背景: 旋轉，為芭蕾舞一個重要的動作。有許多因素會影響旋轉的動作控制，像是舞者的技巧程度、慣用腳或非慣用腳、準備位置寬度(準備時的雙足最短距離)。目前為止，並沒有完整的文獻報導有關於芭蕾舞旋轉與其相關影響的因子。所以完整量化芭蕾舞旋轉的動作控制，以及探討舞者的技巧程度、慣用腳或非慣用腳、準備位置寬度時對芭蕾舞旋轉動作的影響是必要的。
目的:比較單圈芭蕾舞向外旋轉的動作控制。此研究的特定目的如下：(1) 探討有經驗芭蕾舞者與初學者的動作控制差異。 (2) 比較慣用腳支撐與非慣用腳支撐執行芭蕾單圈旋轉的差異。 (3) 評估不同準備位置寬度對於單圈旋轉的影響。
方法: 本實驗受測者包括十三位有經驗的女性舞者與十三位初學女性舞者。所有受測者皆執行慣用腳支撐與非慣用腳支撐之單圈向外旋轉，並執行四種不同準備寬度之旋轉（包含自選寬度、0.5倍足長、1.0倍足長、1.5倍足長）。可將整個單圈芭蕾旋轉分成五個時期：準備期、雙腳支撐旋轉期、單腳支撐旋轉前期、單 腳支撐旋轉中期、結束期。本實驗會紀錄雙腳支撐旋轉期的上推力量(push force)，以及單腳支撐旋轉中期與結束期時的著地力量(landing force)。本實驗也會計算單腳支撐旋轉前期的旋轉軸與垂直軸之夾角(inclination angle of instantaneous screw axis)，和結束期的身體軀幹軸與垂直軸之夾角(trunk inclination angle)。同時，本實驗也會計算旋轉時的角速度(angular velocity)與支撐腳位移量(foot displacement)。
結果: (1) 有經驗舞者比初學舞者有較小的旋轉軸角度、旋轉角速度、和上推力量與著地力量。 (2) 有經驗舞者在慣用腳支撐比非慣用腳支撐旋轉時，有較小的旋轉軸角度和支撐腳位移量；初學舞者則在慣用腳支撐與非慣用腳支撐旋轉時，在旋轉軸角和支撐腳位移量是沒有差異的。 (3) 有經驗舞者在自選準備寬度旋轉時有最小的旋轉軸角度；初學舞者則是在0.5倍足長為準備位置寬度時有最小的支撐腳位移量。
結論: (1) 有經驗舞者在單圈旋轉表現比初學舞者佳。而初學舞者在準備時期會花較久的時間，卻在旋轉期時表現倉促。 (2) 有經驗舞者在慣用腳支撐單圈旋轉時，表現比非慣用腳支撐時好。初學舞者則在慣用腳支撐或非慣用腳支撐執行單圈旋轉表現，沒有顯著性的差異。 (3) 有經驗舞者在自選準備寬度旋轉時表現比其他準備寬度好;而初學舞者則是在0.5倍足長為準備寬度旋轉時表現最好。

Background: Turning, whole body rotation, is a fundamental movement in ballet. Several factors may be influential on the performance of the ballet turns, such as skill levels, leg-dominance, and preparatory distance (the distance between feet in the sagittal plane). To date, few complete motion analysis of ballet turning as well as factors which may affect the performance of ballet turning is reported in the literature. Therefore, it is necessary to evaluate the influences from skill levels, leg-dominance, and preparatory distances on ballet performance.
Purpose: To evaluate the postural control while performing single-revolution ballet turn with en dehors. The specific aims of the study were: (1) to investigate the postural control between the experienced dancers and novice dancers; (2) to investigate the difference between dominant leg (D) and non-dominant leg (ND) in both E and N groups; and (3) to evaluate the differences among different preparatory distance of turning in both E and N groups.
Methods: Thirteen female experienced dancers and thirteen female novice dancers participated in this study. Participants randomly performed ballet turning with en dehors in both D and ND leg support and four preparatory distances (self-selected (PDss), 0.5-fold of foot length (PD05), 1.0-fold of foot length (PD10), and 1.5-fold of foot length (PD15)). There were five phases in whole turning task: preparatory (PRE), turning with double-leg support (TDS), turning with single-leg support in pre-swing (TSSp), turning with single-leg support in mid-swing (TSSm), and ending (END) phases. The push force of gesture and supporting leg in TDS phase, and landing force in TSSm and END phases were measured. The inclination angle of instantaneous screw axis during TSSp and trunk inclination angle during END phase were calculated. The angular velocity on retire position and foot displacement of supporting leg during whole task were also detected.
Results: The experienced dancers had less inclination angle of instantaneous screw axis, angular velocity, push force and landing force than novice dancers. The experienced dancers also had less inclination angle of instantaneous screw axis and foot displacement with D leg support than that of ND leg support. On the other hand, the novice dancers had no difference in inclination angle of instantaneous screw axis and foot displacement between D and ND leg supports. The experienced dancers had smallest inclination angle of instantaneous screw axis in PDss compared to other preparatory distances. In addition, the novice dancers had smallest foot displacement in PD05 compared to other preparatory distances.
Conclusions: The experienced dancers had better performance than novice dancers. The novice group had longer duration in preparatory phase but shorter duration in turning phase. The experienced dancers had better ability in turning with D leg support, whereas the novice dancers had no preference of performance in turning for any side of leg. The experienced dancers had best performance with self-selected preparatory distance, whereas the novice dancers had best performance with 0.5-fold of foot length of preparatory distance.

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