Ballet Dancers at Low Risk for Anterior Cruciate Ligament InjuryStudies show that athletes involved in noncontact jumping sports have the highest rate of anterior cruciate ligament (ACL) injuries. The main mechanism of injury is called plant-and-cut maneuvers. There is too much load on the knee with the foot planted on the ground while the player changes direction quickly.
Since athletes in jumping sports seem to be at greatest risk for ACL injury, these researchers studied highly trained ballet and modern dancers. They suspected that with all the jumping and balance training involved in dance training, dancers might have a lower incidence of ACL injuries.
It turns out that elite dancers had far fewer ACL injuries compared to athletes involved in jumping activities. And, in particular, ballet dancers had a much lower risk of ACL injury compared to modern dancers. Female modern dancers were 13 times more likely to injure themselves compared to male modern dancers.
Why the differences? That's what this study explains. It seems that ballet dancers perform more than 200 jumps in a daily 90-minute technique class. The rigorous training is enough to prevent ACL injuries. This is true even though load on the knee during jump landings in dance can put up to 12 times the dancer's body weight in force on the knee joint.
They found this out by studying almost 300 dancers from four New York City area dance groups. Modern and ballet dancers between the ages of 18 and 41 were included. All dancers were followed for five years. Comparisons were made between athletes and dancers and between ballet and modern dancers. Measures taken for comparison included body mass index (BMI), Q-angle of the knee, muscle strength, and joint range-of-motion (hip and knee).
All new injuries were reported to the physical therapist or athletic trainer assigned to the dancer. All factors related to the injury were carefully collected and recorded. Time of day, season, and type of shoe or floor surface were reported. Dancer's mood (and for women, menstrual status) at the time of the injury was noted.
Time in training or performance was also reported throughout the five-year period. This was referred to as dance exposure. In the end, there were 12 ACL injuries among 298 dancers. Most (92 per cent) occurred when landing from a jump onto one leg.
Looking at all the variables, there was no evidence that race, gender, use of oral contraceptives (birth control pills) were linked with the injuries. Joint motion and strength differences were not able to explain differences between dancers with ACL injuries and noninjured dancers.
Most of the injuries occurred during a performance at the end of the season or late in the day after a long rehearsal. This finding suggests fatigue as a factor affecting neuromuscular control. The overall ACL injury rate for dancers was between 0.2 and 0.4 per cent. This is much lower than the range among other jumping athletes reported as being between one and eight per cent.
The authors offer several theories for the low rate of ACL injuries among dancers. First, dance training focuses on balance, alignment, footwork, and control. All of these skills may improve balance to a precise level needed to land single-leg jumps without injury. Second, dancers practice hundreds of jumps every day.
Third, jump practice progresses over time with supervision and guidance of an experienced dance instructor. And finally, unlike athletes, dancers practice the same steps in a routine. There are no surprise or unexpected movements to respond to. Rarely is contact with another dancer the cause of an ACL injury.
The higher rate of ACL injury among female modern dancers may be related to differences in postural and specific movements more typical among modern dancers. Modern dancers are more likely to make sudden changes in movement, speed, and direction. They are also involved in lifting other dancers, which is something ballerinas don't do. The direction and angle of jumps is also different for modern dancers.
In summary, the low incidence of ACL injuries among dancers points to different training techniques between dancers and other athletes. A focus on alignment, posture, and balance may help reduce injuries in athletes involved in jumping activities. For dancers, monitoring fatigue and focusing more attention on reducing fatigue may be of benefit.
Marijeanne Liederbach, PhD, PT, ATC, CSCS, et al. Incidence of Anterior Cruciate Ligament Injuries Among Elite Ballet and Modern Dancers. A 5-Year Prospective Study. In The American Journal of Sports Medicine. September 2008. Vol. 36. No. 9. Pp. 1779-1788.
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