Here’s the lowdown on how you can train to prevent your ACL from going down

By Jackie Ansley

ACL. The mere thought sends shivers up and down the spine of every young athlete. The Anterior Cruciate Ligament (ACL) injury has become devastatingly common among today’s young players, especially females. A recent NCAA study showed that the likelihood of a female sustaining an ACL injury is two to eight times greater than males.

Research has shown that one of 10 college female athletes – and one out of 100 high school female athletes – experience an ACL injury. The numbers are staggering. The growing concern is causing more teams to develop prevention programs.

Training programs designed to specifically address the risk factors associated with an ACL injury are being successfully implemented. The programs are a combination of common exercises with modifications in technique and instruction, and novel exercise designed specifically for this purpose. Coaches at all levels can assist in the prevention of ACL injuries by including components of these programs into their team workouts.

The ACL breakdown

There are two types of ACL injuries: those that occur as a result of direct contact with another player or object and those that have no associated contact. These injuries are referred to as non-contact and include situations such as landing from a jump, cutting and stopping.

Estimates show that 70 percent of ACL injuries do not involve contact. While the exact mechanism for them is not known, several potential risk factors for non-contact injury have been identified: environmental (equipment, shoe-surface interactions), anatomic (knee angle, laxity, notch size), hormonal and biomechanical (muscular strength, body movement, skill level, neuromuscular control). Of the identified factors, only the biomechanical risks can be affected by training.

One of the biomechanical factors is a muscle strength imbalance between the hamstrings and the quadriceps muscles of the thigh. When the quadriceps contracts, it pulls the lower leg forward, putting stress on the ACL. The stress increases as the knee becomes more extended, thereby increasing the risk of injury. Hamstring contraction counteracts the force of the quadriceps on the ACL by pulling the lower leg rearward, protecting the ACL from stress.

Female athletes tend to have imbalances between the strength of the quadriceps and hamstrings – with the quadriceps dominating in strength. Hence, when the quadriceps contracts forcefully, as during a sudden stop or cut, the hamstring is unable to counter the force to protect the ligament. Additionally, females demonstrate less gluteal activation when cutting, which can result in decreased hip control and improper knee position during movement. Designing a strength-training program that emphasizes the hamstrings to balance out the knee stabilizer strength is believed to be an essential component to preventing ACL injury.

Another factor is the technique used when landing, planting and cutting. Females tend to perform these activities in a more upright position resulting in greater hip and knee extension. When the knee is more extended, the ACL is under increased tension, making it more susceptible to injury during forceful quadriceps contractions.

In addition, analysis of video has shown that females tend to perform planting, cutting and landing movements by turning the knees inward. This position can exaggerate anatomical risk factors such as Q angle stress (the angle formed where the femur meets the tibia). Increased Q angles can lead to more rotational forces on the ACL when the knee rotates during movement and a greater chance for injury.