Part 1 of this series described how to alter biomechanical inefficiencies to better prepare the neuromuscular system, in efforts to decrease the likelihood of suffering a non-contact ACL injury. Part 2 will focus on developing strength with particular attention given to functional movements that integrate the entire body.
Athletic movements require a coordination of power production and stabilization from many muscles to produce a specific outcome. Therefore, when choosing strength training exercises one should minimize the use of isolated movements (e.g. leg extensions) and instead focus on multi-joint, proprioceptively challenging exercises that coordinate movements using the entire body.
The exercises listed below are advanced and should be performed only under the instruction of a certified sports performance professional and when basic foundational exercises, such as squats and lunges in place, have been mastered.
Single Leg Squats
The athlete begins by standing on one leg (Figure 1a). Instruct the athlete to maintain an upright body posture while squatting (avoid swaying the body to either side). When initiating the squat, the opposite leg should be raised to the front along with the arms for the purpose of counterbalance (Figure 1b). The depth reached will depend on the strength of the individual, with the goal being to reach a bottom position with the thigh parallel to the ground.
|Fig. 1a - Beginning position for Single Leg Squat
||Fig. 1b - End position for Single Leg Squat
- Purpose: This exercise requires strength and stability of the lower and upper leg as well as the hip and trunk muscles.
- Variations: Have the athlete perform the exercise either without shoes, eyes closed, or on an unstable surface (e.g., wobble board, foam roller) for increased proprioceptive demand.
- Sets and Reps: Most individuals will find this exercise challenging, therefore beginning with a small number of sets and reps (2-3 sets of 5 reps per leg) is suggested. Once an athlete can execute a full range of motion without a loss of balance with a larger volume (i.e., 3-4 sets of 12-15 reps per leg) one might consider performing the eccentric action (downward phase) more quickly in an effort to accentuate the deceleration ability of the hips and knees.
Walking Lunge with Rotation
An unobstructed area of 15-20 yards is necessary for this exercise. Begin by standing upright holding a ball with both hands perpendicular to your body (Figure 2a). Next, perform linear walking lunges while simultaneously rotating the upper body towards the lead leg (Figure 2b). Perform the exercise for the prescribed distance alternating legs as you travel.
|Fig. 2a - Beginning position for Walking Lunge with Rotation
||Fig. 2b - End position for Walking Lunge with Rotation
- Purpose: Activation of the trunk muscles may be important in the stabilization of the upper leg while accelerating, decelerating, or landing from a jump. Therefore, this exercise focuses on the coordinative ability to step and rotate without unnecessary movements.
- Variations: Perform this exercise at different speeds and different directions (e.g. laterally or backwards).
- Sets and Reps: This exercise can easily be incorporated into a warm-up by walking up and back to the field or court. For example, a soccer player can begin on the end line, walk forward to mid-field, remain facing the same way and return to the end line by walking backwards. A second set of walking laterally should be sufficient to warm-up the legs.
For this exercise secure tubing (with handles on each end) to a stable structure low to the ground. Hold the handle in both hands close to your chest, face perpendicular to the tubing, and step several feet away so there is significant tension on the tubing (Figure 3a). Next, lift and step with the foot nearest the tubing while simultaneously rotating the body so you are now facing the tubing while in a lunge position (Figure 3b). Complete a full range of motion while minimizing ground contact, pushing off the lead leg forcefully to return to the starting position.
|Fig. 3a - Beginning position for Deceleration Lunge
||Fig. 3b - End position for Deceleration Lunge
- Purpose: You should feel a slight pull from the tubing the moment your foot leaves the ground (if not, back up further). This added acceleration will increase to the eccentric loading, and by minimizing ground contact you will train the muscles reactive ability.
- Variations: From the same starting position, use your rear leg to step and perform a cross-over deceleration lunge. Linear and lateral lunges can also be performed using this technique. Choose tubing with a different thickness to provide various resistances that will either increase or decrease the eccentric loading.
- Sets and Reps: Quality is the key for this exercise. Perform 2-3 sets of 5-8 reps with a focus on minimizing the amount of time the stepping foot is in contact with the ground. To maximize the benefits, this exercise should be performed in a non-fatigued state with plenty of rest between sets.
Leg Curls on Swiss Ball
First, lie on your back with both feet placed on a swiss ball. Place both arms out to the side (forming a T). Next, raise your hips off the ground until your body becomes a straight line (Figure 4a). Once a stable position can be maintained use both legs to curl the ball towards the glutes while maintaining elevated hips (Figure 4b), then return to the starting position.
|Fig. 4a - Beginning position for Swiss Ball Leg Curl
||Fig. 4b - End position for Swiss Ball Leg Curl
|Fig. 4c – One-legged Swiss Ball Leg Curl
- Purpose: The hamstrings are bi-articular, meaning they cross both the hip and knee joints. By elevating the hips then curling the ball, you are performing both actions of the hamstrings simultaneously (hip extension and knee flexion). Plus you have the challenge / benefit of having to use the trunk to stabilize the body while performing the exercise.
- Variations: Perform the single leg version (Figure 4c). Once the hips are elevated raise one leg off the ball and perform the curl with the other leg. You can also vary your arm position by placing the arms along side the body or crossed over your chest to increase the demand on the trunk.
- Sets and Reps: The advantages of this exercise are the same factors that will make it challenging. Remaining stable while the hips are raised may be difficult and therefore limit the number of repetitions that can be performed. Depending on the athlete , the ultimate goal will probably be to complete 2-4 sets of 12-15 reps, but start smaller and progress with good form.
Minimizing the likelihood of sustaining a non-contact ACL injury takes a conscious effort to change mechanical inefficiencies, properly train the neuromuscular system, and enhance the coordinative abilities of the core and legs. By incorporating the strength training exercises in this article and providing instructions on proper motor skills (described in the first article of this series) we can begin to take an active role in ACL injury prevention.
- Garrick, JG and Requa, RK. Anterior cruciate ligament injuries in men and women: How common are they? In: Prevention of Non-contact ACL Injuries. LY Griffin (Ed.) Rosemont, IL: American Academy of Orthopaedic Surgeons, 2001, pp. 1-10.
- Lephart, S. and Riemann, BL. The role of mechanoreceptors in functional joint stability. pp. 45-52.
- Hutson, LJ and Wojtys, EM. The influence of the neuromuscular system on joiont stability. pp. 53-62.
- Kibler, WB. The neuromuscular contribution of the hip and trunk to ACL injury. pp. 63-68.
- Griffin, LY. The Henning Program. pp. 93-96.