Plyometrics are described as rapid and powerful movements. These movements first cause a muscle to lengthen, then shorten. The combination of lengthening and shortening the muscle at a fast pace increases the power of a muscle. Plyometrics aid in the prevention of ACL injuries by training the muscles to react at a faster rate preventing the knee from shifting. Examples of plyometrics are single leg cone jumps, squat jumps, single leg bounding, and ladder drills. The goal when performing these drills is to jump immediately again after making contact with the ground. The exercises are generally performed for about 30 seconds, however when first starting the drills, a shorter time may be required to begin and then gradually increased with practice.
Balance and stretching are also key factors to preventing ACL injuries. It is important to thoroughly stretch the calf, quadriceps, and hamstring muscles. Stretching these muscles will ensure that the muscles are not too tight which could cause a muscular imbalance and increase your chance of injury. Balance or proprioception is also a goal in ACL prevention as it can allow muscles to work together to stabilize the body on various surfaces. If the body and knee cannot quickly react to surface changes, an ACL injury could occur. Balancing exercises can be performed on one leg, on uneven surfaces such as a BOSU Ball, and can incorporate throwing a ball while balancing to increase muscular stability and neurologic reaction time.
Strengthening is the final aspect of an ACL prevention program. It is essential to strengthen not only the hip and thigh musculature, but also the core. Strengthening the musculature of the legs allows for a more stable knee joint which decreases the risk of ACL injury. Core and leg strengthening can be done using the body’s weight through exercises such as walking lunges, squats, sit ups, and planks. Exercises such as walking lunges are also an adequate exercise to warm up and loosen the muscles before activity.
While performing ACL prevention programs, it is imperative to focus on technique more than the number of repetitions completed in the allotted time. When jumping during plyometrics, the proper landing technique is to bend at the knees and hips to absorb the force rather than keeping the knees and hips straight causing the force to compress the joints. The phrase ‘light as a feather’ is used to describe how to land, meaning land as softly and quietly as possible to absorb the shock. The toes are to remain pointing forward at all times, and the knees are to stay in line with the toes. This ensures that the muscles are functioning together providing the best stability for the ACL. Poor technique can lead to a muscle imbalance, decreasing the stability of the knee.
ACL prevention programs can be done in 15 minutes and research has found them to be beneficial to help prevent injury. These programs are recommended to be performed at least 2-3 times per week with at least 1-day rest between each session. A minimum of 6 weeks is needed to provide the best results. Although it appears to be a hassle, these programs only take a few minutes to perform and can be done using simply the body’s weight, while providing a decreased risk of a serious ACL knee injury.