(F-216) Do Experienced Dancers Alter Landing Kinematics During Split Leaps or Center Leaps After Fatigue?

Introduction:: Most injuries to dancers occur in the lower extremities, specifically in the foot and ankle region. The most common injuries include, but are not limited to, ankle and knee sprains, ankle impingement syndromes, and stress fractures. Numerous potential risk factors have been determined for dancer injuries such as anatomical posture and technical mistakes. The purpose of this study was to compare landing technique kinematics during specific jumps that are common in dance before and after fatigue.

Materials and Methods:: This project was approved by the Institutional Review Board at the University of Michigan (HUM00228431). Adolescent advanced level dancers were recruited who had at least 5 years of training and were actively rehearsing at least 7 hours per week. Thirty-seven retroreflective markers were placed on anatomical landmarks on the lower extremities and trunk following a Rizzoli body protocol and a 12-camera system was used for motion capture. Subjects completed three dominant leg split leaps (suat de chats) and three center leaps before and after a fatigue protocol. The fatigue protocol was conducted on a stationary bike and consisted of a two-minute warm up at 60 rpm, an additional 30 seconds at 60 rpm with added resistance, and then a maximum effort sprint with the added resistance for as long as possible (maximum of 2 minutes). Ankle, knee, and hip angles in all three axial directions, along with trunk flexion, lateral lean, and vertical ground reaction force were determined at the time of maximum knee flexion during landing using Visual 3D software. Shapiro-Wilk tests were performed to test for normality. If the data were normal, a paired t-test was used to determine significance. If the data were not normal, a nonparametric equivalent (Mann-WhitneyU) test was utilized to determine significance (p < 0.05).

Results, Conclusions, and Discussions:: Nine female dancers and one male dancer participated in this study (15.9 ± 0.3 years). Subjects had 11.7 ± 0.9 years in dance training and were currently training 22.4 ± 2.1 hours per week. Ankle eversion and external rotation along with knee flexion significantly increased during center leaps after the fatigue protocol. No metrics were significantly different during split leaps. (Figure 1)

Previous dance-related studies utilize non-dance motions to quantify fatigue such as stop jump tasks and single leg drop vertical jumps. With this study, we were able to compare landing metrics in a dance-centered jump that is common among all dancers. This provides insight to how dancers typically land on a daily basis and what potential injuries could occur. According to our results, most lower extremity kinematics did not change, indicating that dancers tend to keep their technique even when fatigued. However, the significant increase in ankle eversion and external rotation reported indicates that there could be a potential for ankle sprains among dancers when fatigued. Future studies should examine techniques to prevent increased ankle eversion and external rotation when fatigued.

Acknowledgements (Optional): : The authors would like to thank the dancers and parents for their participation in this study as well as Regina Arriola, Kenneth Oralde, and Ruchika Tadakala for assisting with data collection.

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