A jump-training program that focuses on controlled landings, strengthening the hamstrings, and proprioception shows promise at preventing ACL tears.
By Guillermo Metz
Guillermo Metz is an Associate Editor at Training and Conditioning.
From high school-level participation to the WNBA, women's basketball has never been more popular. We see more women flying to the hoop on our television screens than ever before, and athletic directors are putting more and more money into this potential revenue-producing program. Behind the scenes, however, many athletic trainers fear there is one thing holding the game back: way too many ACL injuries.
As we've written about before in these pages (see Training and Conditioning October 1996), research shows that the incidence of significant knee injuries among females is roughly five times higher per player hour than that for males. And the sport of basketball has been hit hardest. From Nikki McCray to Kellie Jolly, women hoopsters too often count scars along with baskets and rebounds.
As research continues on why--theories include basic anatomical differences between the genders, hormonal influences, and/or neuromuscular deficiencies among females--Tim Hewett, PhD, the Director of Applied Research at the Cincinnati Sportsmedicine Research and Education Foundation, and his colleagues have been focusing on how--how to prevent knee injuries in female athletes. And they seem to have found some solutions.
Over the past six years, Hewett and his group have developed a training program that has been tested on high school female basketball, volleyball, and soccer players, which significantly decreased their incidence of ACL ruptures. The program also improved athletes' vertical jumping ability. The results, which were presented at last year's annual meeting of the American Orthopedic Society for Sports Medicine, are in press in the American Journal of Sports Medicine.
In the study, Hewett and his colleagues recruited 43 sports teams (girls' and boys' soccer and basketball, and girls' volleyball)--a total of 1,263 student-athletes--consisting of 366 girls who would go through the program and 463 girls who would not, along with 434 boys who would also not be trained and would serve as the control population. Ninety-four percent of the athletes were followed for at least four weeks--the minimum required for inclusion in the study. Athletic trainers at each school then tracked serious knee injury rates, defined as a knee ligament sprain or rupture that forced the athlete to lose at least five consecutive days of practice and competition. All ACL ruptures were confirmed by arthroscopy and MCL sprains were diagnosed based on pain along the MCL and increased rotation with a valgus stress test. No re-injuries were included in the study.
At the end of six weeks, there were 14 serious knee injuries: 10 of them among the untrained girls, two among the trained girls, and two among the untrained boys. Both injuries sustained among the trained girls resulted from direct physical contact with another player; eight of the 10 among the untrained girls were non-contact.
Hewett's program is neither revolutionary nor radical. It basically trains athletes in jump technique and selectively targets weak muscle groups, and adds to what many of the top basketball programs are already doing (see sidebar, "Tennessee's Training Tips"). The difference, however, is that this is the first time a training program has been able to succinctly document a decrease in ACL and MCL injury rates.
HAM-TO-QUAD RATIOS
Hewett began looking closely at the biomechanics and neuromuscular patterning of high school girls' knees when he started at the Foundation in 1993. Because many ACL injuries occur when the knee is hyperextended, he expected to find that females land from a jump with their legs more fully extended than males. However, he found that knee extension at landing was basically the same between the genders. Instead, his research team found that the abduction/adduction moments at the knee were what varied most between males and females.
"What you'll see if you watch young female athletes jump is that they tend to be ligament dominant," Hewett says. "They'll land mostly valgus or mostly varus, depending on their technique, and let the knee go out or in until the ligament picks up the slack, rather than controlling it with their knee musculature."
Hewett's first study tested high school male and female volleyball players in a biomechanical/neuromuscular gait laboratory. "The main thing that we found," he says, "is that females have, on average, a hamstrings-to-quadriceps peak torque ratio of less than 50 percent at high speeds (300 degrees per second). If you look at some of the physical therapy/rehabilitation journals and books on isokinetic training, they would tell you that that's pathologic; they cite that most people have a ham-to-quad peak torque ratio of 70 percent. If you look at the males, they have ham-to-quad ratios of near 70 percent, but that's certainly not where these females were. That really surprised us.
"We also had the athletes do a volleyball block on a force plate," he continues, "and we were surprised to find that right at the point when they hit that plate, males are activating their gastroc and their hamstrings at three times the level that females are. In other words, at the point of landing from the volleyball block, females are activating their extensors--their quads--relatively much more. We also found that the women were imbalanced side-to-side--their hamstring strength on the non-dominant side lagged the dominant side by as much as 15 to 20 percent."
These were not novice athletes. In addition to some of the country's best high school volleyball players, Hewett and his colleagues tested elite college athletes. "Some of the very best female athletes we looked at had some of the worst ham-to-quad ratios we'd ever seen," he says. "They tend to have overdeveloped quads. We've had Division I All-American volleyball players in the laboratory who have had hamstring-to-quad ratios around 40 percent. They're great athletes, but my guess is that they're at high risk for knee injury.
"The hamstrings are an ACL agonist--they resist forces that strain the ACL," Hewett explains, "whereas quadriceps contraction at low knee flexion angles acts as an ACL antagonist, significantly increasing strain on the ACL."
TRAINING THE DEFICITS
Having found one possible mechanism of injury--or at least a weak link--Hewett set out to design a training protocol that would address this basic neuromuscular deficiency. This was the first phase of the study, and was published in 1996 in the American Journal of Sports Medicine.
"We put a program together that would train the girls better technique for take-off and landing and teach them to stabilize the knee joint and control it in space better," Hewett says. "And one of the bonuses of the program is that you're also going to gain jump height."
Hewett and his colleagues examined several existing programs, including the 1984 Olympic men's volleyball team's training program, the University of Alabama at Birmingham's women's basketball training program, a program that UCLA had published, and several high school programs. They added their own extensive experience in plyometric training and developed a program that combined stretching, plyometrics, and weight training, with an emphasis on activating the hamstrings, especially through high knee flexion angle jumps.
"The techniques we used," Hewett says, "stressed good posture--the body aligned with the chest over the knees and the knees over the balls of the feet. We taught the athletes to jump straight up with no forward or backward or side-to-side motion. We taught soft landings, toe-to-heel rocker landings, and getting them to instantly recoil and get ready for the next jump. And we taught them to listen to their landings. With young, moderate-level female athletes in particular, you can hear their feet smack the floor on landings, and you can teach them to get rid of that.
"The other thing we threw into our program that a lot of the other ones didn't have," he adds, "was using a lot of verbal and visualization cues to prompt proper form: 'I'm jumping up and I'm straight as an arrow. I'm landing, I'm light as a feather as I land. I'm a shock absorber and I recoil like a spring for the next jump.'"
The entire training program, which he calls Sportsmetrics, is broken down into three phases over a total six-week period. Sessions are held three times a week, on alternating days, with each session consisting of about 20 minutes of stretching, 25 minutes of plyometrics, and 30 to 35 minutes of one-circuit weight training, concentrating on closed-chain leg presses.
"Phase I is about technique," Hewett says. "We spend the first two weeks just on technique. In Phase II we increase the volume--now that they've got good landing technique, we're trying to increase their strength. In Phase III, the performance phase, we bring the volume back down and look for more quality and greater jump height with each jump."
Each session begins with standard stretching: calf, quads, hamstring, hip flexor, hip extensor, and some upper-body stretching. In Phase I, athletes do 10 or fewer jumps, beginning with wall jumps. "Some people call them ankle bounces," Hewett explains, "where you're keeping your hands up in the air and, with your knees slightly bent and your hands raised over your head, you bounce up and down on your toes. That's used just as a warm-up, to get them thinking about using their gastrocs and pushing off from the floor. There was no set number of jumps to be performed--we were concentrating on good form. As they got fatigued and their form got poor, we would ask them to stop."
This is followed by tuck jumps. Athletes start in a standing position and then jump, bringing both knees up to the chest as high as possible. Next, athletes perform broad jumps, concentrating on sticking the landings. "That's one of the important parts of this program," Hewett says. "We would make them do one-legged or two-legged broad jumps and try to get them to maximize how far they could go, but it didn't count unless they could stick the jump and hold it for five seconds. We would have them do those in reps--say, five good ones.
"Then we would have them do squat jumps," he continues, "where the athlete stands with both arms overhead, jumps straight up, and lands in a squatting position, touches the floor and then comes up again. We also did cone jumps, where athletes go side-to-side, to teach them abduction/adduction control; then front-to-back, which is really good to teach them control of the knee joint. We would teach them not to double hop but to control the jump--jumping from one side, back to the other, recoiling on that jump and taking off again.
"We would finish the phase with more proprioceptive-type jumps, like 180-degree jumps, where they would jump backwards but turn 180 degrees while jumping so that they would land facing the other direction. We would teach them bounding--pushing themselves forward, landing on the other leg, and then recoiling to jump off again."
In Phase II, the fundamentals phase, the exercises increased in volume and emphasized strength, power, and agility. In this phase, Hewett would throw in a couple of more-difficult jumps, like the scissors jump or a hop-hop-stick, where athletes would have to double hop and then hold the landing.
In Phase III, the performance phase, the volume was decreased and the emphasis was put on making sure that every jump was perfect--and as high as possible. This phase of the training program also introduced more advanced plyometrics. Using mats that were folded over to a height of about eight inches, athletes had to jump off of the mat, controlling the jump and then focusing on and controlling the landings. They then progressed to cone jumps on the same eight-inch mat. These exercises concentrated on the athletes feeling where their knees were and understanding when their stopping point was so that they could take off again cleanly.
Through this training program, Hewett and his team found that they could bring hamstrings-to-quadriceps torque ratios on the non-dominant side up as much as 40 percent and on the dominant side about 20 percent. This brought the girls' overall ham-to-quad ratios, on the mean, to about 65 percent (the boys were at about 67 percent).
"The other thing that we showed," Hewett says, "was that just with all of these simple techniques and increases in strength, we could decrease landing forces down from about four times their body weight to about three times their body weight. So, we're basically taking a person off their back through this training."
INITIAL FEEDBACK
Nearly all of the high schools that were used as testing grounds are still using the training program in one form or another, and over 100 copies of a videotape detailing the program have been sold thus far. So far, coaches and athletic trainers have found the program easy to implement and effective.
"Going into the program, I was pretty skeptical," says Julie Thoman Perry, Head Girls' Volleyball Coach at St. Ursula's Academy, in Cincinnati, who has taken the state title six years running, and used the program with her team for the past three years. "Now, I'm very positive about it. We didn't really have a problem with a lot of injuries occurring, but it's increased the (girls') jumps one to three inches. I think that's crucial--to be the best, you have to keep improving."
Evan Massey, Head Girls' Basketball Coach at Galesburg (Ill.) High School got wind of the program after the study had been completed. Because he had a spate of knee injuries in one year, he was looking for just such a program. "From July 1997 to July 1998, we had four female players who tore their ACLs," he says. "They were all varsity-level players and non-contact injuries.
"That had been my 20th year coaching, and I'd only had one ACL injury prior to that season," he says. "We did a lot of examining of what we were doing and looked at what other people were doing. We were starting to put together a training program with Scott Sunderland, (Head Athletic Trainer) at Knox College, when he heard about Tim Hewett's. Scott really recommended that program.
"What sold me when we got the tape was how simple it is," Massey continues. "With high school athletes, in the off-season you can't ask a lot of time of them. This program is very efficient and doesn't require them to spend hours jumping. With the jump phase, by the time the kids stretched and warmed up, we never spent more than a half hour on those exercises.
"We had other people look at his program and what we had been doing," he says. "We decided to keep our weight training program but add some exercises to work the hamstrings even more. We also implemented as part of our weight routine a lot of balance exercises--minitramps, Styrofoam cylinders, balance boards. And then in the fall we implemented the jump phase of Hewett's program. Once our season started, we maintained our weight program and two days a week we would take five to 10 minutes at the beginning of practice and do some of the jump exercises."
Massey adds that when he and Sunderland initially looked at the tape, the first thing they noticed was how the program could be effective at reducing landing impacts. The actual results backed that up. "We didn't do any tests to be able to definitively say that they land more softly," he says. "But we did have some kids come in and start the program after about five weeks--these were good athletes who I would characterize as being smooth in their motions--and it was amazing to see and hear how much better the kids who had already gone through the training were than they were. I found that really impressive."
According to Sunderland, the training program also helped the student-athletes in another area. "When they had four ACL tears in one year," he says, "the other kids on the team got to the point where they were a little bit scared to go back out on the court. So, they really needed something that was very concrete that seemed to be really well-worked-out scientifically, which this program was. When they implemented it, it gave the kids not only physiological prevention, but also a level of psychological prevention." This year, the team took second in the state, injury-free.
At Knox College, Sunderland has also implemented elements of the program with his girls' soccer and volleyball teams, as well as both girls' and boys' basketball. What he has found to be the most important element of the program, he says, is its focus on technique. "These exercises may be the best at training proprioception and lower-extremity strength, but the thing that's most important about them is not so much the specific exercises themselves, but the way in which they're taught. You want them to be performed perfectly every time, and the most concentration is put on the landing."
ENDING THE EPIDEMIC?
So, is Hewett's program the panacea for the female ACL epidemic? Even Hewett doesn't think so, but it's a great start. "I think we found at least part of the answer to preventing these injuries. We have ongoing studies on estrogen levels--looking at the effects of the different phases of the menstrual cycle on coordination and neuromuscular functioning. We're also measuring Q-angles and that sort of thing. But, one thing that we can say about the training--training can't do much about anatomy, but I think that it may be able to override some of these hormonal and anatomical factors."
Dr. Hewett welcomes inquiries about his research. Persons interested in obtaining a videotape and manual for implementing the Sportsmetrics training program in their schools should contact the Cincinnati Sportsmedicine and Orthopedic Center at (513) 559-2818.
Sidebar
The University of Tennessee Lady Vols are at the top year after year--here's part of what keeps them there.
Jenny Moshak, MS, ATC, CSCS, Assistant Athletic Director for Sports Medicine at the University of Tennessee, and former Head Athletic Trainer for the Lady Vols, has been running the women's basketball team through a training protocol aimed at injury prevention and increasing performance for several years. Her program addresses some of the same concerns as Hewett's program.
"The important elements of our program are threefold," she says. "One, we try to teach our athletes to use their hips instead of their knees for motion--for jumping, absorbing the jump, and change-of-direction. That should not only decrease the incidence of ACL injuries but also increase performance. And, one of the problems we have more trouble with is patello-femoral and other chronic overuse conditions as opposed to acute injuries, which is also addressed by getting them to use their hips more.
"The second thing we do is a lot of proprioception, getting the athletes to know where their bodies are in space and time. We teach the athletes to balance, first with their eyes open, then with their eyes closed, putting their bodies in situations where they have to correct themselves. We do this both in the rehab setting and for prevention. We have a lot of exercises the athletes go through as a team that only take about five minutes."
These exercises include balancing activities on equipment such as BAPS boards, rocker boards, and balance beams, and work with physio-balls in the weight room. The athletes lift weights while sitting and laying on physio-balls and on platforms that have balls on the bottom. The weight loads are light, but the exercises emphasize being able to perform the lifts while balancing.
"The third thing we do," Moshak says, "is we look at their biomechanical chain. A lot of our athletes are pronated--we'll put their foot into neutral with an orthotic and we hope that that eliminates a lot of the stress on their joints as well.
"You try to minimize the risk as much as possible," Moshak says. "Sure, you could have the strongest, most skilled, most flexible athlete, and they could still subject their knee to forces that are going to tear their ACL. But what you want to do is stop the occasions where a kid tears the ACL because she's falling out of control. When you start seeing a decrease in the number of overuse injuries and also an increase in performance, that pleases coaches and athletes."