluteus medius, which may be beneficial for maintaining the posture of the CP [ 9 ]. However, studies have reported that maintaining a large foot turn-out angle could cause medial misalignment of the knee relative to the ipsilateral foot, which can result in the accumulation of tension on the medial collateral ligament and serve as a predisposing factor for future injury [ 10 ]. External hip rotation is used to compensate for the tension on the ankle and knee to achieve the maximum foot turn-out angle and potentially exaggerate the anterior pelvic tilt [ 11 ]. Some researchers believe that aligning the foot with the center of the knee is preferable and less damaging [ 12 ]. Owing to the gait pattern of the CP, it was difficult for them to achieve the standard turn-out angle of the foot and hip during Demi Plié. The effects of Demi Plié on CP have not been previously reported. The aim of this study was to observe the angles and moments of the lower limb joints of the CP at different foot turn-out angles of Demi Plié (FADP) and to determine whether Demi Plié may injure the CP and how to avoid it. 2 METHODS The trial and the statistical analysis plan were registered On February 23rd, 2021 at the Chinese Clinical Trial Registry (ChiCTR2100043593). The trial was approved by the Medical Ethics Committee of Shanghai Rehabilitation Institute for the Exceptional Children (China, Shanghai) (2020-072). The trial was an observational cross-sectional study and was conducted in accordance with the requirements of the STROBE Statement. Children aged 16 and below who participated in this experiment have obtained the informed consent of their parents or legal guardians. 2.1 Participants All measurements were performed in the gait analysis laboratory, at the Shanghai Rehabilitation Institute for the Exceptional Children, in Shanghai, China between from November 2021 to November 2022. Participants were recruited through advertisements, and all the subjects who met the eligibility criteria were invited by telephone. The CP group consisted of children aged 4 to 16 years with Gross Motor Function Classification System (GMFCS) grades I to II and no surgical history or botox injections within the past 6 months. The typically developing (TD) group included children from nearby communities. All the children were in good health, and both they and their parents voluntarily participated in this study. Those with severe cognitive and mental dysfunction and other serious systemic organic diseases (e.g., heart, liver, kidney and endocrine and metabolic disorders) were excluded. Data were excluded for children who were unable to complete the study as needed. In total, 20 children were included in each group for a total of 40 children for analysis. 2.2 Maker arrangement and demi plié movement Markers were placed on each subject according to the modified conventional gait model[ 13 ]. The following locations were marked: left and right posterior superior iliac spine, left and right anterosuperior iliac spine, left and right lateral thigh (marked with wand), left and right later shank (marked with wand), left and right tibial plateau (not included in the modified conventional gait model market set), left and right medial and lateral epicondyle of the femur, left and right medial and lateral malleolus, left and right 1st, 2nd and 5th metatarsal head and base, and left and right dome of the calcaneus (Fig .1). Demi Plié movement does in the second foot position of ballet: two heels on the ground in a straight line, toes turn out, feet one foot apart, and children perform a half squat movement, ensuring that their knee does not exceed the toe. According to classical ballet standards, the turn-out angle of the foot should be close to 180°, but this approach could be difficult for CP children. Previous studies have reported that this angle may cause injury to the lower limb joints [ 10 ]. To address this, four progressive angles of the foot were chosen: 30°, 60°, 90°, and 120°. Fig .1 Maker arrangement in the front and direction of virtual coordinate system construction. 2.3 Data collection Three-dimensional motion capture was performed via a twenty-camera motion tracking system (Motion Analysis Corp., Santa Rosa, CA), with twelve cameras on the ceiling and eight on the ground. The tracking system captured data at a frequency of 120 Hz. Biomechanical data were collected from the force platform (Bertec Corp., Worthington, British) at 1000 Hz. Cortices 2.2.1 were used to track the marker trajectories. The data collection process involved the following steps: first, the personal information (gender, age, BMI, GMFCS level and classification) was collected; then, a physical assessment (lower extremity passive joint angles and muscle tension test) was performed. In physical assessment, the popliteal angle measures the tension of the hamstring muscle, the thigh-foot angle (TFA) and transmalleolar axis (TMA) measure the torsional angle of the tibia, and the Q angle measures the knee valgus angle by measuring the angle between the line of the tibial tubercle and the long axis of the thigh. The subjects were brought to the lab, and data were collected as they performed Demi Plié movements at 30°, 60°, 90° and 120° of foot turn out. Because biomechanical data could not be obtained when the two feet were on the same force plate at the same time, data were captured for 3 instances with one side of the subject contacting the force plate at a time and then the other. Each turn was maintained for 10 s, followed by a rest period of 30 s. Two therapies were arranged to help the subjects complete the required movements. In the Cortex software, marker points were named, and a .c3d file was created and imported into Visual 3D (C-Motion, Inc., Germantown, MD). A virtual coordinate system was created in visual 3D, and the X, Y and Z axes of the virtual coordinate system represent the motion of the lower limb joints in the sagittal plane (extension/flexion), the coronal plane (inversion/eversion, adduction/abduction, varus/valgus) and the horizontal plane (internal/external rotation). The segments are defined by target markers at the proximal and distal joints. For example, the right thigh region was defined as follows: At the proximal (upper) end of the right thigh, the position of the right hip marker is used together to define the proximal endpoint. At the distal end, both medial and lateral knee markers are available and together define both the distal endpoint and the distal radius of the thigh segment. Any two segments in proximity to be "linked" and references a Joint. Angles and moments of the lower limb joint were processed via visual 3D. 2.4 Statistical analysis Statistical analysis was performed via SPSS version 25.0 (Property of IBM Corp, New York, America). An alpha level of 0.05 was used to determine significance. Missing data were not included in the analysis. The significant differences in baseline parameters between the two groups were determined via the independent sample t test or Mann‒Whitney U test. Since the main parameters (joint angles and moments) at the progressive FADP (30°, 60°, 90°, 120°) were collected by the same subject each time, the intragroup data did not meet the condition of mutual independence. Therefore, a repeated-measures ANOVA was used as a priority, and a sphericity test was conducted to confirm the correlation between the data. 3 RESULTS 3.1 Clinical characteristics for each group Twenty children with CP and twenty TD children (aged 4–16 years) completed the test. In each group, the proportions of males and females were equal (28 males and 12 females). The proportions of patients with GMFCSs Ⅰ and Ⅱ in the CP group were the same (GMFCS I:GMFCS II = 10:10) and included both unilateral and bilateral involvement, with 65% being hemiplegic in the CP group. There were no intergroup differences in BMI values ( P = 0.156) (Table 1 ). Table 1 Participant characteristics Characteristic CP (n = 20) TD (n = 20) P value Age, y 7.80 ± 3.0 11.75 ± 4.4 < 0.001 Sex, male/female 14/6 14/6 1.000 BMI, kg/m 2 17.47 ± 3.02 18.79 ± 2.74 0.156 GMFCS LevelⅠ/Ⅱ, n 10/10 - - Unilateral/bilateral, n 13/7 - - Physical assessment revealed significant differences between the two groups in hip abduction, ankle dorsiflexion with knee extension/flexion, ankle plantar flexion, torsion angle of the tibia (TFA, TMA) and the Q angle ( P < 0.05) (Table 2 ). Compared with the TD group, the children in the CP group had limited angles of hip abduction, ankle plantar flexion and dorsiflexion but more tibial internal rotation. Popliteal angle, Ely and Thomas tests were significantly different between the two groups ( P < 0.05), indicating that CP individuals had greater hamstring tension, iliopsoas tension and quadriceps tension and that these muscles play important roles in maintaining the stability of the lower limb chain (pelvic, hip, knee and ankle) [ 4 , 14 – 16 ]. Table 2 Comparison of the physical assessment data between the two groups CP(mean and 95% CI) TD (mean and 95% CI) Z/x 2 value P value Hip flexion ROM 135.0(126.2 ~ 138.0) 135.0(133.50 ~ 140.0) -1.70 0.089 Hip extension ROM 11.0(10.0 ~ 12.76) 12.00(11.00 ~ 13.00) -1.383 0.167 Hip internal rotation ROM 70.0(79.50 ~ 65.5) 67.00(61.25 ~ 75.00) -1.693 0.091 Hip external rotation ROM 40.0(37.25 ~ 49.75) 45.00(40.00 ~ 54.00) -1.861 0.063 Hip abduction ROM 51.5(44.00 ~ 58.00) 54.00(50.00 ~ 60.00) -2.031 0.042* Knee flexion ROM 150.0(144.0 ~ 152.0) 149.00(140.00 ~ 153.00) -0.540 0.589 Knee extension ROM 1.00(0.00 ~ 2.00) 0.00(0.00 ~ 3.00) -0.384 0.701 Popliteal angle 40.00(37.00 ~ 53.75) 35.00(30.00 ~ 38.75) -4.564 < 0 .001* Ankle dorsiflexion ROM (Knee ext) 5.50(-2.50 ~ 10.00) 10.00(4.25 ~ 15.00) -3.109 0.002* Ankle dorsiflexion ROM (Knee flexn) 19.00(10.00 ~ 21.75) 20.00(15.00 ~ 28.00) -2.388 0.017* Ankle plantar flexion ROM 32.00(28.50 ~ 37.00) 35.50(32.00 ~ 40.00) -2.318 0.020* TFA -8.50(-11.75~-5.00) -14.50(-18.75~-10.00) -4.552 < 0 .001** TMA -9.50(-15.00~-5.00) -15.50(-20.00~-11.00) -3.828 < 0 .001** Q angle -2.00(-3.00~-2.00) -3.00(-4.00~-2.00) -2.323 0.020* Ely test(Rectus femoris muscle tension test) + - 5.165 0.023* Thomas test(Iliopsoas muscle tension test) + - 11.429 0.001* Note : The inverted/varus/adduction angles are positive, and the eversion/valgus/abduction angles are negative. * P < 0.05; ** P < 0.001. TFA, Thighfoot angle. TMA, transmalleolar axis. 3.2 Ankle parameters Ankle parameters (as shown in Fig. 2 ) revealed that there was a significant effect of FADP in the ankle angles on the X‒Y‒Z axes (sagittal, coronal, and horizontal planes) (intragroup differences, P < 0.001). The external rotation and eversion angles of the ankle increased with increasing FADP. There was a significant effect of FADP on ankle moments on the Y-axis and Z-axis (coronal and horizontal planes) (intragroup differences P ≤ 0.001). The external rotation moment of the angle decreased with increasing FADP and then became an internal rotation moment at 120° of the FADP. The eversion moment of the ankle increased with increasing FADP, which was greater in the TD group than in the CP group. 3.3 Knee parameters Knee parameters (Fig. 3 ) revealed that there was a significant effect of FADP (intragroup differences P < 0 .001) on the knee angle on the Z-axis (horizontal plane). The external rotation angle of the tibia increased with increasing FADP. The extension moment of the knee on the X-axis (sagittal plane) in the CP group was less than that in the TD group (intergroup difference P = 0.021). Although there was no intragroup or intergroup difference in the knee moment on the Z-axis (horizontal plane), both groups tended to increase the internal rotation moment after 60° of FADP. 3.4 Hip parameters Hip parameters (Fig. 4 ) revealed a significant effect of FADP (intragroup P < 0.001) on hip angles on the Y-axis and Z-axis (coronal and horizontal planes). The hip abduction angle and hip external rotation angle increased with increasing FADP in both groups. There were also intergroup ( P < 0.050) differences; the hip abduction angle was greater in the CP group than in the TD group, whereas the hip external rotation angle in the CP group was less than that in the TD group. There was a significant effect of FADP on hip moments on the X-axis (sagittal plane) (intragroup P = 0.044) and on hip moments on the Y-axis (coronal plane) (intragroup P < 0 .001). With increasing FADP, both groups generated hip flexion moments at 90° or 120° of the FADP. The hip abduction moment decreased in both groups until the adduction moment was reached in the CP group at 120° FADP, and the hip abduction moment was greater in the TD group than in the CP group (intergroup P = 0.001). 3.5 Pelvic parameters Pelvic parameters (Fig. 5 ) revealed significant intergroup differences ( P = 0.001) in the pelvis angle between the two groups in the Z-axis (horizontal plane), and the rotation of the pelvis angle (absolute rotation deviation) in the horizontal plane in the CP group was greater than that in the TD group. 4 DISCUSSION This study aimed to observe the angles and moments of the lower limb joints of the CP at different foot turn-out angles of Demi Plié and to determine whether Demi Plié may injure the CP and how to avoid it. The results preliminarily showed that the large angle of FADP, such as 90° or 120° of Demi Plié movement in ballet training, may cause excessive stress to the joint and lead to injury to the CP. The results of the ankle data revealed that after 30° of FADP, the ankle dorsiflexion angles and plantar flexion moments in the CP group decreased gradually with increasing FADP, and the ankle eversion angles and eversion moments increased in both groups. This means that the increasing angles of FADP may aggravate the LAD problem of valgus deformities such as pes planus in the CP. These results have also been reported in previous studies on ballet dancers, which indicate that to maintain a larger FADP, the arch of the foot drops, and the foot tends to pronate[ 17 ], which further leads to injury of the medial meniscus and medial collateral ligament of the knee with an increasing tendency toward knee valgus[ 10 ]. The results of the knee data revealed that an increase in the FADP led to greater external rotation of the tibia in both groups. This finding indicated that Demi Plié may be beneficial for improving the external rotation angle of the tibia in the CP, according to the physical assessment results: the CP had more tibial internal rotation than did the TD. However, the knee extension moment in the CP group was significantly smaller than that in the TD group, indicating that the strength of the knee extensors in the CP group during Demi Plié was still weaker than that in the TD group. This may be due to the greater degree of knee flexion in the CP group due to the weakness of the knee extensors (Fig. 3 ), which may further exacerbate LAD problems in CP individuals who have a crouching gait characterized by flexion deformities of the knee and hip. The results of the hip data revealed that with increasing FADP, the hip abduction angle and hip external rotation angle increased in both groups. The hip abduction angle in the CP group was larger than that in the TD group, whereas the abduction moment was smaller than that in the TD group. The intergroup difference in the abductor moment suggested that the strength of the hip abductor muscle group in the CP was relatively weak, and to maintain balance, the CP seems to compensate by increasing the angle of hip abduction and external rotation and widening the distance between their feet. In Fig. 4 , at 30°, 60° and 90° of FADP, the line of hip abduction moment data of the CP group was above the critical boundary (≥ 0), indicating that the hip abductor muscle was active during Demi Plié and may be helpful for the CP. However, it is important to note that a large angle of FADP may be unfavorable for CP individuals. The hip adduction moment was generated in the CP group at 120° of FADP, and the hip flexion moment was generated in both groups at 90° of FADP. Combined with the data of the pelvis shown in Fig. 5 , we found that with increasing FADP, the angles of the pelvis in the horizontal plane and coronal plane increased in the CP group. On the basis of these observational results, we speculate that increasing the FADP angle may lead to increased hip flexion compensation and pelvic instability in the CP. 5 CONCLUSION In conclusion, the Demi Plié movement in ballet training for CP children needs to be regulated. A large FADP angle, such as 90° or 120°, may cause excessive stress on the joint and lead to injury to the CP, especially those who have a crouching gait with hyperflexion of the knee and hip and deformity of the pes planus (ankle eversion).However, further investigations of the long-term effects of the Demi Plié movement on the CP are needed to confirm these conclusions. This is the first study to explore the effect of the Demi Plié movement on children with CP. However, as an advanced observational study, this study has several limitations. For example, only immediate data were collected during a trial, and the generalizability of the study results is limited. In addition, only CP children with GMFCS grades Ⅰ-Ⅱ were included for observation and analysis in the trial because of the difficulty of performing the Demi Plié movement for children with high motor dysfunction. Although not all types of CP were included in this study, the results are beneficial for CP who practice dance, especially ballet dance, to avoid possible injury and help develop appropriate dance training plans. Abbreviations CP Cerebral palsy FADP Foot turn-out angle of Demi Plié LAD Lever arm dysfunction TD Typically, developing group TFA Thigh-foot angle TMA Transmalleolar axis Declarations Acknowledgments This study has been inspired by Professor Deborah Gaebler Spira, who has given us a lot of guidance during research. Author Contributions Jie Ren wrote the original manuscript. Chunxin Xu was responsible for supervising the project and the final review. Yangyang Lu analyzed the data. Cen Chen and Shenyu Zhu participated in the clinical investigation. Min Shen was responsible for the entire project. Funding Not applicable. Data availability Data is provided within the manuscript or supplementary information files. Ethics approval and consent to participate This study was approved by the Medical Ethics Committee of Shanghai Rehabilitation Institute for the Exceptional Children (China, Shanghai) (2020-072). Children aged 16 and below who participated in this experiment have obtained the informed consent of their parents or legal guardians. The study was conducted in accordance with the Declaration of Helsinki (https://www.wma.net/policies-post/wma-declaration-of-helsinki/). Consent for publication Consent for publication has been obtained from children or their parent or legal guardian. Competing interests The authors declare that they have no competing interests. References Wimalasundera N, Stevenson VL. Cerebral palsy. Pract Neurol. 2016;16(3):184–94. 10.1136/practneurol-2015-001184 . Rethlefsen SA, Kay RM. Transverse plane gait problems in children with cerebral palsy. J Pediatr Orthop. 2013;33(4):422–30. 10.1097/BPO.0b013e3182784e16 . Gaston MS, Rutz E, Dreher T, Brunner R. Transverse plane rotation of the foot and transverse hip and pelvic kinematics in diplegic cerebral palsy. Gait Posture. 2011;34(2):218–21. 10.1016/j.gaitpost.2011.05.001 . Chong KC, Vojnic CD, Quanbury AO, Letts RM. The assessment of the internal rotation gait in cerebral palsy: an electromyographic gait analysis. Clin Orthop Relat Res. 1978;(132):145–50. Theologis T. Lever arm dysfunction in cerebral palsy gait. J Child Orthop. 2013;7(5):379–82. 10.1007/s11832-013-0510-y . 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J Pediatr Orthop. 2004;24(3):278–82. 10.1097/00004694-200405000-00008 . Lofterød B, Terjesen T. Changes in lower limb rotation after soft tissue surgery in spastic diplegia. Acta Orthop. 2010;81(2):245–9. 10.3109/17453671003587135 . Khan K, Brown J, Way S, et al. Overuse injuries in classical ballet. Sports Med. 1995;19(5):341–57. 10.2165/00007256-199519050-00004 . Additional Declarations No competing interests reported. Supplementary Files supplementarydatafile.docx Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7410912","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":527178478,"identity":"f8c6794a-cee6-4962-9403-b49385df36f7","order_by":0,"name":"Jie Ren","email":"","orcid":"","institution":"Shanghai Rehabilitation Institute for the Exceptional Children","correspondingAuthor":false,"prefix":"","firstName":"Jie","middleName":"","lastName":"Ren","suffix":""},{"id":527178481,"identity":"fc8b7e9e-075e-4e06-ad3d-93d88fb8f284","order_by":1,"name":"Chunxin Xu","email":"","orcid":"","institution":"Shanghai Rehabilitation Institute for the 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17:38:17","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7410912/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7410912/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":93339371,"identity":"fb99e92d-8f3e-4543-8bd1-689487bf8c26","added_by":"auto","created_at":"2025-10-12 14:25:39","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":1109019,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript2025.September.docx","url":"https://assets-eu.researchsquare.com/files/rs-7410912/v1/b727493db614d897f64f346c.docx"},{"id":93339359,"identity":"21e6666c-89ca-44d3-944b-b8e8a85a2b7c","added_by":"auto","created_at":"2025-10-12 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14:25:39","extension":"html","order_by":15,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":81057,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7410912/v1/6719c265cef785526624726c.html"},{"id":93340699,"identity":"dbc1f077-4ea4-4d3b-a44a-c15b50e2a91b","added_by":"auto","created_at":"2025-10-12 14:33:39","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":309960,"visible":true,"origin":"","legend":"\u003cp\u003eMaker arrangement in the front and direction of virtual coordinate system construction.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-7410912/v1/c5ed51575db99c98d5e5eecd.png"},{"id":93339360,"identity":"8029b5d0-85a9-4cfc-86a2-ac255da06c4c","added_by":"auto","created_at":"2025-10-12 14:25:39","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":193898,"visible":true,"origin":"","legend":"\u003cp\u003eBroken line graph of the ankle angles and moments on the X-Y-Z axis with increasing FADP.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e(a)(b)\u003c/strong\u003eX-axis: The signs of the dorsiflexion angle and plantar flexion moment are positive, and the plantarflexion angle and dorsiflexion moment are negative. \u003cstrong\u003e(c)(d)\u003c/strong\u003eY-axis: The signs of the ankle eversion angle and inversion moment are positive, and the ankle inversion angle and eversion moment are negative.\u003cstrong\u003e (e)(f)\u003c/strong\u003eZ-axis: The signs of the internal rotation angle and external rotation moment are positive, and the external rotation angle and internal moment are negative.\u003c/p\u003e\n\u003cp\u003e* intragroup \u003cem\u003eP\u003c/em\u003e\u0026lt; 0.05 ** intragroup \u003cem\u003eP\u003c/em\u003e\u0026lt;0 .001, \u003csup\u003e#\u003c/sup\u003e indicates intergroup \u003cem\u003eP\u003c/em\u003e\u0026lt;0.05\u003c/p\u003e","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7410912/v1/7cd2c43bd9f803d220f37a9e.jpeg"},{"id":93339363,"identity":"6adb4ec3-3484-4a3d-a717-ab2d42767b85","added_by":"auto","created_at":"2025-10-12 14:25:39","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":218506,"visible":true,"origin":"","legend":"\u003cp\u003eBroken line graph of the knee angles and moments on the X-Y-Z axis with increasing FADP.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e(a)(b)\u003c/strong\u003eX-axis: The signs of the flexion angle and extension moment are positive, and the extension angle and flexion moment are negative. \u003cstrong\u003e(c)(d)\u003c/strong\u003eY-axis: The knee varus angle and valgus moment are positive, and the knee valgus angle and varus moment are negative. \u003cstrong\u003e(e)(f)\u003c/strong\u003eZ-axis: the internal rotation angle and external rotation moment are positive, and the external rotation angle and internal moment are negative.\u003c/p\u003e","description":"","filename":"floatimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7410912/v1/79f76ea43f9e952536482267.jpeg"},{"id":93340703,"identity":"74b05c0c-a5f8-4cc1-9815-a54b2b2a32c7","added_by":"auto","created_at":"2025-10-12 14:33:39","extension":"jpeg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":204735,"visible":true,"origin":"","legend":"\u003cp\u003eBroken line graph of the hip angles and moments on the X-Y-Z axis with increasing FADP.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e(a)(b)\u003c/strong\u003eX-axis: The signs of the flexion angle and extension moment are positive, and the extension angle and flexion moment are negative. \u003cstrong\u003e(c)(d)\u003c/strong\u003eY-axis: the signs of the hip adduction angle and abduction moment are positive, and the abduction angle and adduction moment are negative. \u003cstrong\u003e(e)(f)\u003c/strong\u003eZ-axis: The signs of the internal rotation angle and external rotation moment are positive, and the external rotation angle and internal moment are negative.\u003c/p\u003e\n\u003cp\u003e* intragroup \u003cem\u003eP\u003c/em\u003e\u0026lt; 0.05 ** intragroup \u003cem\u003eP\u003c/em\u003e\u0026lt; 0.001, \u003csup\u003e# \u003c/sup\u003eintergroup \u003cem\u003eP\u003c/em\u003e\u0026lt; 0.05\u003c/p\u003e","description":"","filename":"floatimage4.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7410912/v1/82aa31f324480c9f1320cfdc.jpeg"},{"id":93339370,"identity":"229c5291-2bc3-411c-a30a-d25758612b05","added_by":"auto","created_at":"2025-10-12 14:25:39","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":151197,"visible":true,"origin":"","legend":"\u003cp\u003eBroken line graph of the pelvis angles on the X-Y-Z axis with increasing FADP.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e(a)\u003c/strong\u003eX-axis: The sign of the forward tilt angle of the pelvis is positive, and the backward tilt angle is negative.\u003cstrong\u003e (b)(c)\u003c/strong\u003e Y-axis and Z-axis: The left‒righttilt angles of the pelvis on the Y-axis and the left‒right rotation angles of the pelvis on the Z-axis were taken as absolute values, and the smaller the values were, the smaller the differences in the left‒righttilt angle and left‒rightrotation angle were.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-7410912/v1/bbbac83406298fae329f5321.png"},{"id":101343484,"identity":"5cbe0201-a734-4044-9c49-107ed783b8c1","added_by":"auto","created_at":"2026-01-28 16:42:39","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1814036,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7410912/v1/73469ad0-90ee-4e63-8f64-dbcd050905a2.pdf"},{"id":93340700,"identity":"4354f9ce-be6c-4774-8805-04e2a53117c7","added_by":"auto","created_at":"2025-10-12 14:33:39","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":1367366,"visible":true,"origin":"","legend":"","description":"","filename":"supplementarydatafile.docx","url":"https://assets-eu.researchsquare.com/files/rs-7410912/v1/8d9210f6d40047f37c3b4916.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"The effect of Demi Plié in ballet on children with spastic cerebral palsy：A cross-sectional observational study","fulltext":[{"header":"1 INTRODUCTION","content":"\u003cp\u003eCerebral palsy (CP) is a neurological disorder that affects movement, posture, and balance and is accompanied by sensory, perceptual, cognitive, communication and behavior disorders[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. The primary neurological impairment affects muscle tone and secondary leads to joint contractures and bone deformities, such as equinus, stiff knee and torsional syndromes, causing lever arm dysfunction (LAD). The common LAD in the CP is torsion deformity in the horizontal plane, including femoral internal rotation and tibial internal rotation, and tibial internal rotation is more common than femoral internal rotation [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Torsion deformities of the lower limb are also associated with deformities associated with hip flexion, knee flexion and ankle eversion [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Femoral internal rotation reduces the lever arm of the hip abduction, resulting in an inability to produce hip abduction moments even if the hip abductor muscle strength is sufficient. Tibial torsion shortens the lever arm of ankle plantar flexion and knee extension, further exacerbating gait problems such as crouching [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eDance therapy, such as ballet therapy, is a promising therapeutic method for children with CP[\u003cspan additionalcitationids=\"CR7\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Demi Pli\u0026eacute; is the most basic movement in classical ballet. The Demi Pli\u0026eacute; movement requires keeping the torso upright while flexing the hip and knee, rotating externally, and dorsiflexing the ankle. Studies have shown that Demi Pli\u0026eacute; can activate the triceps calf, gluteus maximus, and gluteus medius, which may be beneficial for maintaining the posture of the CP [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. However, studies have reported that maintaining a large foot turn-out angle could cause medial misalignment of the knee relative to the ipsilateral foot, which can result in the accumulation of tension on the medial collateral ligament and serve as a predisposing factor for future injury [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. External hip rotation is used to compensate for the tension on the ankle and knee to achieve the maximum foot turn-out angle and potentially exaggerate the anterior pelvic tilt [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Some researchers believe that aligning the foot with the center of the knee is preferable and less damaging [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Owing to the gait pattern of the CP, it was difficult for them to achieve the standard turn-out angle of the foot and hip during Demi Pli\u0026eacute;.\u003c/p\u003e\u003cp\u003eThe effects of Demi Pli\u0026eacute; on CP have not been previously reported. The aim of this study was to observe the angles and moments of the lower limb joints of the CP at different foot turn-out angles of Demi Pli\u0026eacute; (FADP) and to determine whether Demi Pli\u0026eacute; may injure the CP and how to avoid it.\u003c/p\u003e"},{"header":"2 METHODS","content":"\u003cp\u003eThe trial and the statistical analysis plan were registered On February 23rd, 2021 at the Chinese Clinical Trial Registry (ChiCTR2100043593). The trial was approved by the Medical Ethics Committee of Shanghai Rehabilitation Institute for the Exceptional Children (China, Shanghai) (2020-072). The trial was an observational cross-sectional study and was conducted in accordance with the requirements of the STROBE Statement. Children aged 16 and below who participated in this experiment have obtained the informed consent of their parents or legal guardians.\u003c/p\u003e\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1 Participants\u003c/h2\u003e\u003cp\u003eAll measurements were performed in the gait analysis laboratory, at the Shanghai Rehabilitation Institute for the Exceptional Children, in Shanghai, China between from November 2021 to November 2022. Participants were recruited through advertisements, and all the subjects who met the eligibility criteria were invited by telephone. The CP group consisted of children aged 4 to 16 years with Gross Motor Function Classification System (GMFCS) grades I to II and no surgical history or botox injections within the past 6 months. The typically developing (TD) group included children from nearby communities. All the children were in good health, and both they and their parents voluntarily participated in this study. Those with severe cognitive and mental dysfunction and other serious systemic organic diseases (e.g., heart, liver, kidney and endocrine and metabolic disorders) were excluded. Data were excluded for children who were unable to complete the study as needed. In total, 20 children were included in each group for a total of 40 children for analysis.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2 Maker arrangement and demi pli\u0026eacute; movement\u003c/h2\u003e\u003cp\u003eMarkers were placed on each subject according to the modified conventional gait model[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. The following locations were marked: left and right posterior superior iliac spine, left and right anterosuperior iliac spine, left and right lateral thigh (marked with wand), left and right later shank (marked with wand), left and right tibial plateau (not included in the modified conventional gait model market set), left and right medial and lateral epicondyle of the femur, left and right medial and lateral malleolus, left and right 1st, 2nd and 5th metatarsal head and base, and left and right dome of the calcaneus (Fig .1). Demi Pli\u0026eacute; movement does in the second foot position of ballet: two heels on the ground in a straight line, toes turn out, feet one foot apart, and children perform a half squat movement, ensuring that their knee does not exceed the toe. According to classical ballet standards, the turn-out angle of the foot should be close to 180\u0026deg;, but this approach could be difficult for CP children. Previous studies have reported that this angle may cause injury to the lower limb joints [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. To address this, four progressive angles of the foot were chosen: 30\u0026deg;, 60\u0026deg;, 90\u0026deg;, and 120\u0026deg;.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eFig .1 Maker arrangement in the front and direction of virtual coordinate system construction.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3 Data collection\u003c/h2\u003e\u003cp\u003eThree-dimensional motion capture was performed via a twenty-camera motion tracking system (Motion Analysis Corp., Santa Rosa, CA), with twelve cameras on the ceiling and eight on the ground. The tracking system captured data at a frequency of 120 Hz. Biomechanical data were collected from the force platform (Bertec Corp., Worthington, British) at 1000 Hz. Cortices 2.2.1 were used to track the marker trajectories. The data collection process involved the following steps: first, the personal information (gender, age, BMI, GMFCS level and classification) was collected; then, a physical assessment (lower extremity passive joint angles and muscle tension test) was performed. In physical assessment, the popliteal angle measures the tension of the hamstring muscle, the thigh-foot angle (TFA) and transmalleolar axis (TMA) measure the torsional angle of the tibia, and the Q angle measures the knee valgus angle by measuring the angle between the line of the tibial tubercle and the long axis of the thigh. The subjects were brought to the lab, and data were collected as they performed Demi Pli\u0026eacute; movements at 30\u0026deg;, 60\u0026deg;, 90\u0026deg; and 120\u0026deg; of foot turn out. Because biomechanical data could not be obtained when the two feet were on the same force plate at the same time, data were captured for 3 instances with one side of the subject contacting the force plate at a time and then the other. Each turn was maintained for 10 s, followed by a rest period of 30 s. Two therapies were arranged to help the subjects complete the required movements.\u003c/p\u003e\u003cp\u003eIn the Cortex software, marker points were named, and a .c3d file was created and imported into Visual 3D (C-Motion, Inc., Germantown, MD). A virtual coordinate system was created in visual 3D, and the X, Y and Z axes of the virtual coordinate system represent the motion of the lower limb joints in the sagittal plane (extension/flexion), the coronal plane (inversion/eversion, adduction/abduction, varus/valgus) and the horizontal plane (internal/external rotation). The segments are defined by target markers at the proximal and distal joints. For example, the right thigh region was defined as follows: At the proximal (upper) end of the right thigh, the position of the right hip marker is used together to define the proximal endpoint. At the distal end, both medial and lateral knee markers are available and together define both the distal endpoint and the distal radius of the thigh segment. Any two segments in proximity to be \"linked\" and references a Joint. Angles and moments of the lower limb joint were processed via visual 3D.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.4 Statistical analysis\u003c/h2\u003e\u003cp\u003eStatistical analysis was performed via SPSS version 25.0 (Property of IBM Corp, New York, America). An alpha level of 0.05 was used to determine significance. Missing data were not included in the analysis. The significant differences in baseline parameters between the two groups were determined via the independent sample t test or Mann‒Whitney U test. Since the main parameters (joint angles and moments) at the progressive FADP (30\u0026deg;, 60\u0026deg;, 90\u0026deg;, 120\u0026deg;) were collected by the same subject each time, the intragroup data did not meet the condition of mutual independence. Therefore, a repeated-measures ANOVA was used as a priority, and a sphericity test was conducted to confirm the correlation between the data.\u003c/p\u003e\u003c/div\u003e"},{"header":"3 RESULTS","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e3.1 Clinical characteristics for each group\u003c/h2\u003e\u003cp\u003eTwenty children with CP and twenty TD children (aged 4\u0026ndash;16 years) completed the test. In each group, the proportions of males and females were equal (28 males and 12 females). The proportions of patients with GMFCSs Ⅰ and Ⅱ in the CP group were the same (GMFCS I:GMFCS II\u0026thinsp;=\u0026thinsp;10:10) and included both unilateral and bilateral involvement, with 65% being hemiplegic in the CP group. There were no intergroup differences in BMI values (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.156) (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eParticipant characteristics\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCharacteristic\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCP (n\u0026thinsp;=\u0026thinsp;20)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eTD (n\u0026thinsp;=\u0026thinsp;20)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAge, y\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e7.80\u0026thinsp;\u0026plusmn;\u0026thinsp;3.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e11.75\u0026thinsp;\u0026plusmn;\u0026thinsp;4.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSex, male/female\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e14/6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e14/6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.000\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBMI, kg/m\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e17.47\u0026thinsp;\u0026plusmn;\u0026thinsp;3.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e18.79\u0026thinsp;\u0026plusmn;\u0026thinsp;2.74\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.156\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGMFCS\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLevelⅠ/Ⅱ, n\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e10/10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eUnilateral/bilateral, n\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e13/7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003ePhysical assessment revealed significant differences between the two groups in hip abduction, ankle dorsiflexion with knee extension/flexion, ankle plantar flexion, torsion angle of the tibia (TFA, TMA) and the Q angle (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Compared with the TD group, the children in the CP group had limited angles of hip abduction, ankle plantar flexion and dorsiflexion but more tibial internal rotation. Popliteal angle, Ely and Thomas tests were significantly different between the two groups (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05), indicating that CP individuals had greater hamstring tension, iliopsoas tension and quadriceps tension and that these muscles play important roles in maintaining the stability of the lower limb chain (pelvic, hip, knee and ankle) [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan additionalcitationids=\"CR15\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eComparison of the physical assessment data between the two groups\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCP(mean and 95% CI)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eTD (mean and 95% CI)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eZ/x\u003csup\u003e2\u003c/sup\u003e value\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHip flexion ROM\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e135.0(126.2\u0026thinsp;~\u0026thinsp;138.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e135.0(133.50\u0026thinsp;~\u0026thinsp;140.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e-1.70\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.089\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHip extension ROM\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e11.0(10.0\u0026thinsp;~\u0026thinsp;12.76)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e12.00(11.00\u0026thinsp;~\u0026thinsp;13.00)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e-1.383\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.167\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHip internal rotation ROM\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e70.0(79.50\u0026thinsp;~\u0026thinsp;65.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e67.00(61.25\u0026thinsp;~\u0026thinsp;75.00)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e-1.693\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.091\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHip external rotation ROM\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e40.0(37.25\u0026thinsp;~\u0026thinsp;49.75)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e45.00(40.00\u0026thinsp;~\u0026thinsp;54.00)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e-1.861\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.063\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHip abduction ROM\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e51.5(44.00\u0026thinsp;~\u0026thinsp;58.00)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e54.00(50.00\u0026thinsp;~\u0026thinsp;60.00)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e-2.031\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.042*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eKnee flexion ROM\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e150.0(144.0\u0026thinsp;~\u0026thinsp;152.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e149.00(140.00\u0026thinsp;~\u0026thinsp;153.00)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e-0.540\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.589\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eKnee extension ROM\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.00(0.00\u0026thinsp;~\u0026thinsp;2.00)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.00(0.00\u0026thinsp;~\u0026thinsp;3.00)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e-0.384\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.701\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePopliteal angle\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e40.00(37.00\u0026thinsp;~\u0026thinsp;53.75)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e35.00(30.00\u0026thinsp;~\u0026thinsp;38.75)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e-4.564\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0 .001*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAnkle dorsiflexion ROM (Knee ext)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e5.50(-2.50\u0026thinsp;~\u0026thinsp;10.00)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e10.00(4.25\u0026thinsp;~\u0026thinsp;15.00)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e-3.109\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.002*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAnkle dorsiflexion ROM (Knee flexn)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e19.00(10.00\u0026thinsp;~\u0026thinsp;21.75)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e20.00(15.00\u0026thinsp;~\u0026thinsp;28.00)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e-2.388\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.017*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAnkle plantar flexion ROM\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e32.00(28.50\u0026thinsp;~\u0026thinsp;37.00)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e35.50(32.00\u0026thinsp;~\u0026thinsp;40.00)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e-2.318\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.020*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTFA\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-8.50(-11.75~-5.00)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-14.50(-18.75~-10.00)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e-4.552\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0 .001**\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTMA\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-9.50(-15.00~-5.00)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-15.50(-20.00~-11.00)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e-3.828\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0 .001**\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eQ angle\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-2.00(-3.00~-2.00)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-3.00(-4.00~-2.00)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e-2.323\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.020*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eEly test(Rectus femoris muscle tension test)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e+\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e5.165\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.023*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eThomas test(Iliopsoas muscle tension test)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e+\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e11.429\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.001*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"5\"\u003e\u003cem\u003eNote\u003c/em\u003e: The inverted/varus/adduction angles are positive, and the eversion/valgus/abduction angles are negative. *\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05; **\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001. TFA, Thighfoot angle. TMA, transmalleolar axis.\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e3.2 Ankle parameters\u003c/h2\u003e\u003cp\u003eAnkle parameters (as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e2\u003c/span\u003e) revealed that there was a significant effect of FADP in the ankle angles on the X‒Y‒Z axes (sagittal, coronal, and horizontal planes) (intragroup differences, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The external rotation and eversion angles of the ankle increased with increasing FADP. There was a significant effect of FADP on ankle moments on the Y-axis and Z-axis (coronal and horizontal planes) (intragroup differences \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026le;\u0026thinsp;0.001). The external rotation moment of the angle decreased with increasing FADP and then became an internal rotation moment at 120\u0026deg; of the FADP. The eversion moment of the ankle increased with increasing FADP, which was greater in the TD group than in the CP group.\u003c/p\u003e\n\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\n \u003ch2\u003e3.3 Knee parameters\u003c/h2\u003e\n \u003cp\u003eKnee parameters (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e) revealed that there was a significant effect of FADP (intragroup differences \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0 .001) on the knee angle on the Z-axis (horizontal plane). The external rotation angle of the tibia increased with increasing FADP. The extension moment of the knee on the X-axis (sagittal plane) in the CP group was less than that in the TD group (intergroup difference \u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.021). Although there was no intragroup or intergroup difference in the knee moment on the Z-axis (horizontal plane), both groups tended to increase the internal rotation moment after 60\u0026deg; of FADP.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\n \u003ch2\u003e3.4 Hip parameters\u003c/h2\u003e\n \u003cp\u003eHip parameters (Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e) revealed a significant effect of FADP (intragroup \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001) on hip angles on the Y-axis and Z-axis (coronal and horizontal planes). The hip abduction angle and hip external rotation angle increased with increasing FADP in both groups. There were also intergroup (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.050) differences; the hip abduction angle was greater in the CP group than in the TD group, whereas the hip external rotation angle in the CP group was less than that in the TD group. There was a significant effect of FADP on hip moments on the X-axis (sagittal plane) (intragroup \u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.044) and on hip moments on the Y-axis (coronal plane) (intragroup \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0 .001). With increasing FADP, both groups generated hip flexion moments at 90\u0026deg; or 120\u0026deg; of the FADP. The hip abduction moment decreased in both groups until the adduction moment was reached in the CP group at 120\u0026deg; FADP, and the hip abduction moment was greater in the TD group than in the CP group (intergroup \u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.001).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\n \u003ch2\u003e3.5 Pelvic parameters\u003c/h2\u003e\n \u003cp\u003ePelvic parameters (Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e) revealed significant intergroup differences (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.001) in the pelvis angle between the two groups in the Z-axis (horizontal plane), and the rotation of the pelvis angle (absolute rotation deviation) in the horizontal plane in the CP group was greater than that in the TD group.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"4 DISCUSSION","content":"\u003cp\u003eThis study aimed to observe the angles and moments of the lower limb joints of the CP at different foot turn-out angles of Demi Pli\u0026eacute; and to determine whether Demi Pli\u0026eacute; may injure the CP and how to avoid it. The results preliminarily showed that the large angle of FADP, such as 90\u0026deg; or 120\u0026deg; of Demi Pli\u0026eacute; movement in ballet training, may cause excessive stress to the joint and lead to injury to the CP.\u003c/p\u003e\u003cp\u003eThe results of the ankle data revealed that after 30\u0026deg; of FADP, the ankle dorsiflexion angles and plantar flexion moments in the CP group decreased gradually with increasing FADP, and the ankle eversion angles and eversion moments increased in both groups. This means that the increasing angles of FADP may aggravate the LAD problem of valgus deformities such as pes planus in the CP. These results have also been reported in previous studies on ballet dancers, which indicate that to maintain a larger FADP, the arch of the foot drops, and the foot tends to pronate[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e], which further leads to injury of the medial meniscus and medial collateral ligament of the knee with an increasing tendency toward knee valgus[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe results of the knee data revealed that an increase in the FADP led to greater external rotation of the tibia in both groups. This finding indicated that Demi Pli\u0026eacute; may be beneficial for improving the external rotation angle of the tibia in the CP, according to the physical assessment results: the CP had more tibial internal rotation than did the TD. However, the knee extension moment in the CP group was significantly smaller than that in the TD group, indicating that the strength of the knee extensors in the CP group during Demi Pli\u0026eacute; was still weaker than that in the TD group. This may be due to the greater degree of knee flexion in the CP group due to the weakness of the knee extensors (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003e), which may further exacerbate LAD problems in CP individuals who have a crouching gait characterized by flexion deformities of the knee and hip.\u003c/p\u003e\u003cp\u003eThe results of the hip data revealed that with increasing FADP, the hip abduction angle and hip external rotation angle increased in both groups. The hip abduction angle in the CP group was larger than that in the TD group, whereas the abduction moment was smaller than that in the TD group. The intergroup difference in the abductor moment suggested that the strength of the hip abductor muscle group in the CP was relatively weak, and to maintain balance, the CP seems to compensate by increasing the angle of hip abduction and external rotation and widening the distance between their feet. In Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003e, at 30\u0026deg;, 60\u0026deg; and 90\u0026deg; of FADP, the line of hip abduction moment data of the CP group was above the critical boundary (\u0026ge;\u0026thinsp;0), indicating that the hip abductor muscle was active during Demi Pli\u0026eacute; and may be helpful for the CP. However, it is important to note that a large angle of FADP may be unfavorable for CP individuals. The hip adduction moment was generated in the CP group at 120\u0026deg; of FADP, and the hip flexion moment was generated in both groups at 90\u0026deg; of FADP. Combined with the data of the pelvis shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e5\u003c/span\u003e, we found that with increasing FADP, the angles of the pelvis in the horizontal plane and coronal plane increased in the CP group. On the basis of these observational results, we speculate that increasing the FADP angle may lead to increased hip flexion compensation and pelvic instability in the CP.\u003c/p\u003e"},{"header":"5 CONCLUSION","content":"\u003cp\u003eIn conclusion, the Demi Pli\u0026eacute; movement in ballet training for CP children needs to be regulated. A large FADP angle, such as 90\u0026deg; or 120\u0026deg;, may cause excessive stress on the joint and lead to injury to the CP, especially those who have a crouching gait with hyperflexion of the knee and hip and deformity of the pes planus (ankle eversion).However, further investigations of the long-term effects of the Demi Pli\u0026eacute; movement on the CP are needed to confirm these conclusions.\u003c/p\u003e\u003cp\u003eThis is the first study to explore the effect of the Demi Pli\u0026eacute; movement on children with CP. However, as an advanced observational study, this study has several limitations. For example, only immediate data were collected during a trial, and the generalizability of the study results is limited. In addition, only CP children with GMFCS grades Ⅰ-Ⅱ were included for observation and analysis in the trial because of the difficulty of performing the Demi Pli\u0026eacute; movement for children with high motor dysfunction. Although not all types of CP were included in this study, the results are beneficial for CP who practice dance, especially ballet dance, to avoid possible injury and help develop appropriate dance training plans.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eCP Cerebral palsy\u003c/p\u003e\u003cp\u003eFADP Foot turn-out angle of Demi Pli\u0026eacute;\u003c/p\u003e\u003cp\u003eLAD Lever arm dysfunction\u003c/p\u003e\u003cp\u003eTD Typically, developing group\u003c/p\u003e\u003cp\u003eTFA Thigh-foot angle\u003c/p\u003e\u003cp\u003eTMA Transmalleolar axis\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study has been inspired by Professor Deborah Gaebler Spira, who has given us a lot of guidance during research.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eJie Ren\u0026nbsp;wrote the original manuscript. Chunxin Xu was responsible for supervising the project and the final review. Yangyang Lu analyzed the data. Cen Chen and Shenyu Zhu participated in the clinical investigation. Min Shen\u0026nbsp;was responsible for the entire project.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eData is provided within the manuscript or supplementary information files.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was approved by the Medical Ethics Committee of Shanghai Rehabilitation Institute for the Exceptional Children (China, Shanghai) (2020-072).\u0026nbsp;Children aged 16 and below who participated in this experiment have obtained the informed consent of their parents or legal guardians. The study was conducted in accordance with the Declaration of Helsinki (https://www.wma.net/policies-post/wma-declaration-of-helsinki/).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eConsent for publication has been obtained from children or their parent or legal guardian.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eWimalasundera N, Stevenson VL. Cerebral palsy. 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Overuse injuries in classical ballet. Sports Med. 1995;19(5):341\u0026ndash;57. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.2165/00007256-199519050-00004\u003c/span\u003e\u003cspan address=\"10.2165/00007256-199519050-00004\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Dance therapy, Ballet, Cerebral palsy, Three-dimensional motion","lastPublishedDoi":"10.21203/rs.3.rs-7410912/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7410912/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e\u003cp\u003eDemi Pli\u0026eacute; is the most basic movement in classical ballet. Previous studies have shown that Demi Pli\u0026eacute; may be beneficial for maintaining the posture of patients with cerebral palsy. However, studies also reported that Demi Pli\u0026eacute; caused injury. The aim of this study was to observe the angles and moments of the lower limb joints of cerebral palsy at different foot turn-out angle of Demi Pli\u0026eacute;.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e\u003cp\u003eA cross-sectional observational study was conducted and divided into two group. Joint angles and moments were collected during Demi Pli\u0026eacute; at progressive foot turn-out angles (30\u0026deg;, 60\u0026deg;, 90\u0026deg; and 120\u0026deg;).\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e\u003cp\u003eWith the increase of foot turn-out angles, the external rotation and eversion angles of the ankle increased(\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001), and the eversion moments of ankle increased while the external rotation moments of ankle decreased(\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026le;\u0026thinsp;0.001). The external rotation angles of tibia increased with increasing turn-out angles (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The extension moments of knee in cerebral palsy group was less than that in the typically developing group (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.021). Hip abduction angles and hip external rotation angles in both groups increased with the increase of turn-out angles(\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001), while hip extension moments and hip abduction moments decreased(\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Pelvis rotation angles were greater in cerebral palsy group compared to typically developing group.\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e\u003cp\u003eA large turn-out angle (90\u0026deg; or 120\u0026deg;) may cause excessive stress to lower limb joints, leading to injury in cerebral palsy patients, especially those who have a crouching gait with hyperflexion of the knee and hip and deformities associated with ankle eversion.\u003c/p\u003e\u003ch2\u003eTrial Registration\u003c/h2\u003e\u003cp\u003eThe trial was registered with the full protocol accessible through Chinese Clinical Trial Registry (ChiCTR) website(https//www.chictr.org.cn/) on February 23rd, 2021. Trial registration number ChiCTR2100043593.\u003c/p\u003e","manuscriptTitle":"The effect of Demi Plié in ballet on children with spastic cerebral palsy：A cross-sectional observational study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-10-12 14:25:35","doi":"10.21203/rs.3.rs-7410912/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"c8ed489c-875e-4a80-bf82-760ea78cc711","owner":[],"postedDate":"October 12th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-01-28T16:42:21+00:00","versionOfRecord":[],"versionCreatedAt":"2025-10-12 14:25:35","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7410912","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7410912","identity":"rs-7410912","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}