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Sensors (Basel) ; 20(3)2020 Jan 29.
Artigo em Inglês | MEDLINE | ID: mdl-32013212


This study aimed to develop a wearable sensor system, using machine-learning models, capable of accurately estimating peak ground reaction force (GRF) during ballet jumps in the field. Female dancers (n = 30) performed a series of bilateral and unilateral ballet jumps. Dancers wore six ActiGraph Link wearable sensors (100 Hz). Data were collected simultaneously from two AMTI force platforms and synchronised with the ActiGraph data. Due to sensor hardware malfunctions and synchronisation issues, a multistage approach to model development, using a reduced data set, was taken. Using data from the 14 dancers with complete multi-sensor synchronised data, the best single sensor was determined. Subsequently, the best single sensor model was refined and validated using all available data for that sensor (23 dancers). Root mean square error (RMSE) in body weight (BW) and correlation coefficients (r) were used to assess the GRF profile, and Bland-Altman plots were used to assess model peak GRF accuracy. The model based on sacrum data was the most accurate single sensor model (unilateral landings: RMSE = 0.24 BW, r = 0.95; bilateral landings: RMSE = 0.21 BW, r = 0.98) with the refined model still showing good accuracy (unilateral: RMSE = 0.42 BW, r = 0.80; bilateral: RMSE = 0.39 BW, r = 0.92). Machine-learning models applied to wearable sensor data can provide a field-based system for GRF estimation during ballet jumps.

Med Probl Perform Art ; 34(3): 147-153, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31482173


OBJECTIVE: Low back pain (LBP) is common in dancers. A biopsychosocial model should be considered in the aetiology of LBP, including a dancer's general beliefs of the low back and movements of the spine. This study aimed to determine pre-professional dancers' beliefs about their lower back in general and dance-specific movements of the spine and to explore whether these beliefs were influenced by a history of disabling LBP. METHODS: 52 pre-professional female dancers (mean age 18.3 [1.4] yrs) were recruited and reported whether they had a history of disabling LBP and completed the Back Pain Attitudes Questionnaire (Back-PAQ) and a dance movement beliefs questionnaire. A linear mixed model was applied to determine the effect of a history of disabling LBP on dancers' beliefs (p<0.05). RESULTS: 20 dancers reported a history of disabling LBP. Regardless of this LBP history, dancers held generally negative beliefs as measured by the Back-PAQ (p=0.130). A history of disabling LBP did not influence dancers' perceived movement safety of all tasks (p=0.867), and dancers held negative beliefs towards extension activities. These beliefs were linked to the conceptions of perceived risk of damage and the need to protect the lower back. CONCLUSIONS: Dancers hold negative general beliefs around the low back and low back movements, regardless of a history of disabling LBP. Dancers perceive extension activities as more dangerous than flexion activities. These beliefs may reflect a combination of pain experience and beliefs specific to dance.

Dança , Dor Lombar , Adulto , Dança/lesões , Feminino , Humanos , Movimento , Amplitude de Movimento Articular , Inquéritos e Questionários , Adulto Jovem
J Dance Med Sci ; 23(2): 72-79, 2019 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-31122316


The high prevalence of lower limb overuse injuries among adolescent ballet dancers may be due in part to repetitive land- ings. This cross-sectional study compared how adolescent ballet dancers perform a drop-landing task in comparison to non-dancers in order to help understand injury mechanics. Fifteen adolescent female ballet dancers aged 11.9 ± 1.1 years and 17 non-dancers aged 10.9 ± 0.9 years each performed three single limb drop-landings from a 30 cm box. An 18-camera motion capture system (Vicon MX; Oxford Metrics, Oxford, UK; 250 Hz) and a force platform (Advanced Mechanical Technology Inc., Watertown, Massachusetts, USA; 2,000 Hz) were used to collect lower limb joint angles in all three planes of motion and peak vertical ground reaction forces during the landing phase. These variables were compared for the two sets of participants using independent samples t-tests (p < 0.01). While the dancers landed with greater sagittal plane range of motion, this appeared to provide no mechanical advantage with no reduction in ground reaction force. Rather, the increased sagittal range of motion was coupled with increased coronal and frontal plane motion. This may place dancers at increased risk of injury.

Articulação do Tornozelo/fisiologia , Dança/fisiologia , Articulação do Quadril/fisiologia , Articulação do Joelho/fisiologia , Adolescente , Fenômenos Biomecânicos , Criança , Estudos Transversais , Teste de Esforço , Feminino , Humanos
Phys Ther Sport ; 32: 180-186, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-29800796


OBJECTIVES: To 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. DESIGN: Cross-sectional. SETTING: Laboratory. PARTICIPANTS: Thirteen adolescent female ballet dancers (11.8 ±â€¯1.1 years) and 17 non-dancers (10.9 ±â€¯0.8 years) performed hop and stop jump tasks. MAIN OUTCOME MEASURES: Vertical ground reaction force, and three-dimensional ankle, knee and hip joint angles and moments during the landing phase. RESULTS: Dancers 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. CONCLUSIONS: Adolescent 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.

Dança/fisiologia , Extremidade Inferior/fisiologia , Adolescente , Articulação do Tornozelo , Fenômenos Biomecânicos , Criança , Estudos Transversais , Feminino , Articulação do Quadril , Humanos , Articulação do Joelho