Multi-segment spine range of motion in dancers with and without recent low back pain

BackgroundAltered spine kinematics are a common in people with LBP. This may be especially true for populations such as dancers, who are required to perform repetitive movements of the spine, although this remains unclear.Research questionDo dancers with recent LBP display altered spine kinematics compared to their asymptomatic counterparts?MethodsA cross-sectional study of multi-segment spine kinematics was performed. Forty-seven pre-professional and professional female dancers either with LBP in the past two months (n = 26) or no LBP in the past 12 months (n = 21) participated. Range of motion (ROM) during standing side bending, seated rotation, and walking gait were compared.ResultsFemale dancers with LBP displayed reduced upper lumbar transverse plane ROM in seated rotation (Effect Size (ES)= −0.61, 95% Confidence Interval (CI): −1.20, 0.02, p = 0.04), as well as reduced lower lumbar transverse plane ROM (ES=−0.65, 95% CI: −1.24, −0.06, p = 0.03) in gait. However, there was increased lower thoracic transverse plane ROM (ES = 0.62, 95% CI: 0.04, 1.21, p = 0.04) during gait. No differences in the frontal plane were observed.SignificanceAltered transverse plane spine kinematics were evident in dancers with recent LBP for select segments and tasks. This may reflect a protective movement strategy. However, as the effect sizes of observed differences were moderate, and the total number of differences between groups was small, collectively, it seems only subtle differences in spine kinematics differentiate dancers with LBP to dancers without.     

The effect of latin dance on dynamic balance

BackgroundFigures and movements in Latin dance are effectively used to provide posture stabilization and balance control. A Computerized Dynamic Posturography can be used to complete a functional evaluation of postural control and stability in static and dynamic conditions, mediated by the interaction between the visual, vestibular, and somatosensory systems.Research QuestionAccording to the results of Computerized Dynamic Posturography, do dancers have better postural control and stability when compared to non-dancers, and can dance activity be recommended for vestibular rehabilitation?Material and methodsOur study included 26 professional Latin dancers and 26 non-dancers as a control group whoboth had no problems with their hearing or balance. Pure-tone audiometry and Computerized Dynamic Posturography tests were applied to the participants. The test results for the professional dancers and the control group were compared and evaluated. In statistical analysis, the Mann-Whitney U and Independent Samples T tests were used. A value of p < 0.05 was accepted for significance.ResultsAccording to the results of the Computerized Dynamic Posturography, the dancers generally performed better than the control group. While statistically significant and better performances were observed in dancers in terms of the composite balance, visual and vestibular scores within the scope of the Sensory Organization Test (p < 0.05), no statistically significant difference was found for somatosensory and preference scores (p > 0.05). Also, significant differences were obtained between the two groups in some subtests of Adaptation, Unilateral Stance and Limits of Stability assessment (p < 0.05). No significant difference was observed in Rhythmic Weight Shift results (p > 0.05).ImportanceThe results of thisresearch demonstrate that balance and posture improve through dance. Therefore, adding appropriate dance activities to vestibular rehabilitation programmes might be helpful.     

Patients with chronic non-specific low back pain have altered movement coordination during functional reaching tasks

BackgroundIdentifying altered motor control patterns during functional movements in patients with chronic non-specific low back pain (LBP) has important clinical implications for reducing the risk of recurrence. While prior research has shown that magnitudes of lumbar and hip motion are not altered in patients with chronic non-specific LBP, it is possible that outcomes which describe coordination could provide greater discriminatory information between pathological and healthy movement.Research questionDetermine the effect of biological sex and chronic non-specific LBP on coordination between hip and lumbar motion during cyclic and discrete reaching.MethodsTwenty participants with chronic non-specific LBP (11 male/9 female, 23.5 ± 4.9 years old) and 21 control participants (12 male/9 female, 22.9 ± 6.1 years old) completed discrete and cyclic reaching tasks to a target in the mid-sagittal plane, while whole-body kinematics were collected using a three-dimensional motion capture system. Movement time, lumbar motion, hip motion, and the ratio between lumbar and hip motion were compared between participants with and without chronic non-specific LBP and between men and women using two-way mixed ANOVAs.ResultsParticipants with chronic non-specific LBP had reduced lumbar-hip ratios relative to control participants during both the cyclic (F = 4.779, p = 0.035, η² = 0.114) and discrete tasks (F = 4.743, p = 0.036, η² = 0.119), however group differences were not observed for hip or lumbar excursion during either task (p > 0.05). Participants with chronic non-specific LBP had slower reaching times relative to controls during the discrete reaching task (F = 4.795, p = 0.035, η² = 0.115). No significant effects of sex, and no interactions between group and sex were observed for any outcome.SignificanceReduced lumbar-hip ratios during reaching likely reflect a compensatory movement strategy that could play an important role in the development and progression of LBP.     

Motion of the multi-segmented spine in elite dancers during passé and arabesque

BackgroundThe spinal biomechanics of dance tasks have received little study and no studies have used a multi-segmented spinal model. Knowledge of how the segments of the spine move may be useful to the dance clinician and dance educator.Research questionWhat is the direction and amount of motion of the primary segments of the spine in elite dancers during an arabesque and a passé?MethodsThis observational study examined 59 elite dancers performing an arabesque and a passé using a three-dimensional motion analysis system with the trunk divided into a series of five segments: pelvis, lower lumbar, upper lumbar, lower thoracic and upper thoracic spine.ResultsFor the arabesque, all spinal segments moved in the same direction within each plane and the majority of total spinal motion occurred in the thoracic spine. Thoracic segments were at or near end range position at completion of the arabesque. For the passé, the spinal segments moved in different directions within each plane and the majority of total spinal motion occurred in the lumbar spine.SignificanceDance clinicians and dance educators may benefit from the knowledge that thoracic hypomobility in any plane may limit arabesque performance and that attempts to instruct dancers to achieve a position of passé without flexion of the lumbar spine may be a valid aesthetic ideal but also an unrealistic functional expectation.     

Influence of dance training on challenging postural control task

BackgroundPrevious studies have shown that dance training affects postural control, particularly during challenging tasks. However, it is still unknown whether dance training also affects the ability to use vestibular, somatosensory, and visual cues, thus leading to postural control differences.ObjectiveThe main goal of the present study was to evaluate the influence of dance training on sensory weighting during static postural control.MethodThe center of pressure of 24 participants was recorded (12 dancers and 12 control non-dancers) using a force platform as well as the modified Clinical Test of Sensory Organization in Balance (mCTISB).ResultsThe results suggest that dancers perform significantly better than controls in conditions where somatosensory cues are disturbed. Moreover, a significant negative correlation between vestibular frequency band and training intensity was observed, along with, a significant positive correlation between visual frequency band and training intensity.SignificanceThis research outlines dancers’ increased ability to modulate sensory weighting differently than non-dancers during postural task where somatosensory cues are reduced.     

Schulterverletzungen im Lateinamerikanischen Formationstanz

BackgroundCharacteristic for Latin American formation dance are turning-,catapulting- and pulling movements affecting the shoulder-arm-region. The aim of thisstudy is to analyse shoulder injuries in Latin American formation dancers.Material and methodsA total of n=81 dancers (m: n= 43; w: n= 38) volunteered for thisretrospective cross-sectional cohort study using questionnaires.Results22.8% (m: 21.9%, f: 23.7%, p= 0.310) of dancers suffered from shoulderinjuries at least once during a 12-month period. Gender-specific non-significant differences regarding the affected side (f: right 80%, left 13.3%; m: right: 38.5%, left 46.2%, p=0.429) were observed. Most of the shoulder injuries occurred during the technically maximum difficulties (m: 76.9%; f: 73.3%, p= 0.675) characteristic for Latin American formation dance. 31.6% of the female dancers (m: 29.3% vs. f: 34.2%, p=0.884) reported to suffer from chronic shoulder damage (right>left: m: 41.7% vs. f:38.5%, p= 0.137).ConclusionThe results reveal the need to consider an additive coordination-, strength- and stabilization training for the shoulder girdle. However, further studies with a higher number of cases are necessary in order to identify risk factors for shoulder problems and to finally clarify the existing gender-specific aspects.     

Comparison of lumbopelvic and dynamic stability between dancers and non-dancers

ObjectiveTo compare lumbopelvic stability between dancers and non-dancers by assessing lumbopelvic motor control, abdominal muscles automatic-activation, lumbar range of motion and dynamic stability.DesignCross-sectional.SettingUniversity/superior-dance-conservatory.ParticipantsTwenty-two dancers and 22 non-dancers.Main outcome measurementsThe active straight leg raise test (ASLR) was used to test lumbopelvic motor control with pressure feedback (mmHg). Transversus, rectus anterior and internal oblique muscles thicknesses were measured at rest and ASLR. For dynamic stability, the modified Star Excursion Balance Test (mSEBT) was employed.ResultsSignificant differences were revealed in lumbopelvic motor control between groups (p < 0.001). Abdominal muscles automatic-activation showed no differences between the groups. There were significant differences in the mSEBT for most of the test's directions, with dancers performing better than the non-dancers (p < 0.05). For the dancers, there were positive associations between motor control and dynamic stability, and between abdominal muscle thickness and mSEBT. For non-dancers, the rectus anterior activation correlated with the mSEBT.ConclusionsThe dancers had better lumbopelvic motor control, dynamic stability and lumbar movements except in terms of extension, as compared with non-dancers. Therefore, this novel study could stimulate a new line of research to determine the influence of these outcomes on sports performance, prevention and injury rehabilitation.     

The association between menarche,intensity of training and passive joint ROM in young pre-professional female dancers: A longitudinal follow-up study

ObjectivesTo determine the association between the status of menarche (yes/no), the intensity of training and the potential to improve passive joint range of motion (ROM) over a 12-month period of dance training.DesignProspective cohort study.SettingDance studio.ParticipantsFifty-nine female dancers aged 12.8 ± 0.5.Main outcome measuresThe dancers were asked about their dance intensity and screened for anthropometric parameters and passive joint ROM in Grades 7 and 8.ResultsAlong the 12 months of dance training, we found significantly increased ankle-foot en-pointe, hip abduction, and hip external rotation (ER); significantly decreased hip internal rotation (IR); and significant increased hip ER:IR ratio. In Grade 7, 26 dancers (44.1%) reached menarche (Yes menarche); in Grade 8 an additional 23 dancers (39.0%) reached menarche (No/Yes menarche); and 10 dancers (16.9%) had not reached menarche (No menarche). MANOVA (mixed models) with repeated measures to compare joint ROM between the three menarche groups (Yes; No/Yes; No), with h/week dance practice as a co-variant, showed that hip ER, ankle-foot en-pointe, and ER:IR were significantly correlated with h/week in all three menarche groups.ConclusionsMost passive joint ROM can be improved over 12 months of dancing around the age onset of menarche. H/week of dance practice is a main factor contributing to improved hip ER, ankle-foot en-pointe and ER/IR ratio.     

Life history and point prevalence of low back pain in pre-professional and professional dancers

ObjectivesTo investigate lifetime history and point prevalence of low back pain (LBP) in pre-professional and professional dancers and to identify any demographic or physical factors associated with LBP in dancers.DesignCross-sectional study.SettingOne pre-professional ballet school, two pre-professional university dance programs, and a professional nationally touring ballet company.ParticipantsMale and female classical ballet and contemporary dancers aged 12 years old and above.Main outcome measuresLifetime history and point prevalence of LBP.ResultsA total of 110 (n = 19 male) dancers (mean (SD) 17.8 (2.9) years old) participated in the study, which represented 50% of the population invited to participate. A 74% lifetime prevalence of LBP was reported by dancers. Point and 12 month prevalence were 24 and 64%, respectively. No significant association was observed between LBP and any demographic or physical variables.ConclusionPre-professional and professional dancers have an increased vulnerability to LBP. The development of LBP within this population is complex and may not be associated with individual factors measured in this study.     

An evaluation of differences in hip external rotation strength and range of motion between female dancers and non-dancers

Objectives: To evaluate the differences in hip external rotation (ER) strength and inner, outer, and total hip ER range of motion (ROM) between dancers and non-dancers and between left and right sides in each group.

Methods: Seventy one subjects (34 dancers and 37 non-dancers) volunteered for this study. The strength (truncated range average torque (TRAT), work, and angle specific torque (AST)) of the hip external rotator muscle group, through the full available active hip ER ROM, was evaluated using concentric isokinetic (30°/s) testing on a KinCom dynamometer. Adjustment for lean body mass (LBM) was made for comparison of strength between groups. A two way repeated analysis of covariance was used to compare strength between groups. A two way repeated analysis of variance was used to compare strength between sides and ROM between groups and sides. Bonferroni correction was made for multiple analyses, and significance was accepted at p0.05.

Results: AST at 0°, 20°, 30°, and 40° of hip ER was greater in the dancers than the non-dancers (p0.022). TRAT, work, AST_0°, AST_20°, and AST_30° of hip ER were all greater on the right side than the left (p = 0.007) in both groups. Dancers had greater inner ER ROM (p = 0.013) and less outer ER ROM than non-dancers (p0.001). There was no difference in total ER ROM between groups (p = 0.133). The right side had greater inner ER (p0.001) and total ER ROM (p0.001) than the left in both groups.

Conclusions: Ballet dancers have greater inner range, angle specific strength and inner range ER ROM, demonstrated by a shift in the dancers' strength curves. This shift in the strength curve towards the inner range of hip ER may be an adaptive training response.

     

Comparison of 3D spinal motions during stair-climbing between individuals with and without low back pain

In spite of the importance of stair-climbing (SC) as an activity of daily living, 3D spinal motion during SC has not been investigated in association with low back pain (LBP). The purpose of this research is to investigate the differences of the spinal motions during SC between an LBP group and a healthy control group, in order to provide insight into the LBP effect on the spinal motions. During two types of SC tests (single and double step SCs), we measured 3D angular motions (flexion/extension, lateral bending, and twist) of the pelvis, lumbar spine and thoracic spine using an inertial sensing-based, portable spinal motion measurement system. For the nine motion variables (i.e. three anatomical planes × three segments), range of motions (ROM) and movement patterns were compared to determine the differences between the two groups. It was found that the only variable having the p-value of a t-test lower than 0.05 was the flexion/extension of the lumbar spine in both SCs (i.e. the LBP group's ROM < the control group's ROM). Although the strength of this finding is limited due to the small number of subjects (i.e. 10 subjects for each group) and the small ROM differences between the groups, the comparison result of the t-test along with the motion pattern shows that the effect of LBP during SC may be localized to the lumbar spinal flexion/extension, making it an important measure to be considered in the rehabilitation and treatment of LBP patients.     

Differences in lower limb biomechanics between ballet dancers and non-dancers during functional landing tasks

ObjectivesTo determine the differences in the lower limb landing biomechanics of adolescent ballet dancers compared to non-dancers when performing a hop and a stop jump task.DesignCross-sectional.SettingLaboratory.ParticipantsThirteen adolescent female ballet dancers (11.8 ± 1.1 years) and 17 non-dancers (10.9 ± 0.8 years) performed hop and stop jump tasks.Main outcome measuresVertical ground reaction force, and three-dimensional ankle, knee and hip joint angles and moments during the landing phase.ResultsDancers displayed greater sagittal plane joint excursions during the hop and stop jump at the ankle (mean difference = 22.0°, P < 0.001, 14.8°, P < 0.001 respectively), knee (mean difference = 18.1°, P = 0.001, 9.8°, P = 0.002 respectively) and hip (stop jump task; mean difference = 8.3°, P = 0.008). Dancers displayed a larger hip extensor moment compared to non-dancers (P < 0.001) during the stop jump task only. Dancers also took longer to reach peak vGRF and jumped three times higher than non-dancers (P < 0.001) during the stop jump task. No difference in peak vGRF between groups was displayed for either task.ConclusionsAdolescent dancers demonstrate a transfer of landing technique to non-ballet specific tasks, reflective of the greater jump height and sagittal plane joint excursions. This landing strategy may be associated with the low rate of non-contact ACL injuries in female dancers.     

Lower limb joint angles and their variability during uphill walking

BackgroundAdaptation of the walking pattern to uphill walking demands immediate coordination between the lower limb segments. Nonetheless, knowledge about individual joints’ responses and variability in response to the new slope angles are missing.AimsThis study investigated the impacts of uphill walking on the ankle, the knee and the hip joints angles and their variability.MethodsTwenty-three collegiate athletes (age: 22.04 ± 3.43years, body mass: 62.14 ± 9.26Kg, height: 168.29 ± 7.06 cm) walked on an inclined treadmill at 0 ° (level walking -LW), 5 ° (low-slope-walking -LSW), and 10 ° (high-slope-walking -HSW) slopes at their preferred walking speed (4.2 ± 0.51 km.h⁻¹). The ankle, knee and hip joints angles and their variability (standard deviations) were calculated and analysed throughout the gait cycles in LW, LSW, and HSW.ResultsRepeated measure ANOVA portrayed significant differences between the ankle joint angles in sagittal (p < .001, η_p²>.14), frontal (p < .05, η_p²>.14), and transverse (p < .005, .14 < η_p²>.01) planes. In the knee joint, the sagittal (p < .001, η_p²>.14), frontal (p < .05, η_p²>.14), and transverse (p < .05, η_p²>.14) angles were significantly different (p < 0.05). Similarly, in the hip joint, the sagittal (p < .05, η_p²>.14), frontal (p < .05, η_p²>.14), and transverse (p < .05, η_p²>.14) angles were significantly different. Ankle angle variability was significantly different in sagittal (P < .001, η_p²>.14), frontal (p = .002, η_p²>.14) and horizontal (P < .001, η_p²>.14) planes, as well as knee joint angle variability in sagittal, frontal and horizontal planes p < 0.001, η_p²>.14. The hip joint variability was considerably different in sagittal (p = .031, η_p²>.14) and horizontal (p < .05, η_p²>.14) planes.ConclusionUphill walking involves further modifications in the ankle, knee and hip joints angle to adjust the whole-body movements to a new slope. This adjustment resulted in a firm base of support, provided by the ankle, to regulate the knee and hip joints modifications. Nevertheless, it caused less ankle movement variability and could end up with injuries over long-term uphill walking.     

Spinal fusion limits upper body range of motion during gait without inducing compensatory mechanisms in adolescent idiopathic scoliosis patients

IntroductionPrevious studies show a limited alteration of gait at normal walking speed after spinal fusion surgery for adolescent idiopathic scoliosis (AIS), despite the presumed essential role of spinal mobility during gait. This study analyses how spinal fusion affects gait at more challenging walking speeds. More specifically, we investigated whether thoracic-pelvic rotations are reduced to a larger extent at higher gait speeds and whether compensatory mechanisms above and below the stiffened spine are present.Methods18 AIS patients underwent gait analysis at increasing walking speeds (0.45 to 2.22 m/s) before and after spinal fusion. The range of motion (ROM) of the upper (thorax, thoracic-pelvic and pelvis) and lower body (hip, knee and ankle) was determined in all three planes. Spatiotemporal parameters of interest were stride length and cadence.ResultsSpinal fusion diminished transverse plane thoracic-pelvic ROM and this difference was more explicit at higher walking speeds. Transversal pelvis ROM was also decreased but this effect was not affected by speed. Lower body ROM, step length and cadence remained unaffected.DiscussionDespite the reduction of upper body ROM after spine surgery during high speed gait, no altered spatiotemporal parameters or increased compensatory ROM above or below the fusion (i.e. in the shoulder girdle or lower extremities) was identified. Thus, it remains unclear how patients can cope so well with such major surgery. Future studies should focus on analyzing the kinematics of individual spinal levels above and below the fusion during gait to investigate possible compensatory mechanisms within the spine.     

Obturator externus was larger,while obturator internus size was similar in ballet dancers compared to nondancing athletes

ObjectivesTo compare the cross-sectional area (CSA) of hip external rotators, obturator externus (OE) and obturator internus (OI), in ballet dancers and nondancing athletes, and evaluate the relationship between obturator muscle size and hip pain.DesignCase-control study.SettingElite ballet and sport.Participants33 male and female professional ballet dancers and 33 age and sex-matched athletes.Main outcome measuresCSA's of OE and OI measured on magnetic resonance imaging (MRI) of one hip. Hip pain was scored with the Copenhagen Hip and Groin Outcome Score (HAGOS): HAGOS pain score of 100 was defined as no pain and a score less than 100 was defined as pain. Participants weight and height.ResultsEstimated marginal mean CSA of OE was 14% larger in dancers than athletes (p = 0.01, ηp2 = 0.1); the size of OI was similar (p > 0.05). Men and women in both groups had similar sized OI and OE. There was no interaction between the estimated marginal mean CSA of either obturator and hip pain.ConclusionsIt appears that ballet selectively increases muscle size of OE, but not OI. Obturator size was not related to mild hip pain, as OE and OI size was similar in dancers and athletes with and without pain.     

Musculoskeletal profile of the lumbar spine and hip regions in cricket fast bowlers

ObjectivesTo determine the career history of low back pain (LBP) in current elite female cricket fast bowlers and then compare measures of lumbar spine and hip range of motion (ROM) and trunk extensor endurance between those bowlers with and without a history of LBP. Measures for the female bowlers were also compared to a small sample of male fast bowlers.ParticipantsTwenty-six elite female fast bowlers and eight male fast bowlers of similar age and bowling experience.Main outcome measuresThe career history of LBP was determined by a self-administered questionnaire and by accessing medical records. Range of motion measures for the lumbar spine and hips were obtained using inclinometry or goniometry. Trunk extensor endurance was assessed using a modified Sorensen test.ResultsFourteen female fast bowlers had a history of LBP. There was a significant difference in lumbar lateral flexion ROM to the bowling arm side between those female fast bowlers with and without a history of LBP (p⩽0.05). The female fast bowlers had significantly more bilateral hip extension ROM (p⩽0.05) compared to the male fast bowlers.ConclusionsThis information should be useful for practitioners involved in the conditioning and rehabilitation of cricketers. Future prospective studies should investigate potential predictors of LBP in female fast bowlers.     

The relationship of trunk kinematics and kinetics with lower limb pathology during gait in children with spastic cerebral palsy

BackgroundTrunk control during gait in children with cerebral palsy (CP) is known to be impaired. While differentiation of trunk movement between CP subtypes (unilateral/bilateral) has been examined, differentiation of lower lumbar spinal loading has not been considered. Furthermore, the relationship between lower lumbar loading and lower limb pathology has not been reported.Research QuestionHow do lower lumbar spinal kinetics differ during unilateral and bilateral CP gait and what is the relationship between trunk kinematics and L5/S1 kinetics with lower limb pathology?MethodsThree-dimensional thorax kinematics and L5/S1 kinetics were measured during gait with children divided into 3 groups (unilateral CP (n = 21), bilateral CP (n = 31) and typical development (TD) (n = 26)). Differences in thorax kinematics and reactive forces and moments at L5/S1 between groups were analysed using Statistical Parametric Mapping. Correlation coefficients were calculated between Gait Profile Score (GPS) and kinematic measures of the thorax and kinetics at L5/S1.ResultsAn increased ipsilateral bending moment was present for unilateral CP in the coronal plane (55–70% Gait Cycle (GC), p < 0.001), while children with bilateral CP demonstrated two distinct increased peaks during mid-stance (10–30 % GC, p < 0.001) and mid-swing (60–80% GC, p = 0.004) compared to TD. RMS and RoM thorax flexion, side flexion and L5/S1 lateral bend moment demonstrated significant moderate correlations with GPS.SignificanceThis study confirmed an increased involvement at the trunk and of lower lumbar spinal loading for children with bilateral CP compared to unilateral CP. It has been suggested that altered trunk movement in CP gait may be a combination of both a compensation for lower limb pathology and an underlying deficit. Our result of positive yet moderate correlations between GPS and trunk movement and lower spinal loading support this theory.     

Ultrasound imaging features of the Achilles tendon in dancers. Is there a correlation between the imaging and clinical findings? A cross-sectional study

ObjectivesTo analyze the prevalence of tendon pathology and performance associated in pre-professional classic dancers with no history of Achilles tendon (AT) pain. Design: A cross-sectional study was conducted.ParticipantsTwenty-nine classic ballet dancers without AT pain (58 tendons) were recruited. The tendons were classified (normal, abnormal) using ultrasound imaging (USI). Cross-sectional area (CSA) and thickness of flexor hallucis longus (FHL) muscle were measured using USI. Range of movement (ROM) of the first metatarsophalangeal join, balance test, endurance test and vertical jump were measured (bilaterally) as performance variables.ResultsMore than a half (62%) of the participants had at least one abnormal tendon, with 45% of the dancers in the abnormal group having bilateral abnormalities. Dancers with AT pathology had significantly more years of dancing and number of weekly pointe hours than those with no pathology on US imaging. No significant differences between the groups were identified for the rest of the variables. Dancing years were moderately correlated with AT thickness.ConclusionsAsymptomatic classic dancers had a high incidence of tendon pathology. Increased dancing years was associated with pathology in the AT. Nevertheless, these abnormalities may not affect dance performance.