I have been waiting awhile to address this issue. I will keep this short and start off by stating that if you know the specific and multiple functions of the ACL ligament then you should have no problem constructing a proper program that minimizes undue stress to this tissue and many others. If not then I will disclose what the ACL is, how it naturally operates anatomically, why it is often injured during activity, and how to help counter this with your training.
The ACL serves two primary functions at the knee joint. It's simplest function is to resist either the tibia (lower leg) or the femur (thigh) from extending or rotating too far forward or too far back, depending on whether or not the foot is in contact with the ground (closed chain) or off the ground (open chain). In other words, the ACL helps to keep the knee from hyperextending. The other function of the ACL is to act as a rotary constraint at the knee joint. To illustrate this, take your knee and wobble or move it from side to side and around and around. The ACL is one of the key structures preventing your two legs from separating and falling off of one another. Practical training experience will reveal that poor performance and control from muscles surrounding the knee joint, is one of the leading causes of non-contact ACL injuries, and it is very unfortunate because I think it is a relatively easy fix.
Before I continue I should mention that there are exceptions in everything and ACL injury issues are no different. Upon research you can conclude that the female population is notorious for suffering more ACL injuries than their male counterparts and there is a number of proposed reasons as too why this is true. First, during menstrual cycles females secrete more estrogen and the release of this hormone causes laxity or looseness in the ACL causing the knee to become more unstable which can predispose them to injury. Secondly, females have a more pronounced intercondylar notch within the knee joint, and it can severe or impinge the ACL as it travels through the knee and over time the tissue could potentially tear or rupture. Thirdly, women do not grow as much muscle and other connective tissue and the lack of density here can pose problems and make injury more likely compared to their male counterparts. And last but not least, most women rarely strength train, therefore they are not as strong or as resilient as males who typically do strength train. The media has reinforced the misconception that women who lift weights are going to bulk up or become injured. This is simply not true. Unless women have a RARE predisposition to building muscle, lifting weights will not cause women to bullk up. This is because they naturally possess lower androgen/growth hormone levels relative to males. Authorities have noted that women secrete 80-100 times less Testosterone than men. Moreover women typically do not eat nearly enough calories to support high quantities of muscle growth.
Other causes for ACL injuries for both men and women include, poor hamstring/quad strength ratios, fatigue-overtraining, weak glutes/external hip rotators, poor footwear, and poor coordination levels.
Next, I will outline some training ideas to help keep the ACL healthy over the long-term.
“Pre-habbing” or strengthening the ACL and preventing injury to the ligament is really not that complicated. All you need is a structurally balanced training system. Below is a list of basic training parameters to accomplish this objective:
1. Make sure to keep Hip Dominant and Knee Dominant training proportional
2. Always perform a single max effort lower body exercise 1x per week at the beginning of the week. This means a heavy deadlift or squat variation performed for 1-5 reps.
3. Make sure to perform acceleration and top speed training 2x per week to help build strong hamstrings at both the knee and hip joint to help support the ACL. Here are training splits that I utilize for this type of training:
Weekly Training Program:
Mon, Tue, or Wed:
Acceleration Based Training (5, 10, or 20 yard acceleration sprints).
Thurs, Fri, or Sat:
Top Speed Based Training (40, or 60 yard sprints).
4. Implement both “bent knee” and “straight knee” hamstring development drills into your program. Perform one of each for each training day. Below is a list of exercises for each training category:
Barbell hip thrusts
Slideboard leg curl
Single Leg RDL's
Sled Sprints or pulls
5. Perform stretches for the Rectus Femoris, Psoas, Adductors, and the rest of the hip flexors on non-training days 2-3x per week. 3-5 30-60 seconds holds is optimal.
6. Perform a well-rounded plyometric series prior to speed and strength training at the conclusion of your movement prep. Bilateral and Unilateral progressions are essential. Below is a short list of options for each training category:
Box Jumps (Multi-directional)
Tuck Jumps Broad Jumps
Box Jumps (Multi-directional)
Split Squat Jumps
Things To Consider:Perform each variation in a non-continuous fashion and master a “stick” landing pattern. This ensures proper body control, knee stability, and coordination. It also serves as the necessary progression before the athlete is ready for more reactive plyometric variations. The number of ACL injuries is very alarming. Non-contact ACL injuries, and some contact injuries are preventable. It is my hope that with proper training programs, the number of these injuries will decrease.
Travis Hansen NASM