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C. Kaneko1, M. Anan1
1Oita University, Graduate School of Welfare and Health Science, Oita, Japan
Background: In the classic ballet, toe standing is frequently performed and requires a higher balance ability. In addition, an injury due to the overuse of the lower back and legs has been reported to often occur in classic ballet, and the incidence of an injury is higher in females than in males. However, few studies have clarified whether a sex-related difference in toe-standing balance ability exists.
Purpose: We aimed to determine the difference in balance control between males and females while toe standing by comparing the behavior of the center of mass (COM) and each segment angle and joint moment.
Methods: The subjects were 20 healthy people (13 men and 7 women, 21.1 ± 1.3 years old). We attached 47 infrared markers with a diameter of 14 mm to the body landmarks in each subject. We performed measurements using a three-dimensional motion analysis system (Vicon) consisting of 10 infrared cameras at a sampling frequency of 100 Hz, and obtained marker coordinates. To obtain floor reaction force data, we used two force plates and performed measurements at a sampling frequency of 1000 Hz.
The task motion was toe standing for 30 s, with both hip joints rotated 45° externally. The position of the upper limb was measured by enhaut, which is one of the basic ballet positions. The task motion was maintained for 30 s from the standing posture and was performed twice. The total length (LNG) of the COM, coefficient of variation (CV) of each segment angle, and joint moment were calculated based on marker coordinates and force plate data. The most stable duration of 10 s of the obtained data was set as the analysis interval. For statistical analysis, statistical software was used to perform a two-sample t test for data with normal distributions, and a Mann-Whitney U test, when no normality was observed. The significance level was <5%.
The task motion was toe standing for 30 s, with both hip joints rotated 45° externally. The position of the upper limb was measured by enhaut, which is one of the basic ballet positions. The task motion was maintained for 30 s from the standing posture and was performed twice. The total length (LNG) of the COM, coefficient of variation (CV) of each segment angle, and joint moment were calculated based on marker coordinates and force plate data. The most stable duration of 10 s of the obtained data was set as the analysis interval. For statistical analysis, statistical software was used to perform a two-sample t test for data with normal distributions, and a Mann-Whitney U test, when no normality was observed. The significance level was <5%.
Results: The LNG of the COM was 76.3 ± 13.9 mm in men and 74.4 ± 22.9 mm in women, and was not significantly different between the sex groups. On the other hand, the CV of the thoracic segment angle was 2.9 ± 2.1 in men and 31.1 ± 27.1 women, with a significant difference between the groups. Joint moments did not differ significantly between the two groups, but 7 men showed a lumbar flexion moment during toe standing, and 5 women showed a lumbar extension moment.
Conclusion(s): Incorrect toe-standing posture has been reported to be one of the causes of an injury in ballet dancers. Females maintain stability by moving the thorax segment more during toe standing and tend to control the thorax segment by lumbar extension moments. Previous studies showed that people with chronic low back pain have greater lumbar extension moments. The findings suggest that postural control during toe standing increases the load on the lumbar region in females.
Implications: These findings suggest that the physical therapy approach to decrease the variation of the thoracic segment during toe standing might be effective for women with low back pain.
Funding, acknowledgements: This study was supported by Presidential Strategic Grant in Oita University.
Keywords: toe-standing, coefficient of variation, low back pain
Topic: Musculoskeletal
Did this work require ethics approval? Yes
Institution: The Faculty of Welfare and Health Science, Oita University
Committee: The Ethics Committee of the Faculty of Welfare and Health Science
Ethics number: F17006
All authors, affiliations and abstracts have been published as submitted.
