Faster Healing and Return to Sport – The Goals of Prehabilitation

After tearing his left ACL, our example patient was scheduled for a meniscus suture with tunnel filling on November 10, followed by ACL reconstruction on February 28. Prehabilitation began in the interim period, with a clear overarching goal: to achieve faster post-operative healing and, consequently, a quicker return to sport.

EMG Training Therapy in 4 Phases

To achieve the goal of a faster recovery and return to sport, the therapy was structured around four clearly defined milestones. The first phase focused on reducing pain and swelling. This is a crucial foundation for any subsequent therapeutic measures and must be achieved before progressing further. The second phase aimed to improve the patient’s range of motion. Restoring mobility in the affected joint is essential to enable more active interventions later in the therapy. The third phase marked the transition into active rehabilitation in the clinical setting. Here, the focus was on promoting muscle activity and, at the same time, identifying any emerging deficits. The goal was to prevent the development of dysfunctional compensation patterns, which often arise when certain muscles become overactive in response to injury-related inhibition. The fourth phase addressed compensations that may already have established themselves due to the trauma or injury. This step was designed to reduce or eliminate those patterns by actively retraining correct movement strategies. Throughout all four phases, particular emphasis was placed on stabilising the leg axis through targeted EMG-guided training interventions, ensuring that neuromuscular control could be restored efficiently and sustainably.

The Role of the Gluteus Medius as a Key Stabiliser

To meet these goals, various muscle groups were analysed and specifically trained, starting with the gluteus medius, a critical stabiliser for sagittal plane control. Despite its importance, it is often underused and compensated by other muscles. Even with crutches, EMG mapping allowed testing of the patient’s conscious activation of the muscle. Interestingly, the injured left side showed slightly better values than the right, though both were too low. This is commonly linked to trauma- or surgery-induced inhibition, which can cause even unaffected muscles to shut down.
Through EMG biofeedback training, targeted gluteus medius activation was trained across different rotation angles. This prevented full muscular shutdown. Over the four-month period, these exercises significantly improved activation on both sides and reduced compensatory overuse of other muscles.

Screening 2: Vastus Medialis and Lateralis

In the second session, focus shifted to the vastus medialis and vastus lateralis. The goal wasn’t comparing left vs. right, but rather examining the balance between the two on the same leg. Since it was expected that the injured leg would show overall reduced activity, this offered deeper insights. Various positions were tested to control for hamstring influence: straightening the left knee, seated or lying extensions, and bilateral squats. The mapping showed symmetrical muscle activity in open-chain movements, but a clear inhibition of the vastus medialis during loaded phases. 

Counteracting Vastus Medialis Inhibition

Because the vastus medialis tends to atrophy quickly, it was crucial to monitor and counteract this inhibition. The common approach (terminal knee extension with external rotation) activates both vastus medialis and lateralis, which can create imbalances.
To favor vastus medialis recruitment, exercises were chosen that enhanced medial activity, such as holding an isometric knee angle combined with hip flexion.
Using the myoact app, progress curves showed a 90% improvement in symmetry and a significant increase in vastus medialis activation during squats. Overall muscle activity rose from 150 to 400 microvolts. 

Peroneus and Foot Mechanics

Patients with ACL injuries often lose the ability to consciously activate the peroneus or to form a stable foot arch. This was also true for our patient. While the healthy right foot responded well to instructions, the injured left side struggled. To address this, various movement patterns were used to counter valgus stress (the inward force on the knee often worsened by foot instability). Movements performed successfully on the right side were mimicked on the left using motor control training with knee stabilization instructions. Later, integrated exercises were introduced, such as side planks, that combined peroneus and gluteus medius activation.

Interpretation

Multiple studies support the importance of prehabilitation in ACL injury recovery. Training and therapy before surgery can significantly reduce the post-operative time required to return to sport. A key metric here is the Lower Limb Symmetry Index (LLSI), which should remain below a 20% strength difference between legs. In our example, a difference of only 10% was achieved pre-surgery in knee extension strength. However, a current challenge in prehabilitation is the lack of consensus on its content, duration, and frequency. This is where EMG and myoact come into play. EMG provides objective data about inhibitions, compensations, and mind-muscle disconnects. This enables highly personalised therapy that can be adapted between sessions based on the patient’s real-time status. 

Conclusion

For optimal ACL surgery preparation, stabilising the leg axis was the initial goal, achieved here through targeted training of the gluteus medius, vastus medialis, and peroneal muscles. This prehabilitation built the foundation for post-surgical rehabilitation. Even under low loads, previously trained activation patterns could be accessed, accelerating strength gains and functional recovery. By providing objective data on a patient’s neuromuscular status, EMG helps optimize training strategies – supporting faster healing and a more sustainable return to sport.