Zaferiou Antonia M, Flashner Henryk, Wilcox Rand R, McNitt-Gray Jill L
Department of Biomedical Engineering, University of Southern California, 3616 Trousdale Parkway, Los Angeles, CA 90089, USA.
Department of Aerospace and Mechanical Engineering, University of Southern California, OHE 430E, Los Angeles, CA 90089, USA.
J Biomech. 2017 Feb 8;52:130-139. doi: 10.1016/j.jbiomech.2016.12.017. Epub 2016 Dec 29.
The pirouette turn is often initiated in neutral and externally rotated hip positions by dancers. This provides an opportunity to investigate how dancers satisfy the same mechanical objectives at the whole-body level when using different leg kinematics. The purpose of this study was to compare lower extremity control strategies during the turn initiation phase of pirouettes performed with and without hip external rotation. Skilled dancers (n=5) performed pirouette turns with and without hip external rotation. Joint kinetics during turn initiation were determined for both legs using ground reaction forces (GRFs) and segment kinematics. Hip muscle activations were monitored using electromyography. Using probability-based statistical methods, variables were compared across turn conditions as a group and within-dancer. Despite differences in GRFs and impulse generation between turn conditions, at least 90% of each GRF was aligned with the respective leg plane. A majority of the net joint moments at the ankle, knee, and hip acted about an axis perpendicular to the leg plane. However, differences in shank alignment relative to the leg plane affected the distribution of the knee net joint moment when represented with respect to the shank versus the thigh. During the initiation of both turns, most participants used ankle plantar flexor moments, knee extensor moments, flexor and abductor moments at the push leg׳s hip, and extensor and abductor moments at the turn leg׳s hip. Representation of joint kinetics using multiple reference systems assisted in understanding control priorities.
舞者在进行单脚尖旋转时，通常会在髋关节处于中立位且外旋的状态下开始旋转。这为研究舞者在使用不同腿部运动学特征时如何在全身水平上实现相同的力学目标提供了契机。本研究的目的是比较在有和没有髋关节外旋的情况下进行单脚尖旋转起始阶段时下肢的控制策略。熟练的舞者（n = 5）分别在有和没有髋关节外旋的情况下进行单脚尖旋转。利用地面反作用力（GRFs）和节段运动学来确定旋转起始阶段双腿的关节动力学。使用肌电图监测髋部肌肉的激活情况。采用基于概率的统计方法，将不同旋转条件下的变量作为一个整体以及在舞者个体内部进行比较。尽管不同旋转条件下的GRFs和冲量产生存在差异，但每个GRF至少90%与相应的腿部平面对齐。踝关节、膝关节和髋关节处的大部分净关节力矩围绕垂直于腿部平面的轴起作用。然而，相对于腿部平面，小腿对齐方式的差异会影响以小腿与大腿为参照时膝关节净关节力矩的分布。在两种旋转的起始阶段，大多数参与者使用踝关节跖屈力矩、膝关节伸肌力矩、支撑腿髋关节处的屈肌和外展肌力矩以及旋转腿髋关节处的伸肌和外展肌力矩。使用多个参考系来表示关节动力学有助于理解控制优先级。
