Kinematic analysis of the gait in professional ballet dancers

Background: A ballet dance routine places extreme functional demands on the musculoskeletal system and affects the motor behaviour of the dancers. An extreme ballet position places high stress on many segments of the dancer's body and can significantly influence the mobility of the lower limb joints. Objective: The aim of this study was to observe the differences in the gait pattern between ballet dancers and non-dancers. Methods: Thirteen professional ballet dancers (5 males, 8 females; age 24.1 +/- 3.8 years; height 170.2 +/- 8.5 cm; weight 58.3 +/- 11.2 kg) participated in this research. We compared these subjects with twelve controls (3 males, 9 females; mean age 24.3 +/- 2.75 years; height 173.3 +/- 6.01 cm; weight 72.2 +/- 12.73 kg). None of the participants had any history of serious musculoskeletal pathology or injury or surgery in the lower limbs. Control group had no ballet experience. Each participant performed five trials of the gait at self-selected walking speed. Kinematic data was obtained using the Vicon MX optoelectronic system. The observed data was processed in the Vicon Nexus and Vicon Polygon programmes and statistically evaluated in Statistica. Non-parametric test (Mann-Whitney U test, p <.05) was applied for comparing the dancers and the controls. Results: Significant differences (p <.05) were found in all lower limb joints. In the dancers, greater hip extension (-15.30 +/- 3.31 degrees vs.-12.95 +/- 6.04 degrees; p =.008) and hip abduction (-9.18 +/- 5.89 degrees vs. -6.08 +/- 2.52 degrees; p <.001) peaks together with increased pelvic tilt (3.33 +/- 1.26 degrees vs. 3.01 +/- 1.46 degrees; p =.020), pelvic obliquity (12.46 +/- 3.05 degrees vs. 10.34 +/- 3.49 degrees; p <.001) and pelvic rotation (14.29 +/- 3.77 degrees vs. 13.26 +/- 4.91 degrees; p =.029) were observed. Additionally, the dancers demonstrated greater knee flexion (65.67 +/- 4.65 degrees vs. 62.45 +/- 5.24 degrees; p = .002) and knee extension (3.80 +/- 4.02 degrees vs.-1.54 +/- 5.65 degrees; p <.001) peaks during the swing phase when compared to the controls. Decreased maximal ankle plantar flexion was observed during the loading response (-8.84 +/- 3.74 degrees vs. -10.50 +/- 3.99 degrees) and increased maximal ankle plantar flexion in terminal stance (-20.30 +/- 4.93 degrees vs.-17.00 +/- 3.99 degrees; p =.025) was observed for the dancers. Conclusion: The results confirm that long-term intensive ballet training affects the kinematic pattern of particular joints during gait performance. The findings suggest overloading in the lumbosacral region and dysfunction or weakness of several muscles in ballet dancers.