A Comparison of Landing Mechanics Between Dancers and Team-Sport Athletes
Ian J. Kremenic1, Marshall Hagins2, Marijeanne Liederbach3, Karl F. Orishimo1, Evangelos Pappas2.
Purpose: The incidence of anterior cruciate ligament (ACL) injuries among dancers is much lower than among team-sport athletes, and no clear gender disparity has been reported in dancers. Additionally, fatigue is strongly- linked to increased risk of injury. The purpose of this study was to compare the effects of sex, group (dancer vs. team-sport athlete) and fatigue on single-leg drop-landing biomechanics.
Methods: Kinematics and kinetics were recorded as 40 elite modern and ballet dancers (20 men and 20 women) and 40 athletes (20 men and 20 women) performed single-legged drop landings from a 30-cm platform, before and after a fatigue protocol (step-ups and vertical jumps). Un-fatigued and fatigued joint kinematics and kinetics were compared between groups and genders using 3 separate MANOVAs according to three theories regarding ACL injury: ligament dominance, quadriceps dominance and trunk dominance.
Results: Dancers of both genders and male athletes landed similarly in terms of frontal plane knee alignment, whereas female athletes landed with greater peak knee valgus (p=0.007). Female dancers were found to have less hip adduction torque than the other three groups (p=0.003). Dancers (males and females) exhibited less trunk side flexion (p=0.002) and less trunk flexion (p=0.032) than athletes. Dancers took longer (p=0.023) than athletes to reach a similar state of fatigue. Multiple parameters of landing changed with fatigue, such that fatigued subjects landed with mechanics that were more at-risk for ACL injury as compared to prior to fatigue. However, there was no differential effect of fatigue on dancers vs. athletes.
Conclusions: In executing a 30-cm drop landing, female athletes displayed greater knee valgus than the other three groups. Dancers exhibited better trunk control than athletes. While dancers took longer to fatigue than athletes, fatigue changed landing mechanics similarly in both dancers and athletes, with all groups landing with worse alignment after fatigue. Female athletes had landing patterns associated with ACL injury risk when compared to the other three groups. These biomechanical findings may provide insight into the etiology of the epidemiological differences in ACL injury between dancers and athletes and the lack of a gender disparity within dancers.
1 Nicholas Institute of Sports Medicine and Athletic Trauma at Lenox Hill Hospital, New York, NY.
2 Long Island University, Brooklyn, NY.
3 NYU Langone Medical Center Hospital for Joint Diseases, New York, NY.
(Sponsor: Malachy McHugh, FACSM)