## 4 Discussion  
This scoping review aimed to synthesize the scientific evidence on the functional and neuoplastic effects of cross-education (CE) interventions during the rehabilitation after anterior cruciate ligament reconstruction (ACLR). Overall, the results show that CE can play a complementary role in postoperative recovery after ACLR, particularly in the early phases of rehabilitation when direct loading on the affected limb must be limited. Most of the selected studies were randomized controlled trials [17; 18; 23; 45; 46; 47; 48; 50; 51], along with one quasi-experimental study [43], a case study [44] and a systematic review with meta-analysis [24]. These investigations were primarily conducted in young, physically active adults undergoing different ACLR surgical techniques. Generally, the interventions focused on unilateral training of the contralateral limb to assess its influence on muscle strength, balance, functional performance, and neuromuscular activation. Notably, several clinical trials repeatedly reported that CE in ACLR helps preserve or improve quadriceps strength in the affected limb, especially during early postoperative rehabilitation. This finding was observed between weeks 8 and 26 post-surgery in some studies [17; 46; 47; 48; 51; 49]. These interventions involved moderate-to-high-intensity eccentric or  
Figure 5: Visualization map of keyword co-occurrence from studies on cross-education (CE) in rehabilitation, generated with VOSviewer. Each node represents an author keyword; the size of the node reflects its frequency of appearance, while the thickness of the connecting lines indicates the strength of co-occurrence between terms. The color of each node corresponds to a conceptual cluster, allowing visualization of thematic groupings (e.g., strength, neuoplasticity, rehabilitation). This map highlights CE’s strong association with unilateral training, neuromuscular recovery, and emerging interest in cortical excitability, suggesting evolving priorities in the scientific exploration of CE applications. Available online: [[https://tinyurl.com/2485](https://tinyurl.com/2485) baur]([https://tinyurl.com/2485](https://tinyurl.com/2485) baur) (accessed on 27 March 2025). isometric contractions. Similarly, improvements were seen in functional parameters such as limb symmetry, dynamic balance, and postural control, reinforcing CE's potential clinical value as an adjunct tool in neuromuscular recovery. Conversely, discrepancies were noted between studies, particularly those using less intensive protocols or featuring delayed CE implementation. For example, two controlled trials by [PERSON] et al. [49] found no significant effects of CE on neuromuscular function or functional recovery compared to conventional rehabilitation, suggesting that outcomes may largely depend on implementation timing, contraction type, and stimulus intensity, as per the available literature. To evaluate these effects, studies employed a variety of objective and subjective tools. Objective measures included isokinetic dynamometry, surface electromyography, and functional tests such as the Single-Leg Hop Test, Star Excursion Balance Test, and Balance Error Scoring System. Subjective measures included knee function scales like the International Knee Documentation Committee (IKDC) [53], the Knee Injury and Osteoarthritis Outcome Score (KOOS) [54], the Lysholm Knee Scoring Scale (Lysholm) [54], and the Hughston Clinic Knee Scoring System (HCKS) [55]. Additionally, some studies, particularly those conducted in non-ACL contexts, used advanced neurophysiological techniques such as TMS, fMRI, or transcranial direct current stimulation to investigate potential cortical reorganization mechanisms associated with CE. From a functional perspective, most of the included studies reported significant improvements in quadriceps strength of the operated limb, limb symmetry, hamstring-to-quadriceps (H:Q) ratio, postural control, and performance in various functional tests.