||The effect of fatigue on balance performance and movement control in ballet dancers
||Department of Physical Therapy
Continuous relative phase
方法：二十位年輕健康的女性舞者在疲勞誘發前和誘發後分別執行四種不同的舞蹈動作：開合小跳(petit echappe)、雙足站姿下墊腳(releve)、單腳支撐並升降重心(fondu)以及單腳靜止站立(retire)。動作過程中，八台紅外線攝影機和兩塊力板會分別記錄舞者的動作以及地面反作用力，且同時以肌電儀收取下肢的肌電訊號。此外，利用連續性相對相位分析法(continuous relative phase)及非控制域理論(uncontrolled manifold)分析舞者肢體協調的表現；連續性相對相位分析法量化下肢關節間協調性，利用關節位置與關節角速度求得關節間的相位偏差，較多的相位偏差代表關節間的相對運動較無一致性；非控制域理論將全身肢段的變異量切割為目標等同變異量和非目標等同變異量，其中目標等同變異量不會造成身體質量中心位置的改變，而非目標等同變異量則會造成身體質量中心位置的改變，探討肢段的變異量是否會對影響舞者控制身體質量中心的位置。隨後，使用配對樣本t檢定法比較疲勞前後是否有顯著差異。
Background and Purpose: Fatigue is an unavoidable phenomenon in athletes during their routine practice. The decreased ability of movement control after exhaustion may increase the risk of injury; for example, ballet dancers often suffer from lower extremity injury after long duration of performance or rehearsal. However, few studies evaluated the effect of fatigue on ballet dancers’ performance and control strategy. Thus, the aim of this study was to examine the effect of fatigue on the balance performance, movement performance, and movement control in the ballet dancers.
Methods: Twenty healthy female ballet dancers participated in this study and performed petit echappe, releve, fondu and retire before and after fatigue, respectively. A motion analysis system recorded three-dimensional videographic data and is also synchronized to two force plates to record the ground reaction force. The Delsys surface electromyography system (EMG) was used to detect the muscle activity of medial gastrocnemius, soleus, peroneus longus, tibialis anterior, rectus femoris, and hamstrings in data collection. In addition, continuous relative phase and uncontrolled manifold were used to analyze the movement pattern. Continuous relative phase (CRP) was used to evaluate the inter-joint coordination in dancers’ lower extremity. The lower deviation phase indicates a more consistent coordination pattern between two joints. Uncontrolled manifold (UCM) portions the segmental variability into two components; one component didn’t affect center of mass (COM) position, the other component led COM position changed. The paired-t test was used to detect the difference between pre-fatigue and post-fatigue with a significant level in 0.05.
Results: We found that the fatigue (1) reduced the jumping height or raising height; (2) decreased the muscle activity of antagonist but increased the muscle activity of agonist muscle with left shifted median frequency; (3) diminished the ground reaction force during landing; (4) increased displacement of center of mass or center of pressure with faster velocity in the anterior-posterior and medial-lateral directions; (5) increased the deviation phase between the joints of lower limbs; (6) increased the variability in both UCM components, especially in the parallel UCM component.
Conclusions: Fatigue changed the dancers’ movement pattern and impaired their performance. Poor balance ability and unstable movement control observed in our ballet dancers may increase the risk of injury. Furthermore, the greater movement variability also affected the dancing aesthetic. According to our findings, a proper training program, such as peroneal longus muscle training or neuromuscular control practice, to reduce or to delay the occurrence of fatigue is necessary for ballet dancers to enhance performance and to prevent dance-related injuries.
中文摘要(Chinese abstract) III
英文摘要(English abstract) V
目次 (Table of Content) X
表目錄(List of Table) XIII
圖目錄(List of Figure) XV
Chapter 1 Background 1
Chapter 2 Literature Review 3
2.1 Introduction of Ballet dance 3
2.1.1 Basic concepts in ballet 3
2.1.2 Motor control in ballet dancers 6
2.1.3 Epidemiology of ballet injury 8
2.2 Fatigue 10
2.2.1 The definition of fatigue 10
2.2.2 Physiology of neuromuscular fatigue 10
2.2.3 The potential risk of fatigue for athletes 12
2.3 Analysis for movement 13
2.3.1 Continuous relative phase angle (CRP) 14
2.3.2 Uncontrolled manifold (UCM) 15
2.4 Research purpose 17
2.5 Hypothesis 17
Chapter 3 Materials and Methods 19
3.1 Subjects 19
3.2 Instrumentations 19
3.3 Experimental procedure 22
3.3.1 Anthropometry measurement 23
3.3.2 Fatigue protocol 25
3.3.3 Data collection 29
3.4 Data reduction 32
3.4.1 Parameters 33
3.4.2 Analysis of human movement 36
3.4.3 Phase definition 43
3.4.4 Dependent variable 44
3.5 Statistical analysis 47
Chapter 4 Result 48
4.1 Basic data 48
4.2 Petit Echappe 48
4.2.1 Temporal parameters 49
4.2.2 Kinematic parameters 50
4.2.3 Kinetic parameters 54
4.2.4 EMG parameters 57
4.3 Releve 63
4.3.1 Temporal parameters 63
4.3.2 Kinematic parameters 63
4.3.3 EMG parameters 68
4.4 Battenment Fondu 72
4.4.1 Temporal parameters 72
4.4.2 Kinematic parameters 72
4.4.3 Kinetic parameters 78
4.4.4 EMG parameters 79
4.5 Retiré 83
4.5.1 Kinematic parameters 83
4.5.2 Kinetic parameters 85
4.5.3 EMG parameters 87
4.6 Analysis of human movement 92
4.6.1 Continuous relative phase 92
4.6.2 Uncontrolled manifold 104
Chapter 5 Discussion 116
5.1 Petit Echappe 116
5.1.1 Temporal parameters 116
5.1.2 Kinematic parameters 118
5.1.3 Kinetic parameters 123
5.1.4 EMG parameters 127
5.2 Releve 131
5.2.1 Temporal parameters 131
5.2.2 Kinematic parameters 131
5.2.3 EMG parameters 134
5.3 Battenment Fondu 137
5.3.1 Temporal parameters 137
5.3.2 Kinematic parameters 137
5.3.3 Kinetic parameters 141
5.3.4 EMG parameters 141
5.4 Retire 143
5.4.1 Kinematic parameters 143
5.4.2 Kinetic parameters 144
5.4.3 EMG parameters 145
5.5 Analysis of human movement 146
5.5.1 Continuous relative phase 147
5.5.2 Uncontrolled manifold 155
5.6 Limitation 159
Chapter 6 Conclusion 161
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