Photographed by Lauren Perlstein.
“Knees over your toes” is one of the most common phrases I’ve heard in a lifetime of training as a dancer. It’s how teachers remind students to maintain neutral alignment during knee bends, to prevent caving in or buckling out. Today, in my dual career as a personal trainer and dancer, I find myself repeating this mantra to my clients all the time during squats and lunges. Now, science is stepping in to back me up.
According to researchers at the Harkness Center for Dance Injuries, part of NYU Langone Medical Center, “landing like a dancer” may be the key to preventing painful knee injuries. In a previous study conducted over a five-year period, Harkness Center researchers discovered that modern and ballet dancers experience a much lower incidence of injuries to the ACL (one of the knee's major stabilizing ligaments) than team-sport athletes do. And, they experience this lower injury rate despite the fact that dancers regularly jump more than 200 times in just one class. So, how are dancers protecting their ACLs in spite of it all?
A pair of new studies from the Harkness Center (published earlier this year in The American Journal of Sports Medicine) takes a closer look at what makes dancers’ landings different. The research team looked at four groups: male dancers, female dancers, male team-sport athletes, and female team-sport athletes. The participants were asked to stand on one leg, jump off a 30-cm platform, and land on that same leg. They were closely monitored with biomechanical instruments to see if they hit risky landing positions known to lead to ACL injury — such as knee valgus (when the knees fall in toward the midline) or trunk instability (when the torso falls forward, backward, or to one side upon landing).
What the researchers found was that of the four test groups, female dancers had the best torso stability of all, while female athletes demonstrated risk factors for ACL injury more frequently than any of the other groups. In fact, women athletes are three to eight times more likely to suffer ACL injuries than their male counterparts, say the Harkness Center researchers. But, the study showed no ACL-injury disparity between male and female dancers.
"Every injury," says Marijeanne Liederbach, PhD, PT, director of research and education at the Harkness Center, "is the result of a complex interplay between the intrinsic (meaning the internal attributes and state of the athlete) and extrinsic variables (like footwear, the playing surface, other players...and other factors in the environment).”
Photographed by Lauren Perlstein.
ACL injuries are tough to recover from, often require surgery, and can increase the risk of developing arthritis in the injured knee, according to the American Academy of Orthopaedic Surgeons. Dr. Liederbach notes that there are about 200,000 ACL injuries in the U.S. every year, and that sports medicine specialists have come to see them as an "epidemic." Most of these are non-contact injuries, meaning they don't involve collision with another athlete. They most often occur in sports that involve frequent jumping and quick changes of direction — think basketball, soccer, volleyball, and lacrosse. But, high-impact workouts such as CrossFit, boot camp, and obstacle-course races may produce similar risks. These high-intensity classes are great for burning fat, building muscle, and increasing your strength. But, if you’re incorporating jumps into your fitness routine, remember: What goes up must come down.
In previous studies, the Harkness Center team found that ACL injuries most often occurred toward the end of the day or the end of a season, suggesting that fatigue is a factor. In part two of their most recent study, researchers put this theory to the test by having subjects perform the same single-leg landings after completing a fatigue protocol of step-ups and jumps. Participants had to repeat these exercises until their maximum vertical-jump height decreased by 10% — a marker of fatigue.
All groups in the study showed worse landing technique when fatigued. But, the dancers took much longer to reach fatigue than athletes did — 40% longer. “We think this is because dancers do such a high volume of jumps per day as part of their regular training,” says Dr. Liederbach. “And, the demands in their environment are for the jumps to be virtuosic and perfect in technique. So, this is ingrained in these artistic athletes from a very young age, and is watched with a high level of scrutiny on a daily basis.”
That's right: The aesthetic consciousness of dance training may lead to safer landings. Dancers are taught to maintain neutral, stable alignment of the knees, hips, and torso when landing from jumps. It makes sense from a physiological standpoint, but it also looks good on stage. Plus, dancers utilize a large range of motion at their ankle joint (a toe-to-heel landing) when completing jumps, which could play a role in preventing non-contact ACL injury.
“Dancers’ landing time is longer, and they're trained to land softly and to go through that whole limb-range of motion in a coordinated fashion,” explains Dr. Liederbach. “The potential to absorb shock through that method is substantial, and something we may be able to help athletes with. We think it’s an issue of deceleration during the landing.”
So, how can you land more like a dancer? The most obvious answer: Jump more, and land correctly. But, Dr. Liederbach warns that you might need to work your way there. Here's how to implement the training techniques that ballet dancers use — in your own workouts.
Photographed by Lauren Perlstein.
“It's just fantastic what plyometric (or jump) training will do for the body,” Dr. Liederbach says. “But, alignment should be job number-one.” You want to build up to proper technique. For example, before you start doing jumping switch-lunges, make sure you have mastered the basic reverse-and-forward lunge technique. If you want to try box jumps, start with the smallest box available and work your way up.
Now, for technique pointers: When you bend your knees, especially when landing from a jump — squat jumps, box jumps, jumping lunges, or even jumping jacks — follow my dance teachers’ “knees over toes” tip. Never let your knees fall in toward your midline or out to the sides. To do this, think of aiming your knees straight out over your second and third toe. The next checkpoint is your pelvis; if your hips are jutting out to one side, or if your lower back is arched and your butt is sticking out “belfie”-style, you’re doing it wrong. Here’s another dance-teacher tip: Think of your pelvis as a fishbowl. You want to keep it upright, so it doesn't spill.
The last thing to watch out for is stability of your torso. According to Dr. Liederbach, poor control of the torso, especially a side lean during landing, is one of the biggest risk factors for ACL injury. Engage the muscles of your core to keep your back long and upright when you land. In two-legged landings, make sure one leg isn’t doing all the work. Many of us have a tendency to rely more on our dominant side to absorb the impact of landing. You should be placing equal weight on both legs; a mirror can really help with this.
Finally, the stronger your feet, ankles, calves, thighs, and hips are, the more control you’ll have over your landings — so try incorporating more balance exercises into your workouts, using tools like Bosu balls and balance boards. Your hip muscles also play an important stabilizing role in single-leg balances. To strengthen this area, try exercises like tube walks (mini side-steps with a resistance band or loop around the ankles), or side-lying leg raises. And, adding some calf raises to your gym routine won’t hurt.
Just don’t forget to stretch afterward; you don’t want to know what dancers' leg cramps feel like.