ACL Prevention Strategies – Jumping

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ACL injuries are becoming ridiculously common amongst athletes from the junior high/high school level on through the professional levels of all sports. My personal thoughts on this issue have a lot to do with the poor training programs most of these kids go through. I won’t go there so much in this article, but want I want to look at is how best to prevent knee injuries from jumping.

The act of jumping and leaving the floor is not so much the problem. It’s the fact that what goes up must come down, and it’s not always pretty when it does. Landing incorrectly, with the knees in valgus, is a major cause of ACL injuries. Knee hyperextension is the other common cause of injury, but is a bit of a different animal. Hyper extension injuries are often the result of an inability to control the knee during deceleration so the body tries to pull out of rapid knee flexion and ends up over correcting into hyper extension. With these non-contact injuries, poor strength is usually at the root of the problem. This article will examine strength training as a way to combat ACL injuries.

Landing efficiently involves all of the following:

  • Landing on balls of the feet sinking down into the heels
  • Knees aligned with the mid to outer foot – vs knees buckling in (valgus position)
  • Hips are back absorbing force – this will enhance performance as well if the landing is followed by another jump or sprint in any direction
  • Slight forward lean of the trunk with the back flat

Basically it’s a good squat position!

Many jump programs emphasize landing with correct technique but don’t address the ability to get into a safe landing position. If an athlete lacks the mobility or strength to get into a safe landing position with just his or her body weight, how are they ever going to do it when the forces are higher? When fighting an opponent for a rebound? What if they happen to land on one leg? You get the point.

Looking at the bio-mechanics of landing, the following are all required:

  • Ankle mobility – specifically dorsiflexion
  • Hip mobility and stability
  • Trunk stability
  • Thoracic spine and shoulder mobility and stability – especially for athletes that must go overhead (rebounding, blocking, spiking, serving, etc)

Here is where things get tricky. Most coaches and trainers have no idea how to accomplish any of the above if one or more is lacking in their athlete(s). Unfortunately, many therapists and athletic trainers out there aren’t quite sure either. Sure we can mobilize their ankles, work the core and hips, but how do we put it all together in a way that it comes out functional. All of the above could be wonderful on the plinth, but what about when the athlete tries to squat? Many just fall apart ½ to ¾ of the way down. You wouldn’t believe how times I’ve heard this one, “my therapist/trainer told me squatting to parallel was bad for my knees”. Of course it is when done incorrectly. It’s great for them when they learn to do it the right way, and that is what will protect the ACL in competition and training.

I’m not saying that working on ankle and hip mobility, core stability, etc in an isolated fashion is a bad thing. These things have their place and I have my favorite techniques too, but they need to be incorporated into the actual activity of squatting. My next article will deal with post-ACL rehab and will discuss more of the pre-squat strategies.

The ‘Squat Progression’ is a technique used as a corrective exercise as part of the Functional Movement Screen, and was first presented in Gray Cook’s “Athletic Body in Balance”. This exercise addresses every one of the bio-mechanical factors listed above all in one series of movements.

The athlete begins by going into a hamstring stretch and presses into the medicine ball to engage the abdominals. It is OK to bend the knees to get the palms to the ball if needed. Hold the stretch 10 seconds, and then drop the hips into a deep squat position. The athlete must continue to try to crush the ball but this will get much harder as he/she drops. From the bottom position, the athlete then removes one hand from the ball, turns the head and reaches with the arm for another 10 seconds. Follow this by reaching with the opposite arm. The movement is finished as the athlete takes both arms overhead and stands back up. The athlete will repeat this progression three times, and then perform three deep squats with arms overhead (feet still on the lift). Gradually progress the athlete to a smaller lift and then to the floor.

The ‘Squat Stretch’ is another exercise I’ll use when I don’t have any equipment available, especially when out on the field or in the gym prior to training sessions. The most basic form of the stretch involves starting with feet a little more than shoulder width and facing straight ahead. The athlete goes into a hamstring stretch for 10 seconds placing the hands under the inside ball of the foot. Knees are allowed to bend to get into this position if hamstring length is an issue. The athlete then drops the hips into a deep squat position keeping the elbows between the knees. The goal is to drop below thighs parallel to the floor with knees apart, feet still pointing straight ahead, and head and chest up. Hold the stretch 10 seconds.

Common difficulties with either of these exercises include one or both feet turning out, losing balance backward, and inability to get the head and chest up. The athlete may not be able to reach full depth right away with great technique but work to it.

Drop squats are an advanced progression of these exercises, and train the athlete to get into position quickly and work the ability to decelerate. Starting from a standing position, the athlete drops into the deep squat position maintaining the technique described previously. Arms forward is the easiest position to start with. Taking the arms overhead increases the challenge. Arms can be taken to one side or the other to add a rotary force, and further difficulty can be added by reaching with a medicine ball.

A full deep squat is rarely ever going to be needed in sports, but to be able to achieve this position with just body weight is important. The ability to deep squat gives a ‘buffer zone’ when the forces becomes higher as in landing from spiking a volleyball, making a tackle, or fighting for a rebound.

Now what happens when the athlete must land on one leg?

Landing on one leg still requires a great deal of ankle and hip mobility as does landing on both feet, but the stability requirements are much greater. The muscles of the hip must work harder to absorb force during landing and to prevent the femur from going into an adducted and internally rotated position creating knee valgus. Trunk stability is also critical to ensuring good lower body alignment and maximum protection of the knee.

Training for the single leg landing must first begin with strengthening this pattern. The single leg squat is the best exercise available to address lower body and trunk strength and stability with carry over to athletics and specifically single leg landings. When done correctly, there is no better exercise to activate the glute medius and maximus to control hip internal rotation and adduction. Learning to keep the lower extremity stable with a slow, controlled movement like the single leg squat will go a long way toward preventing ACL injuries.

The most basic form of the single leg squat involves the athlete sitting the hips back like he/she were going to sit down in a chair then standing back up. The trunk should be inclined forward and arms reaching forward to help counter balance the move. The non weight bearing leg should be reaching forward. There are several ways to progress with this exercise, specifically to increase depth of the squat and maximize hip and trunk stability.

  1. Start with a target, such as a bench or chair. Sit all the way back and down to the surface in a controlled fashion. Lean forward and stand back up, still on one leg.
  2. Continue to use a target but now just lightly touch the surface rather than sitting all the way down.
  3. Progressively lower the height of the target until thigh is parallel to the floor. Some of my athletes will break parallel but must maintain knee control (this I will get to in a minute).
  4. Add weight by holding small dumbbells or a medicine ball in the outstretched hands. A weighted vest could also be worn to increase load.
  5. Change hand positions. Take the arms right or left, even overhead but always work to maintain good knee alignment.

In the video, I demonstrate another advanced progression of the exercise using a reactive neuromuscular training (NRT) technique known as ‘forced pronation’. A small wedge is placed under the outer foot to create pronation and greater internal rotation/adduction of the femur. The athlete must fight this position as he or she squats down increasing activation of the ankle and hip musculature to correct. I really only use this with higher level athletes prior to returning to their sport.

Now it’s time to take it a step further and incorporate plyometric drills into the ACL prevention program.

Plyometric training involves quicker, more explosive movements, such as jumping drills, to develop speed and power. These exercises can range from low intensity to high intensity depending on a number of factors. In this situation the lower intensity work is ideal to start and gradually increase the number of jumps, distance, etc as technique improves. Jumping and landing with both feet will come first, but here I will focus on the single leg drills.

Technique, as always, is critical with these exercises. Here are a few of the things the athlete needs to think about during the drills:

  • land on the ball of the foot then sink into the heel
  • land quietly – this means the muscles are doing the work, a hard landing indicates the joints are taking the load
  • land in the single leg squat position – hips are back, knee is in line with the outer foot, the deeper the better.

Some clarification is also needed when it comes to naming the exercises. The term ‘jump’ in plyometric training terms means to go off two feet and land on two feet. ‘Bounding’ drills involve leaping off one leg and landing on the other. ‘Hopping’ involves leaping and landing on the same leg.

I want to stress that the athlete should be able to do 10 good single leg squats on each leg prior to beginning the plyometric portion of the training. Many athletes, especially females, land high and hard increasing the risk of injury. I mentioned early about having a ‘buffer’ zone. The athlete will not normally have to land in a deep single leg squat position, but the ability to do so in a controlled situation means they will adjust better to less than ideal landings in game and practice situations.

Lateral Bounding – stick the landing: the athlete stands on the right leg, leaps to the left landing on the left leg. Land on the ball of the foot and sink into a low single leg squat position. Balance 2-3 seconds and correct knee position if needed prior to bounding back to the right. Start with a total of 10 reps emphasizing technique. Gradually increase the height and distance as long as technique remains strong. This same type of drill can be done bounding forward, forward and diagonal (45 deg), and backward and diagonal (45 deg).

Lateral Bounding – 1-2-3 stick: same idea as above, but now the athlete bounds three times before sticking the landing in the single leg squat position. This can also be done bounding forward, forward and diagonal (45 deg), and backward and diagonal (45 deg). Five total repetitions.

Single Leg Hopping – stick the landing: the athlete stands on the right leg, leaps and lands on the right leg again trying to get into a ½ to ¾ single leg squat position. This can be done forward (easiest), lateral, and backward (most difficult). When hopping lateral, be sure to go both directions. Standing on the right leg and hopping left will be more difficult than hopping right. Stick the landing 2-3 seconds again and work to control knee position. 6-8 reps.

Single Leg Hopping – 1-2-3 stick: same hops as above but now the athlete must hop three consecutive times before sticking the landing. 3 reps max each leg in each direction.

To make things more challenging I will often use 6″ and 12″ hurdles as obstacles to force the athlete to get more height or distance. Always start with the 6″ hurdles and only progress to 12″ if technique remains perfect. If the athlete struggles to clear the hurdle, he or she will not land correctly.

Reaching with the arms is another way to challenge the athlete’s control upon landing. Holding a basketball or small medicine ball overhead or to one side during these drills will challenge the trunk and lower extremity.

Sports are unpredictable at best so train for every possible scenario. Work on mobility and hip strength to achieve a deep squat, increase single leg strength and learn to control the knee, and finally add more force with plyometric drills to prepare your athletes for a return to sports.

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Joe Heiler PT, CSCS

Joe Heiler MSPT is the owner and content manager of SportsRehabExpert.com, a website dedicated to advancing the education of rehab and performance professionals. The site focuses on orthopedic and sports physical therapy topics through webinars, audio interviews, articles, manual therapy and exercise videos, and more.

Joe is also the owner of Elite Physical Therapy and Sports Performance in Traverse City, MI specializing in orthopedics and sports medicine, as well as athletic performance training. He is Graston Technique (GT) Certified as well as a GT Instructor, SFMA and FMS trained, and is passionate about a number of soft tissue and manual techniques including Trigger Point Dry Needling and manipulation.

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