Effects of an 8-Week PEP Training Program on Lower-Extremity Kinematics and Injury Incidence During a 90° Cutting Maneuver in Soccer Players With and Without ACL Reconstruction
An 8-week PEP training program significantly improved lower-extremity kinematics during 90° cutting maneuvers in both ACL-reconstructed and healthy soccer players, with greater biomechanical adaptations observed in the reconstructed group, though injury incidence rates remained comparable between groups over a six-month follow-up.
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In the high-speed world of professional soccer, the moment a player plants a foot to change direction is a split-second gamble. This specific movement, known as a cut, places immense stress on the knee, particularly on a band of tissue called the anterior cruciate ligament, or ACL. When this ligament tears, it is a devastating injury that often requires surgery to rebuild the joint. While modern medicine can successfully reconstruct the ligament, returning an athlete to the field is only the beginning of a long journey. Even after a player is cleared to play, their body often remembers the injury. They may move differently, stiffening their legs to protect the healing knee, a strategy that can actually increase the load on the joint and the risk of a second tear. The question facing doctors and trainers is whether specific training can retrain the brain and muscles to move safely again, or if those dangerous habits are permanent.
Researchers set out to answer this by testing a structured training routine on two groups of male soccer players: those who had recently undergone ACL reconstruction and those with healthy knees. The team focused on an eight-week program called Prevent Injury and Enhance Performance, or PEP. This is not a standard gym workout but a specific sequence of stretching, strengthening, and jumping exercises designed to teach the body how to land and turn with better control. The scientists wanted to see if this program could fix the awkward movements that often persist after surgery and, if so, whether those changes would hold up during the actual season. They tracked the players' movements in a laboratory using high-speed cameras before and after the training, and then watched them play for six months to see if injuries occurred.
The results showed that the training worked, and it worked differently for the two groups. Before the program began, the players with reconstructed knees moved with noticeably less bend in their hips and knees compared to their healthy teammates. They also tended to let their ankles roll outward more than necessary. After eight weeks of the PEP program, both groups improved, but the players with the reconstructed knees showed the most dramatic changes. Their knee bending increased by nearly eleven degrees, and their hip bending improved by over eight degrees. Their ankles also stopped rolling outward as much. The healthy players improved as well, but their changes were smaller. This suggests that while healthy athletes already move quite efficiently, those recovering from surgery have more room to grow and can make significant strides in correcting their movement patterns when given the right guidance.
The researchers also kept a close watch on the players for six months after the training ended to see if these biomechanical changes translated into fewer injuries. During this period, the injury rates were remarkably similar between the two groups. The players with reconstructed knees suffered four lower-body injuries, while the healthy group suffered five. Crucially, no one in either group tore their ACL again, nor did anyone tear the ligament in their other knee. While the study was not large enough to prove definitively that the training prevented injuries, the fact that the previously injured group performed just as safely as the healthy group is a promising sign. It indicates that the training helped the recovering players move in a way that is less likely to cause harm, effectively closing the safety gap between them and their uninjured peers.
Despite these successes, the study also highlighted that the job is not entirely finished. Even after the training, the players with reconstructed knees still moved slightly differently than the healthy players, particularly in how they controlled their knees side-to-side. This suggests that eight weeks of training is a powerful start, but it may not be enough to fully restore every aspect of movement to perfect normalcy. The findings support the idea that adding this kind of targeted neuromuscular training to the end of rehabilitation is a smart move. It helps athletes move better and more safely, but it also implies that some players might need even more time or specialized work to fully master the complex mechanics of cutting and turning at a professional level. The path to a full recovery is long, but this research confirms that the right training can significantly lighten the load.
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