Injury, Strength, and Jumping in Professional Ballet

Jumping and landing activities are the most common mechanism of injury in professional ballet dancers. There is limited evidence, however, that has elucidated the moderators of load experienced when jumping and landing in ballet. This thesis aimed to describe injury epidemiology, establish reliable methods of assessing strength and jumping, and explore the factors that may influence lower extremity load during jump landings in professional ballet dancers. A five-year injury epidemiology study revealed an incidence of medical attention and time-loss injuries of ~3–4 and ~1 per 1000 h of exposure, respectively. The mechanism of injury was jumping and landing activities in ~30–40% of time loss injuries. A systematic review found limited evidence that ballet dancers demonstrate externally rotated lower extremities, extended lower extremities prior to landing, and ankle-dominant jumping strategies. Two methodological studies established the within- and between-session reliability of vertical ground reaction force (vGRF) across several maximal isometric force tests and three-dimensional ankle mechanics during landing in turnout and parallel foot positions. The reliability of vGRF during maximal isometric force tests across the squat, standing plantarflexion, and seated plantarflexion positions demonstrated excellent reliability (intraclass correlation coefficients (ICC): 0.92–1.00) and low variability (coefficient of variation (CV): 2.0–6.5%). Three-dimensional ankle mechanics demonstrated within- (ICC: 0.17–0.96; CV: 1.4¬–82.3%) and between-session (ICC: 0.02–0.98; CV:1.3–57.1%) reliability ranging from poor to excellent, with, ankle excursion, peak ankle angle, and jump height demonstrating the greatest ICC values (ICC: 0.65–0.96; CV: 1.4–57%). The final two studies investigated jump landings in professional ballet dancers. A linear discriminate analysis revealed that three-dimensional ankle mechanics could discriminate different ballet foot positions, such that jump landings in fourth and fifth positions required a greater range of motion and ankle joint power when compared to other foot positions. Lastly, two linear mixed-effects models indicated that peak ankle joint moments and vGRFs have poor associations with strength, ankle dorsiflexion range of motion, and three-dimensional ankle excursions (R2: 0.01–0.02). Sex, foot position, and individual variation are more appropriate factors to consider when assessing the load experienced at a joint or system level. This thesis provides a thorough insight into injury, strength, and jumping in professional ballet dancers. To that end, this thesis has identified burdensome injuries and their mechanisms in professional ballet dancers alongside practical and reliable strategies to measure the physical attributes that may moderate the load experienced by a dancer upon landing.