Experienced weight trainers know that the benefits of strength development carry far beyond simply lifting more weight, from improving sports performance to enhancing the dynamic stability of joints, which can help reduce the risk of injury.
Recognizing this, colleges around the world employ strength and conditioning coaches to work with their athletic teams. Yet one area of strength training has fallen short with female athletes, in which tears of the ACL -- or anterior cruciate ligament -- have actually increased dramatically over the years. Such injuries are now, in fact, common in female volleyball, softball, basketball and soccer players. The culprit may lie in failing to establish proper neuromuscular control (motor skills) during strength training.
Sean Flanagan, Ph.D., ATC, CSCS, associate professor at California State University Northridge and author of the textbook Biomechanics: A Case-Based Approach, had the following to add to this problem/solution:
Any time you slow down or lower your body towards the ground, the body has to absorb energy. Ideally, most of that energy should be absorbed by the muscles of the lower extremity. Improper technique or weakness can decrease the amount of energy absorbed by the muscles. Energy not absorbed by the muscles will be absorbed by other structures, such as the ACL. Excessive energy absorbed by structures ill-equipped to handle that energy will lead to injury.
One improper technique implicated in ACL tears is the motion of bowing inward at the knees during a squat or lunge position. We have all seen beginners learning to squat, with some of them allowing their knees to collapse towards each other instead of remaining straight in line during the squat. The caving in, or inward collapse of the knees, is technically known as a valgus stress, or load, on the knees.
One reason this occurs is because some of the gluteal muscles are not working well enough. The outer gluteal muscle is the gluteus medius. It abducts, or moves the thigh outwards. This action helps prevent the thigh from moving inward, thus allowing the knees to stay in line and not collapse inward. Poor control or weakness of the gluteals will lead to the valgus collapse, and thus increase the energy absorbed by the ACL.
Another cause of ACL injury is when the leg is stiff, or straight, when landing from a jump or changing position quickly. The inability to bend the knees and hips to a deeper position can be due to weakness of the gluteus maximus, hamstrings and quadriceps ("quads"). They simply don't have enough strength to bend the knees and hips to so that the muscles absorb energy. As a result, the knee can't bend enough because the muscles are too weak. The control of the muscles is insufficient. Energy not absorbed by the muscles is then transferred to passive structures such as the ACL.
The best way to help an athlete reduce the risk of this type of injury is to add a couple of exercises to the strength program and pay very close attention to the form or technique. The traditional squat should be used to develop strength in the gluteus maximus, hamstring and quadriceps. This technique should not allow the inward collapse or caving in of the knees towards each other, so keep the knees in line with each squat. It is better to squat with lighter weight in perfect form rather than heavier weight with bad form. You may add weight as long as the technique remains correct.
A single-leg exercise, such as the traditional lunge or the walking lunge, is a great learning tool and helps strengthen as well. Again, as the athlete lunges, the knee must stay in line with the foot and hip and not collapse inward in a valgus stress. This is critical. The depth of the lunge can be shallow initially and become deeper as the athlete becomes stronger. Once this exercise is easy, it can be made even better by having the athlete hold dumbbells while lunge walking. Other single-leg exercises, such as split squats, step-ups and single-leg squats, can also be incorporated.
Raising one leg to the side (abduction) while standing with a cable and cuff attached to the ankle is helpful. The muscles that pull the leg to the side (gluteus medius) are working on the weight bearing leg also as you raise the other leg with the cable and cuff attached.
These few exercises can go a long way to help reduce ACL tear injuries in not only young female athletes, but others as well.