The role of muscle function and pointe shoe characteristics in Arabesque movement among ballet dancers with non-specific low back pain.

This study aimed to investigate posterior chain muscle function and the influence of pointe shoes in ballet dancers with and without low back pain (LBP) in the Arabesque. Twenty-nine young professional ballet dancers (17 with LBP and 12 healthy controls) were recruited. Muscle strength and mechanical properties of the erector spinae and hamstrings were assessed. The displacement of centre of mass (COM) during Arabesque under different shoe conditions (R-class, Chacott, and own shoes) was measured with a motion capture system. The LBP group exhibited greater dynamic stiffness and decreased mechanical stress relaxation time in the lateral hamstring compared to the control group. During Arabesque, the LBP group demonstrated significantly greater anterior-posterior displacement of the COM and a larger percentage of time to achieve maximal trunk extension angle. The COM displacement in vertical and medial-lateral directions was smaller in the R-class than in their own shoes. LBP impacts muscle mechanical properties, particularly in the lateral hamstring. The compromised muscle function resulted in a longer time to spinal extension during Arabesque, signifying that reduced trunk control contributed to greater COM displacement. Hence, it is essential to emphasise that evaluating muscle properties and dynamic postural control is imperative for dancers experiencing LBP.

Obstructive Sleep Apnea Effects on Pulmonary and Respiratory Muscle Function of Obese Children and Adolescents: A Preliminary Study.

OBJECTIVE: Obstructive sleep apnea causes a marked decrease in lung volume and increases lung elasticity in obese adults. However, pulmonary and respiratory muscle function of obese children with obstructive sleep apnea who are more prone to develop airway obstruction than adults is less understood. This study aimed to determine the effects of obstructive sleep apnea on pulmonary and respiratory muscle function in obese children and adolescents compared to those without obstructive sleep apnea. MATERIAL AND METHODS: This cross-sectional study enrolled 12 obese children and adolescents with a known polysomnographic diagnosis of obstructive sleep apnea and 12 controls that were matched for age, gender, and body mass index. Pulmonary function, maximal inspiratory pressure, maximum voluntary ventilation, and anthropometric variables were measured. RESULTS Obese children and adolescents with obstructive sleep apnea exhibited significantly lower maximal mid-expiratory flow and displayed a forced expiratory flow at 50% and 75% of vital capacity (all P < .05) compared to the control group. However, there were no changes in other pulmonary function variables (all P > .05). Their maximal inspiratory pressure and maximum voluntary ventilation were lower than those of the controls, but this was not statistically significant (all P > .05). CONCLUSION: Obstructive sleep apnea did not change pulmonary and respiratory muscle function in obese children and adolescents. The special assessment should be warranted to identify a reduction in maximal mid-expiratory flow and forced expiratory flow at 50% and 75% of vital capacity observed in this population.