The incidence of anterior cruciate ligament injuries among dancers is much lower than that among team sport athletes and no clear gender disparity has been reported in the dance population. Although numerous studies have observed differences in lower extremity landing biomechanics between male and female athletes, there is currently little research examining the landing biomechanics of male and female dancers. Comparing landing biomechanics within this population may help explain the lower overall anterior cruciate ligament injury rates and the lack of gender disparity. Due to the fact that dancers receive jump-specific and balance-specific training from a very young age, we hypothesized that there would be no gender differences in drop-landing biomechanics in professional dancers. Controlled laboratory study. Kinematics and ground-reaction forces were recorded as 33 professional modern and ballet dancers (12 men and 21 women) performed single-legged drop landings from a 30-cm platform. Joint kinematics and kinetics were compared between genders. No gender differences in joint kinematics or kinetics were found during landings (multivariate analysis of variance: P = .490 and P = .175, respectively). A significant relationship was found between the age at which the dancers began training and the peak hip adduction angle during landing (r = .358, P = .041). In executing a 30-cm drop landing, male and female dancers exhibited similar landing strategies and avoided landing patterns previously associated with increased injury rates. Commonly reported biomechanical differences between men and women, as well as the gender disparity among athletes in the incidence of ACL injuries, may be the result of inadequate experience in proper balance and landing technique rather than intrinsic gender factors. Beginning jump-specific and balance-specific training at an early age may counteract the potentially harmful adaptations in landing biomechanics observed in female athletes after maturity.

The incidence of anterior cruciate ligament (ACL) injuries among dancers is much lower than among team sport athletes, and no clear disparity between sexes has been reported in the dance population. Although numerous studies have observed differences in landing biomechanics of the lower extremity between male and female team sport athletes, there is currently little research examining the landing biomechanics of male and female dancers and none comparing athletes to dancers. Comparing the landing biomechanics within these populations may help explain the lower overall ACL injury rates and lack of sex disparity. The purpose was to compare the effects of sex and group (dancer vs team sport athlete) on single-legged drop-landing biomechanics. The primary hypothesis was that female dancers would perform a drop-landing task without demonstrating typical sex-related risk factors associated with ACL injuries. A secondary hypothesis was that female team sport athletes would display typical ACL risk factors during the same task. Controlled laboratory study. Kinematics and kinetics were recorded as 40 elite modern and ballet dancers (20 men and 20 women) and 40 team sport athletes (20 men and 20 women) performed single-legged drop landings from a 30-cm platform. Joint kinematics and kinetics were compared between groups and sexes with a group-by-sex multivariate analysis of variance (MANOVA) followed by pairwise t tests. Dancers of both sexes and male team sport athletes landed similarly in terms of frontal-plane knee alignment, whereas female team sport athletes landed with a significantly greater peak knee valgus (P = .007). Female dancers were found to have a lower hip adduction torque than those of the other 3 groups (P = .003). Dancers (male and female) exhibited a lower trunk side flexion (P = .002) and lower trunk forward flexion (P = .032) compared with team sport athletes. In executing a 30-cm drop landing, female team sport athletes displayed a greater knee valgus than did the other 3 groups. Dancers exhibited better trunk stability than did athletes. These biomechanical findings may provide insight into the cause of the epidemiological differences in ACL injuries between dancers and athletes and the lack of a sex disparity within dancers.

After TKA, (2) if changes in adduction moment are related to static alignment and varus angle during gait 6 months and 1 year after TKA, and (3) if these changes in loading pattern are related to changes in Knee Society scores. Methods We performed gait analysis on 15 patients (17 TKAs) before surgery and 6 months and 1 year after TKA. Weightbearing radiographs were used to assess coronal plane knee alignment. Results TKA corrected static knee alignment from 2.2° (2.5°) varus to 3.5° (2.7°) valgus at 6 months. Peak varus angle during gait was reduced from 9.7° (6.5°) to 3.6° (5.8°) at 6 months and 5.2° (7.6°) at 1 year. Peak adduction moment was reduced to 85% of the preoperative level at 6 months but increased to 94% of the preoperative level at 1 year. We observed a correlation between the increase in dynamic varus angle and increase in adduction moment from the 6-month to 1-year followups. Conclusions TKA improves knee adduction moment at 6 months, but this effect is lost with time (1 year). Clinical Relevance Despite restoration of static knee alignment, knee adduction moment remains high presumably predisposing to medial polyethylene wear as noted by retrieval studies....

Orishimo, KF, Kremenic, IJ, Mullaney, MJ, Fukunaga, T, Serio, N, and McHugh, MP. Role of pelvis and trunk biomechanics in generating ball velocity in baseball pitching. J Strength Cond Res 37(3): 623–628, 2023—The purpose of this study was to determine the impact of pelvis rotation velocity, trunk rotation velocity, and hip-shoulder separation on ball velocity during baseball pitching. Fastball pitching kinematics were recorded in 29 male pitchers (age 17 ± 2 years, 23 high school, 6 college). Pelvis and trunk angular velocities and hip-shoulder separation were calculated and averaged for the 3 fastest pitches. Associations between peak pelvis velocity, peak trunk velocity, hip-shoulder separation at foot contact, and ball velocity were assessed using Pearson correlation coefficients and multiple regression. The average ball velocity was 33.5 ± 2.8 m·s⁻¹. The average hip-shoulder separation at foot contact was 50 ± 12°. The peak pelvis velocity (596 ± 88°·s⁻¹) occurred at 12 ± 11% of the time from stride foot contact to ball release, with the peak trunk velocity (959 ± 120°·s⁻¹) occurring at 36 ± 11%. Peak trunk velocity was predictive of ball velocity (p = 0.002), with 25% of the variability in ball velocity explained. No combination of factors further explained ball velocity. Hip-shoulder separation at foot contact (17%, p = 0.027), peak pelvis velocity (23%, p = 0.008), and the timing of peak pelvis velocity (16%, p = 0.031) individually predicted peak trunk velocity. The combination of peak pelvis velocity, hip-shoulder separation at foot contact, and the timing of peak trunk velocity explained 55% of the variability in trunk rotation velocity (p < 0.001). These data highlight the importance of interactions between pelvis and trunk for maximizing velocity in pitching. Training to improve pelvis-trunk axial dissociation may increase maximal trunk rotation velocity and thereby increase ball velocity without increasing training load on the shoulder and elbow.