Plyometrics in ACL Rehabilitation: The Melbourne Protocol

Anterior Cruciate Ligament (ACL) injuries are among the most debilitating injuries in sport, particularly in activities involving rapid changes in direction, jumping, or pivoting. Rehabilitation from an ACL injury is complex and multifaceted, requiring careful planning and execution. Plyometrics (exercises involving explosive movements to increase power and agility) play a critical role in the latter stages of ACL rehabilitation.

In this article, I'll explore the importance of plyometrics in ACL rehabilitation, with specific reference to the Melbourne ACL Protocol and the research conducted by Mick Hughes, a renowned Australian physiotherapist and sports injury specialist. I'll also provide examples of effective plyometric exercises you can incorporate into rehabilitation, whether you're recovering from an ACL injury or not.

Understanding Plyometrics and Their Role in ACL Rehabilitation

The term "plyometrics" originates from the Greek word pleythyein, meaning "to increase or augment." While plyometric techniques were practised in Eastern countries as early as the 1960s, the term itself was first coined in 1975 by American track and field coach Fred Wilt. After studying Dr Verkoshansky's training methods extensively, Wilt combined the Latin roots plio ("more") and metrics ("to measure") to create a term reflecting the purpose of plyometrics: enhancing speed and power.

In essence, plyometric training aims to make movements more explosive. Although it began in track and field, this approach has since proven beneficial across a wide range of sports, helping athletes improve performance regardless of discipline.

Plyometric exercises are designed to improve the muscle's ability to produce and absorb force quickly, which is essential for jumping, sprinting, and changing direction. These exercises involve a stretch-shortening cycle, where the muscle is rapidly stretched (eccentric phase) and then immediately contracted (concentric phase). This type of training enhances neuromuscular coordination, strength, and power, all critical in ACL injury rehabilitation.

One of the key goals in ACL rehabilitation is restoring the knee's strength, stability, and function to pre-injury levels (or even better). Plyometric exercises are particularly effective because they mimic the dynamic, high-impact activities often responsible for ACL injuries in the first place. By progressively introducing these exercises into a rehabilitation programme, patients can regain the explosive strength and neuromuscular control necessary to return to sport safely and effectively.

The Melbourne ACL Protocol: A Structured Approach to ACL Rehabilitation

The Melbourne ACL Protocol is a comprehensive and evidence-based rehabilitation programme that has gained recognition for its effectiveness in guiding patients through the recovery process.

The protocol is divided into several phases, each with specific goals and criteria that must be met before progressing to the next phase. Plyometrics are introduced in the intermediate and advanced phases, once the patient has regained sufficient strength, stability, and range of motion in the injured knee. These exercises challenge the knee in ways that replicate the demands of sport, helping to prepare the patient for a safe return to activity.

Plyometric Exercises for ACL Rehabilitation

Incorporating plyometric exercises into ACL rehabilitation can be highly effective when done correctly. Below are examples of plyometric exercises I often use in the intermediate and advanced stages of ACL rehabilitation.

1. Box Jumps

Box jumps are a fundamental plyometric exercise that helps improve explosive power and knee stability. Start by standing in front of a sturdy box or platform. Bend your knees and hips slightly, then jump onto the box, focusing on a soft landing to minimise impact on the knee. Step down and repeat. This exercise can be progressed by increasing the height of the box or incorporating a lateral movement before the jump.

2. Lateral Bounds

Lateral bounds are excellent for improving lateral stability and mimicking the side-to-side movements often seen in sport. Start by standing on one leg, then push off laterally to jump to the other leg. Land softly and immediately push off in the opposite direction. This exercise challenges the knee's ability to stabilise during dynamic movements, which is crucial for preventing re-injury.

3. Single-Leg Hops

Single-leg hops are an advanced plyometric exercise that builds unilateral strength and balance. Start by standing on one leg, then hop forward, focusing on landing softly and controlling the movement. This exercise can be performed in different directions (forward, backward, and laterally) to challenge the knee from various angles. The knee is responsible for absorbing 65% of the forces when landing, so this is a crucial test.

4. Depth Jumps

Depth jumps involve stepping off a box, landing softly on the ground, and immediately jumping as high as possible. This exercise helps improve the stretch-shortening cycle and increases explosive power. Depth jumps should only be introduced when the patient has demonstrated good control and strength in other plyometric exercises.

5. Tuck Jumps

Tuck jumps are a dynamic exercise involving jumping straight up and bringing the knees towards the chest at the peak of the jump. Focus on landing softly and maintaining proper knee alignment throughout the exercise. Tuck jumps are great for improving vertical jump height and knee stability.

The Psychological Side of Plyometrics

There are many variations of these exercises which can help identify how an athlete generates force, absorbs force, and transitions between these two variables. But I'm also well aware of the psychological impact an injury can have on athletes.

I refer to low-level plyometrics as a "leap of faith." This relates to the competence, confidence, and capability to perform a jumping movement. It's scary for those who haven't performed a jump for six months or more since their injury, operation, and post-operative care.

With a graded strength approach, a systematic rehabilitation process as outlined in the Melbourne ACL Protocol, and supportive, empathic guidance from a skilled therapist, I can guide you every step of the way back to your sport and passion.

In my professional opinion, if you haven't completed a plyometric assessment with a therapist or coach, you haven't completed your ACL rehabilitation.

Final Thoughts on ACL Recovery

If you or someone you know is recovering from an ACL injury, consult with a physiotherapist who is knowledgeable about the Melbourne Protocol and the role of plyometrics in rehabilitation. By integrating these exercises into your rehabilitation programme, you'll be taking a significant step towards a successful recovery and a strong, resilient return to sport.