ACL 101

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At STACK, we take pride in being your one-stop shop for state-of-the-art information on athletic performance enhancement and leading industry trends. That's why we took the time to research one of the most frustrating injuries any athlete can suffer—the dreaded ACL tear.

Injuries are part of sports, but you can take responsibility for trying to prevent them, and then be accountable if you do sustain one. Easier said than done, right? To help you out, we called on a few of our top experts to shed light on the different stages of an ACL injury.

ACL Function; Occurrence of Injuries
The anterior cruciate ligament (ACL), located in the interior of the knee, connects the thigh bone to the shin bone and provides front-to-back stability for the knee. Tears most commonly occur during high impact sports that involve a lot of jumping, pivoting and abrupt changes of direction.

Preventing ACL Injuries
Brad Leshinske, founder and owner, Athletic Edge Sports Performance [Evergreen Park, Ill.]
Leshinske: "We've got to look at what leg muscles are being activated and which ones are not, because these muscles are directly responsible for protecting the ACL and preventing tears. The dominant muscle tends to be the quad and front of the leg, and the lesser used muscles would be the hamstrings, hips and glutes. Working single-leg movements helps strengthen these [less developed] areas and also allows me to see if an athlete is deficient on one side or the other. Also, sports are played on one leg to another, so that's the way you should train."

Perform a dynamic warm-up before performing any of these exercises
Single-Leg Squat
• Place one foot flat on ground and rest other foot on bench behind body
• Keeping front knee behind toes, descend into lunge position until front thigh is parallel to floor and back knee is nearly touching ground
• Rise into starting position; repeat for specified reps
• Perform on opposite leg

Sets/Reps/Rest: 3x8 each leg with 60 seconds rest
Coaching Points: Begin with bodyweight; gradually increase to light dumbbells, then eventually use a bar with weight // Keep front knee behind toes while descending // Don't allow chest to fall forward // Don't push with back leg // Keep lead heel flat on ground throughout the movement

Single-Leg Box Jump With Double-Leg Landing
• Assume single-leg stance an arm's length away from six-inch plyo box
• Lower into quarter-squat, then explode through hip, knee and ankle and explosively jump
• Land softly on both legs with knees bent on top of plyo box
• Step down slowly; repeat for specified reps
• Perform set on opposite leg

Sets/Reps/Rest: 3x5 each leg with 60-90 seconds rest
Adaptation: Once you feel comfortable, progress to a 12-inch plyo box
Coaching Points: Use arms to help maximize height during jump // Keep weight over hips when landing // Maintain good posture with back straight and head up

Single-Leg Lateral Jumps
• Assume single-leg stance on left leg and on left side of six-inch hurdle
• Explode through hip, knee and ankle and explosively hop over hurdle
• Land softly on right leg
• Explosively hop back over hurdle and land softly on left leg
• Repeat for specified reps

Sets/Reps/Rest: 3x10 with 60-90 seconds rest

Adaptation: Perform landing on the same leg you hopped with; make sure to perform a set on the opposite leg.

Coaching Points: Use arms to help maximize height during jump // Keep weight over hips when landing // Stick landing before hopping back over hurdle // Maintain good posture with back straight and head up

Benefits: "Performing these exercises will help develop muscle proportion with your glutes, quads and hamstrings while also helping with ankle, hip and knee alignment. It's important to stabilize those joints and strengthen those muscles to help prevent ACL tears."

Jason McVeigh, University of Tennessee head athletic trainer

STACK: How long does it take to recover from ACL surgery?
Jason McVeigh: [Recovering from] an ACL injury commonly takes six months. [If] you tear an ACL and have it repaired, it's going to be around six months before you return to full sports. It can sometimes be four to five months, but it can also be nine to 12 months in some instances, if you have another injury associated with it.

STACK: What do you focus on when rehabbing an ACL after surgery?
JM: Two different things. One is your balance work and the system of your brain feeling the movements in your knee joint and being able to stabilize [and] fire the right muscles at the right time. The second thing is strength of the muscles in the leg, the quadriceps and the hamstrings. Those two muscles need to work together, and there needs to be a good balance between them.

STACK: What happens if the muscles aren't balanced?
JM: If one is overly strong and the other is weak, you can get an imbalance that can cause the dynamics of your knee to be wrong. The rule of thumb is you want your hamstrings to be about two-thirds as strong as your quadriceps.

For more information from McVeigh on ACL tears and other common sports injuries, check out his expert page.

The Mental Side
Philip Rivers, San Diego Chargers QB

San Diego Chargers Pro Bowl QB Philip Rivers tore his ACL during the 2007 AFC Championship game. Below he explains what he learned about the recovery process.

STACK: What did you learn during your rehab?
Philip Rivers: The thing I may not have understood about an ACL reconstruction is your quad, your hip, your calf and your ankle [are all] really key [to getting back on the field]. I'm not really strengthening that graft they put in there. You've got to kind of let that take its course and heal and get locked in there, and get your quad [strength] back and your hip and calf [strength] back.

STACK: How did you handle that?
PR: It's been really weird. It's almost like re-teaching your quad how to fire and work. I think that's been the part I may not have understood, and it's been the hardest part to really fight through. Patience is the word. Everything I understand about this surgery and injury is [that] it has become such a common thing now that the surgery—you've got to have it done right, but it's not the thing that's really the concern. It's what you are doing now.

STACK: How have you handled not being able to do everything you want athletically?
PR: I think the hardest thing is just having the patience and understanding that it's going to come. I feel like I can bend it all the way, I can straighten it all the way, I can walk on the treadmill, I can do the Leg Press, [but] why can't I go [play football]? You've got to understand that it takes time, and I think for me that's [been] the hardest thing. I like to play golf, run around and shoot a little basketball during the [off-season]. Those are the things I haven't been able to do, so I really just had to stick to the plan and understand [the rehab] process.

STACK: What advice can you offer an athlete who just tore his ACL?
PR: The guys who really rehab it and get after it and work it and are smart and don't overdue it, but yet push themselves, they're back and ready to go. The guys that just kind of go through the motions, [in] six months, seven months, their knee is still bothering them into the next season. Be patient, but be diligent in the rehab [process], and you'll be right back on the field in no time.

Visit Rivers' athlete page to watch videos of one of his grueling rehab sessions. 

For more information on the ACL please see the STACK ACL Guide.

Photo Credit: Getty Images // Thinkstock