Lower extremity control during turns initiated with and without hip external rotation

Area of Science:

• Dance biomechanics
• Human movement analysis
• Sports science

Background:

• Pirouette turns in dance are often initiated from neutral or externally rotated hip positions.
• Understanding how dancers achieve consistent mechanical objectives with varying leg kinematics is crucial for injury prevention and performance enhancement.

Purpose of the Study:

• To compare lower extremity control strategies during pirouette turn initiation.
• To investigate differences in joint kinetics and muscle activation between pirouettes performed with and without hip external rotation.

Main Methods:

• Five skilled dancers performed pirouette turns under two conditions: with and without hip external rotation.
• Ground reaction forces (GRFs), segment kinematics, and hip muscle activations (electromyography) were recorded.
• Probability-based statistical methods were used for group and within-dancer comparisons.

Main Results:

• Despite variations in GRFs and impulse generation, over 90% of GRF aligned with the leg plane in both conditions.
• Most net joint moments at the ankle, knee, and hip acted perpendicular to the leg plane.
• Shank alignment influenced knee moment distribution, highlighting the importance of reference frame selection.

Conclusions:

• Dancers employ consistent whole-body mechanical strategies for pirouette initiation, regardless of initial hip external rotation.
• Lower extremity joint moments are primarily directed to achieve turn objectives.
• Using multiple reference systems aids in understanding complex joint control strategies in dance.