芭蕾是一種容易受傷的專業技術。在所有與芭蕾相關的傷害中，腳踝與足部的傷害就佔了35%~55%。舞者或許有良好的單腳站平衡能力，但是在所需的芭蕾舞特殊技巧平衡上卻沒有令人滿意的表現。肌電圖可能可以幫助我們解釋舞者的平衡能力或是受傷模式。因此本篇研究的目的是(1).決定平衡能力與之前受傷史的關係，若有關係，哪些下肢肌肉活動度與此關係有關聯。(2).決定跳躍動作的模式與之前受傷史的關係。
本實驗徵召了22個芭蕾女大學生，舞者在過去一年內下肢有與執行芭蕾動作相關所造成的受傷被分到BI組，過去一年內沒受傷者則被分到BU組，各11位。另徵召了11個年齡相符的正常受試者為控制組(C)。測試內容包括單腳站眼睛睜開、單腳站眼睛閉起來、古典芭蕾的基本動作一位和五位(Basic Position One and Five)、腳尖點地(Pointé), 分腿跳(Sissonné Ferméé) 以及鶴立式舞姿(Attitudé)。實驗器材包括反光球、肌電圖、以及力板。
結果顯示相較於BU組和C組而言，BI組的平衡控制能力是比較差的。這些BI組的舞者都有腳踝扭傷的受傷史，這可能導致他們本體覺的缺損進而造成較差的內外側穩定度。然而，單腳站的肌電圖結果卻是顯示在C組和舞者間才有差異。我們推測BI組舞者可能是使用髖部策略去代償腳踝的不穩定。執行基本動作五位時，我們發現BI組的壓力中心在內外側有不穩定的情形，這可能是因為害怕使用曾經受傷過的優勢腳，並活化非優勢腳的前脛肌來代償。BI組在執行腳尖點地時，其壓力中心的位移範圍在任一方向都比BU組來的大。BI組使用較多的肌肉活動度，包括兩側的前脛肌和髖內收肌，去穩定極度腳踝蹠屈的姿勢，這暗示著腳踝內翻受傷的危險性和髖關節的不穩定。
在分腿跳的執行終期(terminal phase)，BI組的舞者有比較小的後足相對於脛骨(hindfoot to tibia)的外展角度、以及比較小的負荷率(loading rate)。在上升期(rising phase)，BI組著重在抬起前腳且忽略後腳的穩定度，這可能會造成BI組比BU組還要不穩定的原因。鶴立式舞姿則是由於個人執行的差異度導致結果一致性很差。
總結，我們發現舞者的腳踝受傷史與內外側平衡能力有高度相關，我們建議舞者應該要根據特定的芭蕾舞動作進行肌肉和平衡控制訓練。未來進一步的研究是要決定訓練計劃如何影響受傷率。

Ballet is a vulnerable expertise and the ankle and foot injuries constitute 35~55% of ballet injuries. Some ballet dancers may be good at unilateral balance tests but exhibit unsatisfactory control of balance in ballet choreography. The electromyography (EMG) may explain the ability of balance control or injury pattern in ballet dancers. The purposes of this study centered on two topics: (1) to determine whether the balance ability was related to the previous injuries and if the relationship was found, which lower extremity muscle activity was associated with this relationship; (2) to determine whether the movement pattern of jump landing was related to the previous injuries.
Twenty-two college ballet students and eleven normal healthy age matched subjects as a control group (C) were recruited for this study. The ballet students were divided into BI group (n=11) and BU group (n=11). The injury criteria were the dancers suffered from one or more lower extremity injuries related to the ballet in the past year. The tasks tested included unilateral balance tests with eye open or eye close, Basic Position One and Five, Pointé, Sissonné Ferméé and Attitudé. The instruments were the Motion Analysis system, MA300 electromyography system and Kistler force plate.
The BI dancers had poor balance control compared with the BU dancers and control group in our study. Those BI dancers all suffered from ankle sprain which may result in impaired somatosensory and thus poor stability in medial-lateral direction. However, the EMG difference was only found between control group and ballet subjects during single leg standing trials. The BI subjects might use the hip strategy to compensate the instability of ankle joints. In Basic Position Five, we found the unsteadiness of COP in medial-lateral direction may be due to the fear of using dominant leg and compensated with the firing of ND.TA in BI groups. BI dancers also exhibited greater moving range of COP position in either direction compared with BU dancers during Pointé with arm forward. Compared with the BU subjects, the BI subjects employed greater muscle effort of both TA and ADD to stabilize the extreme ankle plantarflxion position which suggested the risk of ankle inversion injury due to the TA muscle and the instability of hip joint due to the ADD muscle.
BI dancers exhibited smaller angle of hindfoot to tibia abduction, and smaller loading rate in the terminal phase during Sissonné Ferméé. During rising phase, BI subjects focused on the raising of the front leg and ignored the stabilization of the rear leg which may cause instability more easily compared with the BU subjects. The investigation of Attitudé movement didn’t have specific findings which may suggest the variation of execution in Attitudé.
In conclusion, we found the highly correlated relationships between the ankle injury history and medial-lateral balance ability. We suggest that the muscle strengthening and balance control training for specific ballet movements may be necessary for ballet dancers. Further research was needed to determine how the training program affects the injury rate.

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