Lott Melanie B
Department of Physics and Astronomy, Denison University, Granville, Ohio, USA, Department of Physics and Astronomy, Denison University, 100 West College Street, Granville, Ohio 43023, USA;, Email:
J Dance Med Sci. 2019 Mar 15;23(1):17-25. doi: 10.12678/1089-313X.23.1.17.
Few studies have investigated how balance is maintained while the body rotates in an upright posture. Under the basic definition of balance, the body's center of mass (CoM) lies along a vertical line over the base of support (BoS); therefore, balance can be regained by moving the position of the CoM or the BoS. In a ballet pirouette, extreme movement of the BoS is aesthetically unacceptable; however, subtler BoS translations may be a viable strategy for balance maintenance. The results of this study suggest that translation of the BoS is not only utilized but correlated with a larger number of revolutions, , in a pirouette. Although increasing is not the primary goal of the pirouette, scientific understanding of how dancers maintain balance while performing large turns can help dance educators teach safer, more effective pirouettes of any . To investigate the relationship between the number of revolutions completed in a pirouette and 1. physical properties of the dancers, 2. how the pirouettes were initiated, 3. maximum deviations from equilibrium, and 4. movement of the BoS, this study determined whether was correlated with several relevant biomechanical parameters. Motion analysis of 11 skilled female dancers performing standard ballet pirouettes determined CoM and BoS kinematics. Six variables were computed from these data: initial topple angle from vertical (4.5° ± 2.0°), initial margin of stability (-4.4 ± 2.8 cm), initial spin rate (2.19 ± 0.37 rev/s), maximum topple angle (9.8° ± 6.8°), normalized BoS distance traveled per revolution (7.3% ± 3.3%), and dancer effective pendulum length (1.172 ± 0.023 m). A significant positive correlation was found between and normalized BoS distance traveled per revolution (r = .873, p < 0.001). No significant correlations were found between and any of the other five variables. When the foot rotates against the ground, as in a pirouette, friction is kinetic (lower coefficient of friction than no relative motion between surfaces), and body manipulations for balance maintenance lead to greater likelihood of BoS translation. These results suggest that dancers should be encouraged to make adjustments that could lead to subtle BoS translations during rotations. Given this new information, more research is needed to determine the best practices for teaching balance maintenance during rotations in dance.
很少有研究调查身体以直立姿势旋转时是如何保持平衡的。在平衡的基本定义下，身体的重心（CoM）位于支撑面（BoS）上方的垂直线上；因此，可以通过移动重心或支撑面的位置来恢复平衡。在芭蕾舞单脚尖旋转中，支撑面的剧烈移动在美学上是不可接受的；然而，支撑面更细微的移动可能是维持平衡的一种可行策略。这项研究的结果表明，支撑面的移动不仅被利用，而且与单脚尖旋转中更多的旋转次数相关。虽然增加旋转次数不是单脚尖旋转的主要目标，但科学地理解舞者在进行大幅度旋转时如何保持平衡，有助于舞蹈教育工作者教授更安全、更有效的任何类型的单脚尖旋转。为了研究单脚尖旋转中完成的旋转次数与1. 舞者的身体属性、2. 单脚尖旋转的起始方式、3. 与平衡的最大偏差以及4. 支撑面的移动之间的关系，本研究确定了旋转次数是否与几个相关的生物力学参数相关。对11名熟练的女性舞者进行标准芭蕾舞单脚尖旋转的运动分析，确定了重心和支撑面的运动学。从这些数据中计算出六个变量：相对于垂直方向的初始倾倒角度（4.5°±2.0°）、初始稳定裕度（-4.4±2.8厘米）、初始旋转速度（2.19±0.37转/秒）、最大倾倒角度（9.8°±6.8°）、每旋转一圈支撑面移动的归一化距离（7.3%±3.3%）以及舞者的有效摆长（1.172±0.023米）。发现旋转次数与每旋转一圈支撑面移动的归一化距离之间存在显著的正相关（r = 0.873，p < 0.001）。在旋转次数与其他五个变量中的任何一个之间均未发现显著相关性。当脚在地面上旋转时，如在单脚尖旋转中，摩擦力是动摩擦力（摩擦系数低于表面之间无相对运动时的摩擦系数），并且为维持平衡而对身体进行的操控会导致支撑面移动的可能性更大。这些结果表明，应该鼓励舞者在旋转过程中做出可能导致支撑面细微移动的调整。鉴于这一新信息，需要更多研究来确定在舞蹈旋转过程中教授平衡维持的最佳方法。
