ACL Plyometric Exercises

The purpose of this blog is to discuss 4 stages of plyometric training that can serve as a guideline following ACL reconstruction. I will discuss what plyometric exercises to perform, when it is safe to begin them, and how you can implement and progress them over time. 

The exercises and stages are based on a 2021 article by Buckthorpe and Della Villa.

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Plyometric Exercises Overview

The goal of these plyometric exercises are to maximize performance, improve movement quality, and reduce risk of reinjury following an ACL reconstruction.

As outlined by the authors, progressing through these 4 stages will be primarily based on 3 themes:

Theme #1 –  The intensity, complexity and loading demands of the task.

For example, you will see a general theme of:

• Progressions from linear to multiplanar movement.
• Gradual reductions in ground contact time.
• Increases in speed, effort and volume.
• A progression from bilateral to unilateral plyometrics.

Stages will generally consist of 4 types of plyometric exercises.

• Bilateral off-set. This involves landing on one leg before taking off on the other. An example is an alternating box split jump.
• Bilateral asymmetrical. Both feet take off and or contact the ground simultaneously but in different positions, such as with a split squat jump.
• Bilateral symmetrical. Both legs accept and produce force simultaneously, such as with a bilateral squat jump.
• And unilateral. Eccentrically accepts load on one leg and concentrically develops force and power on one leg. This can be on the same leg such as with a single leg box jump or from one to the other such as with alternating lateral jumps.

Theme #2 – Your capacity to tolerate these demands.

There will be prerequisite criteria to ensure you possess the appropriate range of motion, strength and movement quality prior to starting exercises in a given stage.

While the focus will be on function, time is still a consideration. Plyometric exercises will likely start around the 3 month mark or later, with each stage lasting 1-2 months, however “the protocol should always be customized based on the patient’s response.”

Theme #3 – Your response to the task

Exercises should not lead to increases in pain and or swelling, and you want to avoid excessive muscle soreness. This will increase recovery time, making training on subsequent days more challenging.

Stage 1

Exercises will be low intensity, have longer ground reaction times, and consist of bilateral offset, asymmetrical, and sub max symmetrical plyometrics.

Criteria to start stage 1 includes:

• ≤1/10 pain at rest and <2/10 pain during activities of daily living.
• Full knee extension range of motion and knee flexion >120°.
• Less than 20% asymmetry in loading during a bilateral squat.
• Isometric knee extensor strength >70% of the uninjured side.

Here are some examples of Stage 1 plyometrics:

Bilateral Squat Jump

Sub Maximal Squat Jumps to a Box. The box will allow you to focus on concentric power development while reducing landing impact forces. 

During landing, you should aim to demonstrate good knee and hip flexion angles, about 90° each, minimize excessive movement of the trunk and pelvis, and maintain good knee alignment.

Step and Land/Cut

Lunge Push Back. Start feet together and step forward as if you are performing a lunge. Control the deceleration with your forward foot and then push back to the starting position.

Again, focus on landing with good acceptance through both the hip and knee, and maintain good alignment in the pelvis, trunk and knee.

Single Leg Plyometric

Examples include either step up jumps with the same leg or alternating.

A consideration during stage 1 is the surface or environment on which exercises are performed. For example, softer surfaces have shown to reduce peak ground reaction forces and lead to less muscle soreness compared to harder surfaces. 

This means that if you cannot tolerate a given plyometric exercise due to increases in swelling, pain and or excessive muscle soreness, one consideration is performing these in a pool, on sand, a padded surface, or another softer surface in order to help reduce impact forces and thus the load placed through your knee.

Stage 2

Exercises will be moderate intensity bilateral and unilateral plyometrics, with a focus on unilateral deceleration capabilities. 

Criteria to safely progress to stage 2 includes:

• Ability to run on a treadmill with good kinematics for 10 min at 8 km/hour
• Demonstrate good bilateral landing kinematics.
• Demonstrate good single leg squat kinematics.
• You can perform 8 single leg repetitions on a leg press with at least 1.25x bodyweight.
• Possess isokinetic knee extensor and flexor strength >80% of the uninjured side.

Here are some examples of Stage 2 plyometrics:

Bilateral Squat Jump

The squat jump to a box from Stage 1 can be progressed by performing a squat jump in place to maximal height. You will now land from a higher height, resulting in higher impact forces.

Another possible progression is performing a countermovement maximal broad jump. Jump as far as you can forward while landing with optimal movement quality.

Step and Land/Cut

The lunge push back from Stage 1 can be progressed to a forward step and land, and eventually a lateral single leg step and land. Jump from one leg to the other, while demonstrating a controlled landing. Focus on absorbing the landing with good knee and hip flexion angles, as well as maintaining good pelvis, trunk and knee alignment.

Single Leg Plyometric

The step up jumps from Stage 1 can progress to split squat jumps with the same leg or alternating.

Drop Jump Progression 

Additionally, you will want to add in a bilateral drop jump since this is a criteria for entering Stage 3. Start at lower heights and slowly build up to 30 cm, or about 1 foot, as tolerated.

Stage 3

Exercises will be higher intensity and have shorter ground reaction times. The goal with bilateral plyometrics is to build strength, power and rate of force development, while unilateral plyometrics will focus on single leg power, motor control and acceleration.

Criteria to safety progress to stage 3 includes:

• Demonstrate good bilateral drop jump mechanics.
• Demonstrate good single leg landing control.
• Perform 8 single leg repetitions on a leg press with at least 1.5x bodyweight.

Here are some examples of Stage 3 plyometrics:

Bilateral Squat Jump

Bilateral squat jumps from Stage 2 can be progressed to a tuck jump, which will further increase landing intensity.

Another option is rotational jumps which will challenge landing in a different plane of motion.

Step and Land/Cut

The lateral single leg step and land in stage 2 can be progressed by jumping off one leg, landing on the other, and then immediately jumping back to the starting leg. Your goal is to land and jump leaving the ground as quickly as possible.

Another option is performing a step cut at various angles, which will start to combine plyometrics with pre planned running drills. Step and land forward and then cut at pre-planned angles.  Start at 30° and then build up to 45, 60 and eventually to 90°.

Single Leg Plyometric

Split squat jumps from Stage 2 will progress to single leg squat jumps. You can start with single leg squat jumps to a double leg landing or single leg squat jumps to a box in order to reduce landing impact forces. Over time, progress to single leg landings on the floor.

Drop Jump Progression 

The bilateral drop jump from Stage 2 will progress to a single leg drop jump. To start, step off an elevated surface, land on one leg, and then immediately jump onto another elevated surface. Your goal is to land and jump leaving the ground as quickly as possible.

Hops

Finally, another consideration for Stage 3 is adding in single leg hops. Start in place and eventually progress to forward and lateral hops. The goal is to spend as little time on the ground as possible, in order to mimic sport type tasks.

Stage 4

Exercises will consist of very high intensity bilateral and unilateral plyometrics, with the goal of progressing to reactive movements and preparing you for sport-specific training.

Criteria to safely progress to stage 4 includes:

• Possess isokinetic knee extensor and flexor strength >90% of the uninjured side.
• Perform 8 single leg repetitions on a leg press with at least 1.5x bodyweight.
• Demonstrate good movement quality during unilateral landing and deceleration exercises, bilateral and unilateral drop jumps, and while changing directions.

Here are some examples of Stage 4 plyometrics:

Bilateral Squat Jump

Bilateral squat jumps from Stage 3 can be progressed by performing weighted squat jumps.

Step and Land/Cut

The lateral jump from Stage 2 and 3 can be progressed by using a medicine ball. As you jump to the side, the ball will create a perturbation and exaggerate your lateral momentum, making the exercise a challenging reactive drill.

Single Leg Plyometric

Single leg jumps from Stage 3 can be progressed by increasing the height and or distance of each jump. An example is performing single leg forward jumps over hurdles.

Drop Jump Progression 

The single leg drop jump from Stage 3 can be progressed by increasing the height of both surfaces. This will increase the impact force on the initial drop, and then increase the amount of power and strength required to jump onto a higher surface.

Another option is performing a single leg lateral drop jump. Step off an elevated surface to the side, land on one leg and then jump up as quickly as possible.

Programming and Parameters for Plyometric Exercises

The authors provide a general recommendation of gradually increasing volume, or foot contacts, over the 4 stages, starting with 50 and eventually building up to 200 per day of training.

For example, in Stage 1, if you perform a countermovement box jump for 2 sets of 10 reps (2×10=20 foot contacts), same leg step up jumps for 2 sets of 5 reps each (2x5x2=20 foot contacts), and a lunge push back for 2 sets of 5 reps (2×5=10 foot contacts), that would accumulate to 50 foot contacts for that day.

Foot contacts are one way to measure volume, and it is likely worth tracking this daily, weekly and even monthly. Exercises can be performed 2 to 4 days per week.

Disclaimer: These numbers are just a general recommendation, but as I mentioned earlier, you need to monitor your response to exercise, including swelling, pain and or muscle soreness. Find an appropriate starting place and progress over time as tolerated, making adjustments as necessary.

Example Plyometric Progressions

As you move from stage 1 to stage 4, here are some examples of exercise progressions:

Bilateral Squat Jump

• Stage 1: Box Jump
• Stage 2: Maximal Vertical Jump
• Stage 3: Tuck Jump
• Stage 4: Weighted Squat Jump

Drop Jumps

• Stage 1: None (due to higher impact forces and increased capacity requirements, these will start at Stage 2).
• Stage 2: Bilateral Drop Jump (build up to 30 cm height)
• Stage 3: Single Leg Drop Jump to Another Surface
• Stage 4: Single Leg Drop Jump to Another Surface (increase height)

Single Leg Plyometrics

• Stage 1: Step Up Jumps
• Stage 2: Split Squat Jumps
• Stage 3: Single Leg Box Jumps
• Stage 4: Single Leg Hurdle Jumps

Plyometric Exercises Summary

These 4 stages of plyometric exercises can help serve as a guideline during ACL rehabilitation in order to safely return to sport. The authors provide a general framework for exercise progression based on the demands of the task, as well as your capacity to tolerate these demands.

Disclaimer: Plyometric training is only one aspect of ACL rehab. Throughout the process, and in conjunction with these exercises, you should also place an emphasis on lower body strengthening, running, sprinting, on-field sport specific training, and other movement tasks, as outlined by the authors.