Blood Flow Restriction Training Prior to and After Anterior Cruciate Ligament Reconstruction: A Scoping review

Blood Flow Restriction Training Prior to and After Anterior Cruciate Ligament Reconstruction: A Scoping review | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Systematic Review Blood Flow Restriction Training Prior to and After Anterior Cruciate Ligament Reconstruction: A Scoping review Roger Fontanet Claret, Rafel Donat Roca, Eduardo Carballeira This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6062247/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background Anterior cruciate ligament injuries often lead to muscle atrophy and prolonged recovery following anterior cruciate ligament reconstruction (ACLR). Blood flow restriction (BFR) has emerged as a strategy to optimize neuromuscular adaptations with lower loads, potentially enhancing rehabilitation outcomes in both preoperative and postoperative phases. This review aims to comprehensively evaluate the comparative effectiveness of BFR applied during resistance and endurance exercises versus non-BFR protocols, both before and after ACLR, while also examining key training parameters and BFR protocols to guide further research and clinical practice. Literature search A comprehensive literature search was conducted across multiple databases, including WoS, PEDro, Scopus, PUBMED (MEDLINE), SportDiscus, and the Cochrane Library, covering publications from inception to January 22, 2025. Studies eligible for inclusion were randomized controlled trials and quasi-randomized controlled trials that compared BFR interventions with non-BFR training in patients undergoing ACLR. Data synthesis followed the Preferred Reporting Items for Systematic Reviews and Meta-analysis extension for Scoping Reviews. The PEDro and CERT scales were used to assess the methodological quality of the included studies. Detailed training parameters and cuff specifications were extracted and summarized in tables. Results Fifteen of the initial 385 articles identified met the eligibility criteria and were included in the final analysis, comprising a sample of 417 patients. Outcomes were categorized into six areas: body composition, neuromuscular responses and adaptations, self-report questionnaires, functional measures, muscle physiology and biomarkers, and return to activity. Five articles focused on preoperative interventions, nine on postoperative interventions, and one addressed both phases. Conclusion This review suggests that BFR resistance training is an effective tool in the preoperative and postoperative phases of ACLR. Additionally, it can help improve muscle size, strength, functional measurements, body composition, muscle blood flow, and subjective perceptions. Physical Medicine & Rehab Sports Medicine and Kinesiology Anterior cruciate ligament reconstruction blood flow restriction preoperative rehabilitation postoperative rehabilitation exercise parameters Figures Figure 1 Figure 2 INTRODUCTION The occurrence of anterior cruciate ligament (ACL) injuries has tended to increase, notably affecting adolescent athletes( 1 – 4 ) and the general population.( 5 ) The annual incidence is estimated to be approximately 0.01–0.05% in the general population, 0.15 to 7.32% in professional athletes, and 0.002 to 1.62% in amateur athletes.( 6 ) Over the past few decades, there has been a significant increase in ACL injuries among young athletes, with increases ranging from 44–143%.( 4 , 7 , 8 ) ACL injury directly impacts the quality of life of injured individuals and has a high socioeconomic impact in both the short and long term.( 9 ) In the early stages following ACL reconstruction (ACLR), prescribed immobilization, restricted weight bearing, intraoperative tourniquet, and the inability to perform heavy load resistance training (HL-RT) and/or high-intensity endurance exercises collectively contribute to muscular atrophy and weakness in the lower extremities.( 10 , 11 ) This particularly affects the quadriceps, which is a clinical manifestation and primary risk factor for the development of knee osteoarthritis,( 12 ) and leads to deconditioning in the injured individual, thereby delaying their return to activity. Muscular strength and hypertrophy are primarily induced through heightened firing rates and enhanced recruitment of motor neurons, thereby resulting in increased mechanical tension within the engaged myofibers.( 13 , 14 ) Optimal development of maximal strength and power is achieved by employing heavy loads (≥ 85% of one repetition maximum, 1RM) and moderate loads (40% − 70% 1RM), respectively.( 15 ) However, traditional muscle-strengthening training involving near-maximal loads or engaging in contractions at maximum voluntary velocity is not recommended during the initial stages following ACLR.( 16 ) Consequently, there has been a growing interest in blood flow restriction (BFR) applied to proximal limbs during exercise as a potentially effective method for inducing neuromuscular, vascular and metabolic adaptations with lower intensities than typically needed.( 17 , 18 ) This technique has demonstrated the ability to enhance skeletal muscle fiber growth and neural function,( 19 ) as well as long-term changes in mitochondrial and microvascular adaptations.( 20 ) Such adaptations could offer benefits in both the preoperative (PRE-OP) and postoperative (POST-OP) phases of ACLR while also providing a peripheral stimulus to improve cardiovascular fitness,( 17 ) which is often diminished after ACLR rehabilitation compared with preinjury values. ( 21 ) Blood flow restriction resistance training (BFR-RT) and BFR endurance training (BFR-ET) have emerged as promising alternative to traditional HL-RT or high-intensity training; these methods yield comparable neuromuscular adaptations( 19 , 21 ) and offer benefits such as alleviating knee pain, reducing swelling, and improving functionality.( 22 , 23 ) Furthermore, BFR-RT has been implemented in PRE-OP phases to confer protective effects against ischemia-induced injury and bolster muscle strength and endurance for faster rehabilitation.( 24 – 26 ) On the other hand, BFR-RT applied during the POST-OP phases enhances skeletal muscle hypertrophy and functional measurements to a similar extent as HL-RT.( 27 ) Furthermore, BFR-ET during the POST-OP phase resulted in reduced moments around the knee joint compared with the no-BFR condition, suggesting that BFR-ET is a safe option to utilize following ACLR.( 28 ) Therefore, we conducted a scoping review to comprehensively explore existing research, establish terminology, identify potential pathways for targeted design of future interventional studies, and pave the way for the application of BFR in clinical practice.( 29 , 30 ) The current review aimed to address the following research questions: 1) What are the effects of BFR-RT or BFR-ET compared with other training protocols without BFR, both PRE-OP and POST-OP, in patients undergoing ACLR; 2) What are the commonly used training and BFR parameters during BFR-RT and BFR-ET protocols, both PRE-OP and POST-OP, in patients undergoing ACLR. METHODS Protocol and Registration We conducted a scoping review to explore the effects of BFR training on ACL injury and identify areas where further research is needed( 31 ). We aimed to understand the responses and adaptations induced by BFR in the neuromuscular, peripheral vascular, and peripheral metabolic systems. This review followed the recommendations from the PRISMA applied to exercise, rehabilitation, sports medicine, and sports science.( 32 ) We registered the present review in Open Science Framework (April 1 2024; DOI : 10.17605/OSF . IO/76243; https://osf.io/76243/?view_only=d944754ee6404bc19fa4d7addc950d54 . Eligibility criteria The PICOS approach guided the selection of eligible sources, with inclusion criteria outlined in Table 1 , which required articles to be peer-reviewed original research, available in full-text format, no language restrictions were applied. Table 1 Inclusion and exclusion criteria based on the PICOS strategy Inclusion criteria Exclusion criteria Population Human healthy patients affected by a primary ACL injury with or without concomitant meniscal procedures and surgically intervened with patellar, quadriceps, or hamstring tendon autograft were included. Previous ACL injury, additional knee impairments, or multiple reconstructive procedures. Intervention Interventions that combined BFR and resistance exercises or endurance exercises applied during PRE- and/or POST-OP phases. The duration of the intervention should be at least one week for both PRE- and POST-OP. Analyses were not conducted independently for interventions combining BFR with techniques such as electrostimulation or other modalities, or the duration of the interventions were lower than required in the inclusion criteria. Comparator Comparison group performing resistance exercises or endurance exercises with or without BFR or a placebo (i.e., sham BFR). There is no control/comparison group. Articles that do not contain a comparative analysis with control/comparison groups without BFR during exercise interventions, or a placebo (i.e., simulated BFR). Outcomes Validated assessment analyzing muscular structural changes, muscle strength, neuromuscular adaptations and responses, functional changes, self-report questionnaires, pain, peripheral vascular and local metabolic parameters. No reported validated tests providing quantitative values. Study design Randomized controlled trials or quasi-randomized controlled trials with pre-post measurements of one or more outcomes, comparing BFR to a control or comparison group. Opinion articles, editorials, systematic reviews, case-control studies, case series studies, conference abstracts, in-progress articles, cohort articles, cross-sectional articles, and studies with results obtained without an initial evaluation. ACL, anterior cruciate ligament; BFR, blood flow restriction; PRE-OP, preoperative; POST-OP, postoperative; QRCT, Quasi-randomized controlled trial; RCT, Randomized controlled trial. Strategy of Search and Databases Systematic literature searches were carried out in three phases. In the first phase, SWIFT-reviewer( 33 ) was utilized for the initial exploratory search. Specific keywords such as BFR and ACL were employed to delve into, categorize, and determine the terms to utilize. In the second phase, primary searches were conducted on various databases, including Web of Science (WoS), PEDro, Scopus, PUBMED (MEDLINE), SportDiscus, and Cochrane Library databases, from inception until 22-01-2025. The search formula was adapted according to the specifics of the respective database and contained a combination of terms related to BFR and ACL injury. The search fields, filters, and results from the electronic database can be found in supplemental appendix A. In the third phase, we introduced the eligible articles from the second phase into the Citation Chaser.( 34 ) This web platform was used to find potential articles in forward (articles that cited the eligible articles) and backward (references within the eligible articles) citation chasing in the literature. Additionally, a search in the grey literature was conducted using platforms such as OpenGrey, OAlster, and Google Scholar to ensure comprehensive coverage of relevant studies and reports not found in traditional academic databases. The authors were also contacted when supplementary material for specific articles was unavailable. Selection of Sources of Evidence and Data Extraction The selection and screening process was conducted via Rayyan.( 35 ) Two independent reviewers (XXX and XXX) screened the titles and abstracts of the articles via a blinded platform( 35 ) to assess their eligibility according to inclusion and exclusion criteria, both in the first and second phases of the search. An experienced supervisor (XXX) was blinded to resolve conflicts in the screening process. The articles that passed the title and abstract screening were entered into the Citation Chaser platform( 34 ) for exhaustive tracking of backward and forward citations. Finally, the screening process was repeated for full-text review. The data extraction from the selected studies was conducted by two reviewers (XXX and XXX), and conflicts were discussed by two supervisors (XXX and XXX). Risk of Bias, Quality of Evidence, and Quality of Exercise Reporting The methodological quality of the RCTs and QRCTs was evaluated via the Physiotherapy Evidence Database (PEDro)( 36 ) bias detection tool, which evaluates eleven specific criteria. The Consensus on Exercise Reporting Template (CERT)(37) was used to evaluate whether the reviewed articles provided a structured framework and effectively documented and reported exercise outcomes and parameters. The results are presented in supplemental appendix C. Two evaluators conducted all assessments, and a third reviewer resolved any possible conflicts. Data Items and Synthesis of Results The study variables were categorized into six sections: body composition (including muscle volume, thickness, cross-sectional area and changes in site-specific bone mass, bone mineral density, whole limb lean mass); neuromuscular adaptations and responses (including maximum voluntary isometric contraction, isokinetic strength, activation of vastus medialis, central activation ratio of knee extensors, and fatigue indexes); functional measurements (including all tests and values related to functionality); self-report questionnaires (including patient-reported scales and questionnaires); muscle physiology and biomarkers(including muscle biopsy analysis and blood sample analysis); and return to activity time. The results were systematically categorized and summarized into key thematic areas, and the evidence was presented in a narrative format and complemented by tables. RESULTS Study characteristics and strength of recommendations Literature searches conducted across six different databases yielded 385 articles. After removing 74 duplicate articles and applying selection criteria to 311 articles based on title and abstract, 268 articles were excluded. A comprehensive assessment of the full texts of 33 articles was subsequently conducted, which led to the exclusion of eighteen articles: seven were excluded because of the wrong article type, another seven were omitted due to inaccuracies in outcome measurement and registration, and the remaining four were discarded because of an incorrect study design. In addition to the main search, a backward and forward citation chase identified 1,594 articles, and a grey literature search yielded 1,630 articles. Fifteen articles were assessed for eligibility, but all were duplicates of those found in the main search. Finally, a total of 15 studies were included in the present review. Twelve were randomized controlled trials,( 38 – 46 ) and the remaining three were quasi-randomized controlled trials.( 47 – 49 ) The details of the charting process, with the specific reasons for exclusion, can be seen in Fig. 1. The overall number of articles selected demonstrated a low risk of bias according to the PEDro( 36 ) scale, as shown in Fig. 2 , with a median score of 6,87 out of 10 for all included RCTs and QRCTs. The lowest score recorded was 6, indicating an acceptable level of quality, whereas the highest score achieved was 9, reflecting excellent quality. Most of the selected studies exhibited bias regarding blinding of all subjects (80%) and all therapists (86,67%). The PRE-OP articles met the specified criteria of the CERT(37) scale in 51,6% of the cases, whereas the POST-OP studies met it in 60,8% of the cases (supplemental appendix C). The final analysis included 417 patients who underwent ACLR (285 males and 132 females). All studies utilized BFR-RT as the experimental intervention, with one applying a cross BFR education protocol to the uninjured leg( 50 ), and none employing BFR-ET. Five studies used BFR-RT during the PRE-OP phase( 46 , 47 , 49 , 51 ) nine were conducted POST-OP phase ( 40 – 45 , 50 , 52 ) and one study was performed in both the PRE- and POST-OP,( 53 ) which was discussed in the POST-OP results due to its longer follow-up and more extensive control during that phase. The general characteristics of included studies (time of intervention, author, study design, autograft type, intervention time, population, sample characteristics, groups, and studied variables) are shown in Table 2. The CERT scale(37) was employed to ensure comprehensive reporting of exercise parameters (supplemental appendix C), while the distribution of studies based on the FITT-VP parameters,( 54 ) describing exercise variables such as frequency, intensity, time, type, volume, and progression, is detailed in supplemental appendix D. Various training protocols were employed, with training loads ranging from body weight to 70% of 1 repetition maximum and training intensity was predominantly determined by calculating the percentage of 1 repetition maximum. ( 40 – 43 , 47 – 49 ) Intermittent( 43 , 44 , 46 ) and continuous( 38 , 40 – 42 , 45 , 50 ) rest periods were utilized, with various tools employed for calculating limb occlusion pressure (LOP). No adverse events were reported during interventions( 38 , 40 – 42 , 45 , 46 ). Specific training parameters and cuff details for individual studies are outlined in Table 3. Outcome Measures Body composition The PRE-OP interventions demonstrated improvements( 47 ) or comparable( 38 , 46 ) results in quadriceps cross-sectional area (CSA) between BFR-RT groups and comparison groups. In POST-OP studies, BFR-LL demonstrated comparable CSA effects to HL-RT at 70% 1RM,( 41 , 45 , 53 ) yet combining BFR with HL (BFR-HL) yielded no additional benefits.( 43 ) While combining BFR-RT with home-based intervention with body-weighted isometric protocols appeared ineffective.( 44 ) Jack et al.( 42 ) observed a protective effect of BFR-LL against POST-OP bone loss, in contrast with the significant declines in lean mass observed in the comparison group. Neuromuscular adaptations and responses PRE-OP interventions significantly improved knee extensor peak torque( 38 , 47 ) or yielded similar results( 46 , 49 )( 38 , 46 ).( 47 , 49 ) A PRE-OP research team made significant progress in their studies,( 47 – 49 ) consistently achieving favorable outcomes within the BFR-LL group and effectively preventing the deterioration of maximal muscle strength and knee extensor endurance. Hughes et al.( 41 ) POST-OP study compared BFR-LL at 30% and HL-RT at 70%. At 8 weeks, both groups showed similar increases in scaled 10RM strength and similar decreases in knee extension peak torque. However, HL-RT group presented significantly greater decreases in knee flexion peak torque at all speeds compared to BFR-LL group. This was accompanied by a strong effect size, suggesting a more detrimental effect for HL-RT. Vieira et al.( 45 ) utilized similar groups and reported that compared with HL-RT, BFR-LL resulted in significantly greater improvements in muscle strength within a shorter rehabilitation period while Curran et al.( 43 ) demonstrated that HL-RT alone resulted in significant improvements in quadriceps muscle strength, without any additional benefit from incorporating BFR to HL-RT. Additionally, Erickson et al,( 53 ) showed that BFR-LL was equally effective as sham BFR group combined with HL-RT in their PRE- and POST-OP study. Ultimately, Sevinc( 50 ) found a significant main effect of time on quadriceps strength in both the involved (p < 0.001) and uninjured limbs, with no additional gains from adding BFR to cross-education in post-ACLR patients. Self-report questionnaires Self-report questionnaires were assessed in seven studies to evaluate knee pain, muscle pain, rate of perceived exertion, knee function, knee symptomatology, and self-perceived depression.( 38 – 41 , 43 , 45 , 46 ) Home-based PRE-OP interventions yielded similar( 46 ) or improved( 38 ) outcomes between BFR-LL and LL-RT. However, in POST-OP interventions, BFR-RT consistently improved knee joint pain and self-reported outcomes in studies comparing BFR-LL vs HL-RT,( 40 , 41 , 45 ) except for muscle pain immediately following each set of exercise,( 40 ) where the BFR-LL group had worse values than the HL-RT group. Additionally, the study of Khalil et al.( 39 ) compared BFR-LL vs LL-RT and another study comparing BFR-HL (70% 1 RM) vs HL-RT( 43 ) did not yield significant improvements. Functional Measurements Three PRE-OP studies investigated functional measurements but did not find significant improvements in knee ROM( 38 , 46 ) or Y-balance tests( 49 ). However, in contrast, POST-OP interventions demonstrated significant results. Hughes et al( 41 ) reported significant improvements in Y-balance on the injured leg across all directions (anterior, posteromedial, and posterolateral), with the BFR-LL group exhibiting a strong effect size compared with the HL-RT group. Additionally, in the study by Jack et al.,( 42 ) significant improvement in Y balance was observed only in the BFR-LL group between 8 and 12 weeks compared with the LL-RT group. Additionally, Hughes et al.( 41 ) demonstrated significant improvements in mid-patellar knee joint circumference and knee range of motion (ROM), with no observed changes in knee laxity in the BFR-LL group. Muscle Physiology and Biomarkers In the PRE-OP study by Žargi et al.( 49 ) significant improvements in muscle blood flow were observed at week 4 POST-OP in the BFR-LL group (↑52%) compared with the SHAM-BFR group (↓37%), with a notable interaction detected between time and group factors in muscle blood flow. Additionally, Kacin et al.( 47 ) conducted a biopsy analysis, emphasizing the role of hypoxia-inducible factor 1-alpha (HIF-1α) in cellular adaptation to hypoxia. These authors reported higher mRNA levels of VEGF-A, which is crucial for angiogenesis regulation, in the BFR-LL group than in the SHAM-BFR group. Regarding the POST-OP phase, one study( 52 ) examined key biomarkers related to muscle atrophy following ACLR through blood samples. The results showed significant reductions in serum Atrogin-1 (↓-12.53%) and serum MuRF1 (↓-15.47%) from week 0 to week 12 in the BFR-RT group compared to the RT group, with a significant group x time interaction for Atrogin-1 and a significant time effect for both biomarkers (p < 0.05). Return to activity time Jack et al.( 42 ) demonstrated a significant reduction in the time to return to sports by 1.4 months, accompanied by a strong effect size, in a 12-week rehabilitation protocol when BFR-LL was compared with LL-RT. Curran et al.( 43 ) found no significant differences between BFR-HL and HL-RT. Exercise Parameters and Reporting Standards The CERT scale(37) was used to evaluate the practical implementation and completeness of exercise reporting across the included studies. In our analysis, adherence to the CERT criteria was 51.6% for PRE-OP interventions and 60.8% for POST-OP interventions. Notably, compared with PRE-OP studies, POST-OP studies achieved equal or better results for 13 of the 19 evaluable criteria. Both PRE-OP and POST-OP studies presented low scores in detailing how adherence to exercise is measured and reported (PRE-OP: 0% vs. POST-OP: 42.9%). In contrast, both types of articles provided a detailed description of each exercise to enable replication (PRE-OP: 100% vs. POST-OP: 88.9%). PRE-OP studies accounted for the detailed description of any home program component in 100% of cases, whereas POST-OP studies did so in 55.6% of cases. Finally, 77.8% of POST-OP studies explained how exercises are tailored to the individual, whereas none of the PRE-OP studies reported this. One article that examined both the PRE- and POST-OP phases achieved favorable results in 13 of the 19 criteria. To prevent influencing the outcomes, the study was analyzed separately for each phase. The reporting of exercise parameters on FITT-VP( 54 ) framework revealed variability between studies in both phases (supplemental appendix D). PRE-OP studies included short-duration interventions, averaging 1.91 weeks with 5–10 sessions. In contrast, POST-OP studies utilized longer protocols, all studies with 16 or more sessions, with an average intervention duration of 9 weeks. Additionally, the study that examined both PRE- and POST-OP ACLR phases had a duration of 24 weeks, the longest among all those analyzed. A total of 9 studies from the review utilized personalized exercise protocols. (PRE-OP: 2/5 vs POST-OP: 6/9 vs PRE and POST-OP: 1/1), whereas the remaining studies focused predominantly on specific exercises (PRE-OP: 3/5 for leg extension vs POST-OP: 3/9 for leg press). Regarding repetitions, adherence to the “30-15-15-15” protocol was noted in 40% of PRE-OP studies compared with 55.5% of POST-OP studies. Additionally, the remaining PRE-OP studies aimed for repetitions to failure, whereas the POST-OP studies that did not follow the “30-15-15-15” protocol adhered to different repetition patterns, similar to the study that examined both phases and followed its rehabilitation plan. Among the studies reviewed, 66.7% determined the optimal exercise load by one repetition maximum. Training loads for the BFR-RT group ranged from body weight to 30% of 1RM, exceptuating two studies that employed 70% of 1RM. Progression of training stimulus was reported in 2/5 of PRE-OP interventions compared with 8/9 of POST-OP studies and PRE- and POST-OP study 1/1. DISCUSSION In this scoping review examining the application of BFR-RT before and after ACLR, no study reported that BFR-RT was less effective than the comparison group in any outcome measure, except for one specific study where knee pain during training sessions was greater in the BFR-LL group compared to the HL-RT group. Specifically, 2/5 of PRE-OP studies showed superior outcomes in BFR-RT interventions compared to groups trained with the same or different loads. In POST-OP interventions, 5/9 studies showed superior results for BFR-RT, with the remaining studies finding comparable outcomes between the BFR-RT and comparison groups. None of the studies included BFR-ET, highlighting the need for future research on its effectiveness in ACLR rehabilitation. Based on the evidence reviewed in PRE and POST-OP phases of ACLR, BFR-RT shows promise as a useful interim step.( 55 ) The results of our review regarding body composition, neuromuscular adaptations, muscle physiology and biomarkers, and self-report questionnaires are consistent with those reported in other systematic reviews studying the effects of BFR on ACLR.( 56 – 58 ). Furthermore, we emphasized rigorous methodological evaluation via the PEDro scale.( 36 ) Additionally, we employed the CERT scale(37) to assess the quality of reporting exercise parameters. These tools are crucial for extracting reliable information related to exercise parameters and methodology, ensuring that study results are applicable in practical settings. On the other hand, previous reviews have incorporated non-randomized trials and studies with a high risk of bias( 26 , 27 , 59 , 60 ), which can affect the reliability of the findings. To avoid such biases, we included only RCTs and QRCTs in our review. Our review stands out from previous reviews because of its emphasis on precise article selection criteria, the inclusion of high-quality trials, and the meticulous extraction of information concerning exercise parameters and BFR methodology. This is the first systematic review that specifically evaluated the use of BFR combined with exercise during the PRE-OP and POST-OP in ACLR patients. PRE-OP interventions were specifically designed to explore the effects of BFR-RT on muscle preservation, strength maintenance, and overall PRE-OP outcomes. Factors such as immobilization, restricted weight bearing, intraoperative tourniquet and nerve block administration during ACLR surgery may contribute to quadriceps weakness.( 11 ) This weakness can impact functionality, ( 61 , 62 ) quality of life,( 11 ) and joint health over time.( 63 ) In other reviews, exercise-based prehabilitation has been shown to be favorable for ACLR,( 64 , 65 ) whereas adding BFR to prehabilitation appears promising.( 26 ) However, Žargi et al.( 49 ) The initial study implemented BFR-LL with knee extension exercises for 10 days PRE-OP but reported no significant POST-OP effects compared with LL-RT in terms of maximum voluntary isometric contraction and CSA of knee extensors. Other studies highlighted that quadriceps endurance, rather than maximal strength and CSA, emerged as the most significant predictor of quadriceps atrophy following ACLR.( 66 , 67 ) Following the PRE-OP protocol established in the study by Zargi et al. ( 48 ) , two new studies( 47 , 49 ) selected different outcomes while maintaining the original intervention protocol. A statistically significant group interaction was detected at week 4 POST-OP, with near-infrared spectroscopy and muscle surface electromyography activation.( 48 ) The second PRE-OP study highlighted statistically significant improvements in muscle fatigue index.( 47 ) At 3 weeks POST-OP, the BFR-LL group presented a 60% decrease in peak torque at 60°/s, whereas the LL-RT group presented a 21% decrease. The previous results confirm findings in other systematic reviews,( 68 ) were improvements related to muscle endurance and blood flow muscle parameters may prevent ischemia‒reperfusion damage and protect against muscle protein oxidation,( 68 , 69 ) and consequently, these improvements may serve as a safeguard against the threat of POST-OP quadriceps atrophy. 26 Moreover, the PRE-OP study of Kacin et al.( 47 ) conducted muscle biopsies in ACLR patients and obtained a significant impact of BFR-RT on vascular endothelial growth factor-A (VEGF-A) and mRNA levels, which are crucial for angiogenesis.( 68 ) These results align with trends from other reviews based on the general population.( 68 , 69 ) Identifying effective strategies to increase muscle endurance could optimize both PRE and POST-OP results. POST-OP interventions using BFR-RT are typically implemented in the early phases after ACLR. These interventions aim to investigate the impact of BFR-RT on muscle recovery, strength restoration, and overall POST-OP rehabilitation in individuals who have undergone ACLR. Specifically, improvements in muscle volume, a key aspect of body composition, were observed and align with findings from other systematic reviews, highlighting the potential of BFR-RT in enhancing muscle recovery and rehabilitation outcomes.( 11 , 27 ) BFR-LL has been demonstrated to be superior to LL-RT( 42 ) and comparable to HL-RT( 41 , 45 ) in enhancing muscle volume. Moreover, BFR-HL versus HL-RT yielded similar results;( 43 ) notably, BFR-HL may deviate from the fundamental physiological principles of BFR-RT, as it involves HL-RT rather than the LL approach typically used in BFR-RT. Additionally, a POST-OP study( 52 ) analyzed two key biomarkers of muscle atrophy, Atrogin-1 and MuRF1, which are typically elevated in response to disuse. The study found significant reductions in serum Atrogin-1 (↓12.53%) and MuRF1 (↓15.47%) levels in the BFR-RT group compared to RT, suggesting that BFR may help mitigate muscle protein degradation and prevent atrophy. Parameters related to bone mineral density were examined in the study by Jack et al.( 42 ) These significant findings align with the meta-analysis by Wang et al.( 70 ) highlighting that BFR-LL training results in greater improvements in bone health than does LL-RT.( 71 ) Better bone mineralization may enhance graft integration in ACLR procedures and help prevent conditions such as osteopenia and osteoporosis in specific patients, making this a relevant line of investigation for future research. A previous meta-analysis( 72 ) focusing on non-injured populations demonstrated that, compared with BFR-LL, HL-RT leads to greater muscle strength gains. However, our review revealed that compared with HL-RT, BFR-LL or BFR-HL interventions produce similar or superior muscle strength 42,44,46 in ACLR patients. ( 41 , 43 , 45 ) Additionally, a study combining BFR with isokinetic training and cross-education on the uninjured leg found no additional benefits from adding BFR, as both groups achieved similar results.( 50 ) Comparing BFR-RT to approaches such as BFR-HL or BFR with isokinetic training may have deviated from the fundamental physiological principles of BFR-RT. Moreover, some of these studies concluded that BFR-LL was ineffective simply because it produced similar outcomes to HL-RT, overlooking the fact that achieving comparable results with significantly lower loads is, in itself, a meaningful finding. This misinterpretation may stem from methodological choices, particularly the use of HL-RT 'sham groups' and the selection of comparators, which could have influenced the perceived effectiveness of BFR. During the early to middle stages POST-OP ACLR, BFR-RT has emerged as an effective strategy, particularly when HL-RT may cause pain or when limited mobility or high-load intolerance is present. Knee pain is a key outcome of ACLR and BFR-RT research. BFR-LL has been shown to facilitate a more rapid reduction in knee pain than HL-RT does, which is correlated with improved functionality and quality of life.( 40 , 41 , 45 ) The physiological mechanisms behind BFR-RT induced pain reduction are not fully understood, but several theories have been proposed. These include activation of the opioid and endocannabinoid systems, increased activation of the descending inhibitory pathway, early preferential recruitment of high-threshold motor units (Type II), and conditioned pain modulation, where pressure and discomfort during BFR-RT may act as conditioning stimuli.( 71 , 73 , 74 ) However, further research is needed to fully understand and validate these mechanisms to establish viable pain management protocols. In our review, home-based BFR rehabilitation unsupervised exercise protocols( 38 , 44 , 46 ) generally demonstrated less significant improvements than supervised protocols did.( 39 – 43 , 45 , 47 – 49 ) This contrasts with findings from other reviews that combine exercise without BFR, suggesting that supervision and location do not directly determine final outcomes in ACL rehabilitation.( 75 – 77 ) Self application of BFR cuffs requires precise pressure settings and effective discomfort management, which may impact adherence and treatment effectiveness. Identifying key factors that enhance home-based interventions could be pivotal in optimizing their efficacy and reducing the socioeconomic costs associated with ACLR rehabilitation. When evaluating the practical implementation and training parameters in experimental interventions via CERT scale(37), we identified a significant disparity. This inconsistency arises from the lack of a standardized framework for describing exercise parameters (FITT-VP)( 54 ) and BFR-RT methods. PRE-OP interventions for ACLR adhered to CERT criteria in 51.6% of the parameters, whereas POST-OP interventions followed them in 63.9%. This difference likely reflects a more developed research line in the POST-OP phase. However, PRE-OP interventions are being increasingly investigated,( 78 ) with a focus on short-term adaptations to mitigate iatrogenic atrophy from the injury and surgery, ultimately aiming to "prepare the leg for the storm”.( 65 ) This contrasts with the longer interventions reported in POST-OP phases. The shorter duration of PRE-OP interventions may be associated with the limited time before surgery, which is often scheduled within weeks.( 79 ) Although consensus on specific prehabilitation protocols for BFR-RE and ACLR remains limited, emerging research suggests that extended prehabilitation could lead to improved long-term outcomes in certain cases.( 80 ) Notably, all PRE-OP studies incorporated open kinetic chain (OKC) exercises, whereas POST-OP studies predominantly utilized closed kinetic chain (CKC) exercises. This could be due to some articles suggesting that OKC exercises, such as single-leg extensions, may place significant strain on the ACL graft because of the lack of co-contraction between the quadriceps and hamstrings, potentially resulting in excessive anterior shear forces on the knee joint.( 81 , 82 ) Meta-analyses indicate no definitive superiority between open and closed kinetic chain exercises after ACL reconstruction regarding knee laxity and overall outcomes.( 82 , 83 ) In both open and closed kinetic chain exercises, load progression is crucial for effective rehabilitation. The reviewed articles suggest that BFR-LL may be beneficial in early ACLR phases, providing a safe way to increase loading. Given the pivotal role of exercise parameters in optimizing rehabilitation outcomes, the notion that exercise functions as medicine highlights the necessity of understanding its appropriate dosage and administration.( 84 ) The lack of replicability in exercise parameters observed in our review is not unique; other reviews involving diverse pathologies( 85 ) or PRE-OP ACLR patients( 27 , 86 ) have shown similar inconsistencies. Reporting these parameters is crucial for enhancing the replicability and transferability of findings to clinical practice. Consistent with the overall lack of reporting, none of the studies in our review that reached muscular failure reported on effort intensity relative to muscle failure proximity. This omission has physiological implications, as effort intensity can significantly influence physiological responses and adaptations. The studies included in our review yielded results such as systematic reviews examining training for muscular failure, which increases metabolic response, muscle damage, and perceived exertion while decreasing biomechanical properties.( 87 , 88 ) Nonetheless, this approach provides gains in strength and muscle size comparable to non-failure training. Notably, applying BFR-LL to volitional failure yields similar results to LL-RT, but BFR-LL leads to earlier failure than does LL-RT,(45,89) reducing session volume(90) and duration. This makes BFR-LL a valuable option when reaching failure, which is an objective during rehabilitation stages. With respect to fatigue, intermittent BFR-RT has demonstrated strength gains comparable to continuous application but with reduced fatigue.(91,92) However, only one study utilized intermittent BFR-RT.( 43 ) Our scoping review, in contrast with previous reviews,(42,93) highlights a shift from using arbitrary pressures to more reliable methods for determining LOP, autoregulated devices, with automatic LOP measurement capability.(94,95) Ensuring optimal LOP is crucial for the efficacy and safety of BFR combined with exercise.(57,95,96) None of the studies included in our review reported adverse events, supporting Bond's assertion of a low risk of thromboembolism associated with BFR.(97) Notably, our study population typically excludes individuals at high risk for thromboembolism. To increase safety, clinicians should thoroughly screen for signs of venous thromboembolism, assess individual risks, and implement appropriate protocols when integrating BFR. LIMITATIONS Our scoping review identified several limitations in the current scientific literature on BFR combined with exercise and ACLR, as summarized in Table 4 . A notable gap exists in studies applying BFR combined with endurance training for ACLR. The considerable heterogeneity in study designs complicates direct comparisons, whereas the limited number of studies affects overall comprehensiveness. Variations in BFR combined with exercise interventions, outcome measures, and exercise parameters significantly influence outcomes. Additionally, diverse measures and non-standarized follow-up further complicate synthesis and long-term effect assessment. The complexity of blinding therapists and subjects may introduce bias, and the lack of sham situations and intention-to-treat analyses further undermines the robustness of the findings. Poor reporting of exercise-related parameters also necessitates caution when interpreting results. Owing to the diversity of outcomes and parameters, conducting a meta-analysis was not feasible, and in some cases, data extraction from articles( 39 – 41 , 43 , 46 ) was not possible. A limitation of our review is the potential exclusion of relevant studies due to the omission of certain databases in the search process. Therefore, further studies are needed to explore long-term effects, adaptations, recovery, and reinjury rates of both PRE- and POST-OP interventions. To draw more definitive conclusions, further research with improved methodologies and patient follow-up is essential. Despite these challenges, the current literature underscores the growing importance of BFR-RT during PRE- and POST-OP phases for ACLR. Table 4 Identified knowledge gaps in literature and recommendations for future studies Identified knowledge gaps from scoping review Implications for future research Lack of comparative studies and limited evidence Lack of comparative studies directly comparing the effects BFR-RT on ACLR interventions to other exercise modalities or control/comparison groups. This limitation hampers our ability to comprehensively understand the advantages and disadvantages of BFR-RT in diverse populations and contexts. Lack of studies with diverse in participant populations The majority of BFR-RT and ACLR studies have primarily involved young and healthy participants without relevant pathologies or diseases beyond the ACL injury and concomitant meniscal procedures. Future research should prioritize addressing specific populations, such as conducting studies on specific sports, targeted age groups, and specific types of surgery interventions. Lack of understanding of the physiological mechanisms Understanding the underlying physiological mechanisms of the BFR-RT effect in ACLR recovery is crucial. Further research is needed to elucidate the specific responses and adaptations that occur with BFR-RT in ACLR rehabilitation. Investigating these mechanisms will provide a deeper understanding of how BFR-RT influences the healing and recovery process in ACL injuries. Lack of research on long-term effects Longitudinal studies on prolonged BFR-RT effects, specifically examining the long-term effects on muscle function, physical and physiological parameters, as well as potential adverse effects, is limited. More research is needed to understand the long-term effects of BFR-RT interventions. Lack of standardized protocols The absence of consensus on standardized BFR-RT protocols and parameters challenges the translation of findings. Establishing evidence-based guidelines for optimal BFR-RT protocols is crucial for enhancing consistency and facilitating effective implementation of BFR-RT. Lack of comparative studies and/or meta-analyses examining the dosage effects of -RT in ACLR: There is a need for comparative studies and/or future meta-analyses to elucidate the dosage effects of BFR-RT. This would help determine the optimal BFR-RT protocols and dosages for different populations and outcomes. Lack of standardized scales for assessing the methodological description of training and occlusion of BFR-RT. Scales are needed to accurately describe and compare key BFR-RT parameters, enhancing research transparency and reproducibility. Lack of studies on the PRE-OP of BFR-RT application in ACLR: There is a lack of studies investigating the effects of PRE-OP BFR-RT application as part of rehabilitation following an ACL injury. Lack of standardized BFR devices There is a need for studies that compare different BFR devices, as currently, no device has been validated their methods for calculating the Limb Occlusion Pressure (LOP). CONCLUSION The evidence examined demonstrates that the use of BFR-RT for ACLR holds significant promise in both PRE and POST-OP phases. In the PRE-OP phase, BFR-RT application significantly increased muscle strength and endurance and parameters linked to angiogenesis and transcriptional responses in comparison with LL-RT. Postoperatively, notable improvements in the BFR-RT group were observed in self-report questionnaires, knee pain, muscle volume, and muscle strength. When BFR-LL was compared with HL-RT, BFR-LL showed similar or greater improvements in functional measurements, muscle hypertrophy, and strength, although it also reported greater muscle pain during training. While home-based exercise interventions were feasible and well tolerated by patients, BFR-LL did not yield significant long-term results in comparison with LL-RT. The findings support the integration of BFR-RT into clinical practice, particularly during the early rehabilitation phases post-ACLR when weight-bearing activities are limited. BFR protocols can be adopted to enhance muscle strength and endurance while minimizing the risks of disuse atrophy. Clinicians should adopt a patient-centered perspective, tailoring BFR interventions to individual needs, ensuring both safety and comfort to maximize recovery benefits. Further research is needed to fully understand the physiological effects of BFR-RT in ACLR rehabilitation, validate existing findings, and establish precise parameters for clinical implementation. Additionally, more studies on BFR-ET are necessary to explore its potential benefits. Standardizing outcomes and methodologies, along with conducting additional randomized controlled trials with larger samples and extended follow-up periods, will enhance the understanding and integration of BFR-RT into clinical practice. Abbreviations ACL, anterior cruciate ligament; ACLR, anterior cruciate ligament reconstruction; BC, body composition; BFR, blood flow restriction; BFR-LL, blood flow restriction light load; BFR-RT, blood flow restriction resistance training; BMD, bone mineral density; BMI, body mass index; BTB, bone-patella tendon-bone autograft; CBFR-HL, concentric blood flow restriction with heavy load; CG, comparison group; CKC, closed kinetic chain; CSA, cross-sectional area; DEXA, dual-energy X-ray absorptiometry; EBFR-HL, eccentric blood flow restriction with heavy load; FI, fatigue indexes; FITT-VP, frequency, intensity, type, time, volume, and progression; FM, functional measurements; HL-RT, high load resistance training; HS, hamstrings tendon; IG, intervention group; IKDC, International Knee Documentation Committee; IL, injured leg; KE, knee extension; KOOS, Knee Injury and Osteoarthritis Outcome Score; LEFS, Lower Extremity Functional Scale; LOP, limb occlusive pressure; M, man; MMHG, millimeters of mercury; MRI, magnetic resonance imaging; MPB, muscle physiology and biomarkers; MVIC, maximum voluntary isometric contraction; N, sample number; NMAR, neuromuscular adaptations and responses; N/S, not specified; OKC, open kinetic chain; POST, posterior; POST-OP, postoperative; PRE-OP, preoperative; QRCT, quasi-randomized controlled trial; QT, quadriceps tendon; RCT, randomized controlled trial; RM, repetition maximum; RPE, rate of perceived exertion; RTA, return to activity; RT, resistance training; SRQ, self-report questionnaires; VAS, visual analog scale; W, woman; y.o, years old. Declarations Ethics approval and consent to participate: Not applicable Consent for publication: Not applicable Availability of data and materials: Data and materials are included in the article. Competing interests: The authors certify that they have no affiliations with or financial involvement in any organization or entity with a direct financial interest in the subject matter or materials discussed in the article. Funding: Not applicable Authors' contributions: Roger Fontanet designed and conducted the study, including the literature review, data analysis, and manuscript drafting. Eduardo Carballeira contributed to the methodological design, provided input on the study framework and statistical analysis, and reviewed the manuscript. Rafel Donat supervised the study, assisted with the methodological tools and techniques, and reviewed the manuscript. All authors approved the final version of the manuscript. 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J Sport Health Sci . 2022;11(2):202-211. doi:10.1016/J.JSHS.2021.01.007 Sieljacks P, Degn R, Hollaender K, Wernbom M, Vissing K. Non-failure blood flow restricted exercise induces similar muscle adaptations and less discomfort than failure protocols. Scand J Med Sci Sports . 2019;29(3):336-347. doi:10.1111/SMS.13346 Husmann F, Mittlmeier T, Bruhn S, Zschorlich V, Behrens M. Impact of Blood Flow Restriction Exercise on Muscle Fatigue Development and Recovery. Med Sci Sports Exerc . 2018;50(3):436-446. doi:10.1249/MSS.0000000000001475 Freitas EDS, Miller RM, Heishman AD, Aniceto RR, Silva JGC, Bemben MG. Perceptual responses to continuous versus intermittent blood flow restriction exercise: A randomized controlled trial. Physiol Behav . 2019;212:112717. doi:10.1016/J.PHYSBEH.2019.112717 Yasuda T, Loenneke J, Ogasawara R, Abe T. Influence of continuous or intermittent blood flow restriction on muscle activation during low-intensity multiple sets of resistance exercise. Acta Physiol Hung . 2013;100(4):419-426. doi:10.1556/APHYSIOL.100.2013.4.6 Caetano D, Oliveira C, Correia C, Barbosa P, Montes A, Carvalho P. Rehabilitation outcomes and parameters of blood flow restriction training in ACL injury: A scoping review. Physical Therapy in Sport . 2021;49:129-137. doi:10.1016/J.PTSP.2021.01.015 McEwen JA, Owens JG, Jeyasurya J. Why is it Crucial to Use Personalized Occlusion Pressures in Blood Flow Restriction (BFR) Rehabilitation? J Med Biol Eng . 2019;39(2):173-177. doi:10.1007/S40846-018-0397-7/FIGURES/3 Jacobs E, Rolnick N, Wezenbeek E, et al. Investigating the autoregulation of applied blood flow restriction training pressures in healthy, physically active adults: an intervention study evaluating acute training responses and safety. Br J Sports Med . 2023:bjsports-2022-106069. doi:10.1136/BJSPORTS-2022-106069 Caetano D, Oliveira C, Correia C, Barbosa P, Montes A, Carvalho P. Rehabilitation outcomes and parameters of blood flow restriction training in ACL injury: A scoping review. Physical Therapy in Sport . 2021;49:129-137. doi:10.1016/J.PTSP.2021.01.015 Bond CW, Hackney KJ, Brown SL, Noonan BC. Blood Flow Restriction Resistance Exercise as a Rehabilitation Modality Following Orthopedic Surgery: A Review of Venous Thromboembolism Risk. https://doi.org/102519/jospt20198375 . 2018;49(1):17-27. doi:10.2519/JOSPT.2019.8375 Tables Tables 2 and 3 are available in the Supplementary Files section. Additional Declarations The authors declare no competing interests. Supplementary Files Table2and3.docx APPENDIX.docx Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6062247","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Systematic Review","associatedPublications":[],"authors":[{"id":417903820,"identity":"2550752d-82c3-4d0e-b34f-986df140c69d","order_by":0,"name":"Roger Fontanet Claret","email":"","orcid":"https://orcid.org/0009-0007-8190-523X","institution":"University of Vic","correspondingAuthor":false,"prefix":"","firstName":"Roger","middleName":"Fontanet","lastName":"Claret","suffix":""},{"id":417904519,"identity":"63f13afb-26c2-41e4-8545-cb7fd2fa99a6","order_by":1,"name":"Rafel Donat Roca","email":"","orcid":"https://orcid.org/0000-0001-6699-6857","institution":"University of Vic","correspondingAuthor":false,"prefix":"","firstName":"Rafel","middleName":"Donat","lastName":"Roca","suffix":""},{"id":417904520,"identity":"2cf294e2-af02-4d99-abad-8c130b062c69","order_by":2,"name":"Eduardo Carballeira","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA00lEQVRIiWNgGAWjYJACZgYGCxl+BubGA2A2kVokeCQbGBtI1GJwgFgt/OyHn30uqJHgMb6RCNRSYZ3YwN7+AK8WyZ4049kzjknwmIG1nElPbOA5Y4BXi8ENBmNmHjaoFsa2w4kNEjn4HWZ/g/0zM88/oMNmgLT8A2qRf47fYQZAxcy8bUDvS4C0NIBsYcDvMIkzOcXMM/skeCTOPGw4kHAs3biNJwe/Fv7245uZC77ZyPG3Jx988KHGWraf/Th+h6GCBCBmI0H9KBgFo2AUjAIcAABdOEMbEusThQAAAABJRU5ErkJggg==","orcid":"https://orcid.org/0000-0001-5305-9581","institution":"Universidad de La Laguna","correspondingAuthor":true,"prefix":"","firstName":"Eduardo","middleName":"","lastName":"Carballeira","suffix":""}],"badges":[],"createdAt":"2025-02-19 08:48:00","currentVersionCode":1,"declarations":{"humanSubjects":false,"vertebrateSubjects":false,"conflictsOfInterestStatement":false,"humanSubjectEthicalGuidelines":false,"humanSubjectConsent":false,"humanSubjectClinicalTrial":false,"humanSubjectCaseReport":false,"vertebrateSubjectEthicalGuidelines":false},"doi":"10.21203/rs.3.rs-6062247/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6062247/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":76880551,"identity":"ff315637-23f3-45da-81af-3eacf6ba495e","added_by":"auto","created_at":"2025-02-21 17:01:19","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":257526,"visible":true,"origin":"","legend":"\u003cp\u003ePRISMA flow chart with information on the specifics of the search process.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-6062247/v1/3f1599c31e022cecb29c7973.png"},{"id":76880544,"identity":"60f229d7-9993-4883-bfbf-b0bed6677454","added_by":"auto","created_at":"2025-02-21 17:01:19","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1139639,"visible":true,"origin":"","legend":"\u003cp\u003eA: PEDro scale for risk of bias assessment by study. B. PEDro scale for risk of bias assessment by item (%).\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-6062247/v1/8386095f46014f250ed8f418.png"},{"id":76881851,"identity":"354f6c9c-49d4-48fd-95e9-274b9be0cf7a","added_by":"auto","created_at":"2025-02-21 17:17:28","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2353711,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6062247/v1/1a00b2c2-bb3f-423d-8084-8aeba21cc83e.pdf"},{"id":76880555,"identity":"a27fbb78-47a5-4544-af76-c92de813b862","added_by":"auto","created_at":"2025-02-21 17:01:19","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":1211504,"visible":true,"origin":"","legend":"","description":"","filename":"Table2and3.docx","url":"https://assets-eu.researchsquare.com/files/rs-6062247/v1/b06f702944c4e08a878c68bb.docx"},{"id":76881514,"identity":"e5b48464-72e9-4c0d-a941-866c77a9f055","added_by":"auto","created_at":"2025-02-21 17:09:19","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":1190444,"visible":true,"origin":"","legend":"","description":"","filename":"APPENDIX.docx","url":"https://assets-eu.researchsquare.com/files/rs-6062247/v1/3b6ab6ddac4796d689c5b334.docx"}],"financialInterests":"The authors declare no competing interests.","formattedTitle":"\u003cp\u003e\u003cstrong\u003eBlood Flow Restriction Training Prior to and After Anterior Cruciate Ligament Reconstruction: A Scoping review\u003c/strong\u003e\u003c/p\u003e","fulltext":[{"header":"INTRODUCTION","content":"\u003cp\u003eThe occurrence of anterior cruciate ligament (ACL) injuries has tended to increase, notably affecting adolescent athletes(\u003cspan additionalcitationids=\"CR2 CR3\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e) and the general population.(\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e) The annual incidence is estimated to be approximately 0.01\u0026ndash;0.05% in the general population, 0.15 to 7.32% in professional athletes, and 0.002 to 1.62% in amateur athletes.(\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e) Over the past few decades, there has been a significant increase in ACL injuries among young athletes, with increases ranging from 44\u0026ndash;143%.(\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e) ACL injury directly impacts the quality of life of injured individuals and has a high socioeconomic impact in both the short and long term.(\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eIn the early stages following ACL reconstruction (ACLR), prescribed immobilization, restricted weight bearing, intraoperative tourniquet, and the inability to perform heavy load resistance training (HL-RT) and/or high-intensity endurance exercises collectively contribute to muscular atrophy and weakness in the lower extremities.(\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e) This particularly affects the quadriceps, which is a clinical manifestation and primary risk factor for the development of knee osteoarthritis,(\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e) and leads to deconditioning in the injured individual, thereby delaying their return to activity. Muscular strength and hypertrophy are primarily induced through heightened firing rates and enhanced recruitment of motor neurons, thereby resulting in increased mechanical tension within the engaged myofibers.(\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e) Optimal development of maximal strength and power is achieved by employing heavy loads (\u0026ge;\u0026thinsp;85% of one repetition maximum, 1RM) and moderate loads (40% \u0026minus;\u0026thinsp;70% 1RM), respectively.(\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e) However, traditional muscle-strengthening training involving near-maximal loads or engaging in contractions at maximum voluntary velocity is not recommended during the initial stages following ACLR.(\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e) Consequently, there has been a growing interest in blood flow restriction (BFR) applied to proximal limbs during exercise as a potentially effective method for inducing neuromuscular, vascular and metabolic adaptations with lower intensities than typically needed.(\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e) This technique has demonstrated the ability to enhance skeletal muscle fiber growth and neural function,(\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e) as well as long-term changes in mitochondrial and microvascular adaptations.(\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e) Such adaptations could offer benefits in both the preoperative (PRE-OP) and postoperative (POST-OP) phases of ACLR while also providing a peripheral stimulus to improve cardiovascular fitness,(\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e) which is often diminished after ACLR rehabilitation compared with preinjury values. (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eBlood flow restriction resistance training (BFR-RT) and BFR endurance training (BFR-ET) have emerged as promising alternative to traditional HL-RT or high-intensity training; these methods yield comparable neuromuscular adaptations(\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e) and offer benefits such as alleviating knee pain, reducing swelling, and improving functionality.(\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e) Furthermore, BFR-RT has been implemented in PRE-OP phases to confer protective effects against ischemia-induced injury and bolster muscle strength and endurance for faster rehabilitation.(\u003cspan additionalcitationids=\"CR25\" citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e) On the other hand, BFR-RT applied during the POST-OP phases enhances skeletal muscle hypertrophy and functional measurements to a similar extent as HL-RT.(\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e) Furthermore, BFR-ET during the POST-OP phase resulted in reduced moments around the knee joint compared with the no-BFR condition, suggesting that BFR-ET is a safe option to utilize following ACLR.(\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eTherefore, we conducted a scoping review to comprehensively explore existing research, establish terminology, identify potential pathways for targeted design of future interventional studies, and pave the way for the application of BFR in clinical practice.(\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e) The current review aimed to address the following research questions: 1) What are the effects of BFR-RT or BFR-ET compared with other training protocols without BFR, both PRE-OP and POST-OP, in patients undergoing ACLR; 2) What are the commonly used training and BFR parameters during BFR-RT and BFR-ET protocols, both PRE-OP and POST-OP, in patients undergoing ACLR.\u003c/p\u003e"},{"header":"METHODS","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eProtocol and Registration\u003c/h2\u003e \u003cp\u003eWe conducted a scoping review to explore the effects of BFR training on ACL injury and identify areas where further research is needed(\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e). We aimed to understand the responses and adaptations induced by BFR in the neuromuscular, peripheral vascular, and peripheral metabolic systems. This review followed the recommendations from the PRISMA applied to exercise, rehabilitation, sports medicine, and sports science.(\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e) We registered the present review in Open Science Framework (April 1 2024; \u003cb\u003eDOI\u003c/b\u003e: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.17605/OSF\u003c/span\u003e\u003cspan address=\"10.17605/OSF\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e. IO/76243; \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://osf.io/76243/?view_only=d944754ee6404bc19fa4d7addc950d54\u003c/span\u003e\u003cspan address=\"https://osf.io/76243/?view_only=d944754ee6404bc19fa4d7addc950d54\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eEligibility criteria\u003c/h3\u003e\n\u003cp\u003eThe PICOS approach guided the selection of eligible sources, with inclusion criteria outlined in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, which required articles to be peer-reviewed original research, available in full-text format, no language restrictions were applied.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eInclusion and exclusion criteria based on the PICOS strategy\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eInclusion criteria\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eExclusion criteria\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePopulation\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eHuman healthy patients affected by a primary ACL injury with or without concomitant meniscal procedures and surgically intervened with patellar, quadriceps, or hamstring tendon autograft were included.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePrevious ACL injury, additional knee impairments, or multiple reconstructive procedures.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIntervention\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eInterventions that combined BFR and resistance exercises or endurance exercises applied during PRE- and/or POST-OP phases. The duration of the intervention should be at least one week for both PRE- and POST-OP.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eAnalyses were not conducted independently for interventions combining BFR with techniques such as electrostimulation or other modalities, or the duration of the interventions were lower than required in the inclusion criteria.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eComparator\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eComparison group performing resistance exercises or endurance exercises with or without BFR or a placebo (i.e., sham BFR).\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eThere is no control/comparison group. Articles that do not contain a comparative analysis with control/comparison groups without BFR during exercise interventions, or a placebo (i.e., simulated BFR).\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOutcomes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eValidated assessment analyzing muscular structural changes, muscle strength, neuromuscular adaptations and responses, functional changes, self-report questionnaires, pain, peripheral vascular and local metabolic parameters.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNo reported validated tests providing quantitative values.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eStudy design\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRandomized controlled trials or quasi-randomized controlled trials with pre-post measurements of one or more outcomes, comparing BFR to a control or comparison group.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eOpinion articles, editorials, systematic reviews, case-control studies, case series studies, conference abstracts, in-progress articles, cohort articles, cross-sectional articles, and studies with results obtained without an initial evaluation.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e \u003cp\u003eACL, anterior cruciate ligament; BFR, blood flow restriction; PRE-OP, preoperative; POST-OP, postoperative; QRCT, Quasi-randomized controlled trial; RCT, Randomized controlled trial.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e\n\u003ch3\u003eStrategy of Search and Databases\u003c/h3\u003e\n\u003cp\u003eSystematic literature searches were carried out in three phases. In the first phase, SWIFT-reviewer(\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e) was utilized for the initial exploratory search. Specific keywords such as BFR and ACL were employed to delve into, categorize, and determine the terms to utilize. In the second phase, primary searches were conducted on various databases, including Web of Science (WoS), PEDro, Scopus, PUBMED (MEDLINE), SportDiscus, and Cochrane Library databases, from inception until 22-01-2025. The search formula was adapted according to the specifics of the respective database and contained a combination of terms related to BFR and ACL injury. The search fields, filters, and results from the electronic database can be found in supplemental appendix A. In the third phase, we introduced the eligible articles from the second phase into the Citation Chaser.(\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e) This web platform was used to find potential articles in forward (articles that cited the eligible articles) and backward (references within the eligible articles) citation chasing in the literature. Additionally, a search in the grey literature was conducted using platforms such as OpenGrey, OAlster, and Google Scholar to ensure comprehensive coverage of relevant studies and reports not found in traditional academic databases. The authors were also contacted when supplementary material for specific articles was unavailable.\u003c/p\u003e\n\u003ch3\u003eSelection of Sources of Evidence and Data Extraction\u003c/h3\u003e\n\u003cp\u003eThe selection and screening process was conducted via Rayyan.(\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e) Two independent reviewers (XXX and XXX) screened the titles and abstracts of the articles via a blinded platform(\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e) to assess their eligibility according to inclusion and exclusion criteria, both in the first and second phases of the search. An experienced supervisor (XXX) was blinded to resolve conflicts in the screening process. The articles that passed the title and abstract screening were entered into the Citation Chaser platform(\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e) for exhaustive tracking of backward and forward citations. Finally, the screening process was repeated for full-text review. The data extraction from the selected studies was conducted by two reviewers (XXX and XXX), and conflicts were discussed by two supervisors (XXX and XXX).\u003c/p\u003e\n\u003ch3\u003eRisk of Bias, Quality of Evidence, and Quality of Exercise Reporting\u003c/h3\u003e\n\u003cp\u003eThe methodological quality of the RCTs and QRCTs was evaluated via the Physiotherapy Evidence Database (PEDro)(\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e) bias detection tool, which evaluates eleven specific criteria.\u003c/p\u003e \u003cp\u003eThe Consensus on Exercise Reporting Template (CERT)(37) was used to evaluate whether the reviewed articles provided a structured framework and effectively documented and reported exercise outcomes and parameters. The results are presented in supplemental appendix C. Two evaluators conducted all assessments, and a third reviewer resolved any possible conflicts.\u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eData Items and Synthesis of Results\u003c/h2\u003e \u003cp\u003eThe study variables were categorized into six sections: body composition (including muscle volume, thickness, cross-sectional area and changes in site-specific bone mass, bone mineral density, whole limb lean mass); neuromuscular adaptations and responses (including maximum voluntary isometric contraction, isokinetic strength, activation of vastus medialis, central activation ratio of knee extensors, and fatigue indexes); functional measurements (including all tests and values related to functionality); self-report questionnaires (including patient-reported scales and questionnaires); muscle physiology and biomarkers(including muscle biopsy analysis and blood sample analysis); and return to activity time. The results were systematically categorized and summarized into key thematic areas, and the evidence was presented in a narrative format and complemented by tables.\u003c/p\u003e \u003c/div\u003e"},{"header":"RESULTS","content":"\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\n \u003ch2\u003eStudy characteristics and strength of recommendations\u003c/h2\u003e\n \u003cp\u003eLiterature searches conducted across six different databases yielded 385 articles. After removing 74 duplicate articles and applying selection criteria to 311 articles based on title and abstract, 268 articles were excluded. A comprehensive assessment of the full texts of 33 articles was subsequently conducted, which led to the exclusion of eighteen articles: seven were excluded because of the wrong article type, another seven were omitted due to inaccuracies in outcome measurement and registration, and the remaining four were discarded because of an incorrect study design. In addition to the main search, a backward and forward citation chase identified 1,594 articles, and a grey literature search yielded 1,630 articles. Fifteen articles were assessed for eligibility, but all were duplicates of those found in the main search. Finally, a total of 15 studies were included in the present review. Twelve were randomized controlled trials,(\u003cspan class=\"CitationRef\"\u003e38\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e46\u003c/span\u003e) and the remaining three were quasi-randomized controlled trials.(\u003cspan class=\"CitationRef\"\u003e47\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e49\u003c/span\u003e) The details of the charting process, with the specific reasons for exclusion, can be seen in Fig.\u0026nbsp;1.\u003c/p\u003e\n \u003cp\u003eThe overall number of articles selected demonstrated a low risk of bias according to the PEDro(\u003cspan class=\"CitationRef\"\u003e36\u003c/span\u003e) scale, as shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e, with a median score of 6,87 out of 10 for all included RCTs and QRCTs. The lowest score recorded was 6, indicating an acceptable level of quality, whereas the highest score achieved was 9, reflecting excellent quality. Most of the selected studies exhibited bias regarding blinding of all subjects (80%) and all therapists (86,67%).\u003c/p\u003e\n \u003cp\u003eThe PRE-OP articles met the specified criteria of the CERT(37) scale in 51,6% of the cases, whereas the POST-OP studies met it in 60,8% of the cases (supplemental appendix C).\u003c/p\u003e\n \u003cp\u003eThe final analysis included 417 patients who underwent ACLR (285 males and 132 females). All studies utilized BFR-RT as the experimental intervention, with one applying a cross BFR education protocol to the uninjured leg(\u003cspan class=\"CitationRef\"\u003e50\u003c/span\u003e), and none employing BFR-ET. Five studies used BFR-RT during the PRE-OP phase(\u003cspan class=\"CitationRef\"\u003e46\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e47\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e49\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e51\u003c/span\u003e) nine were conducted POST-OP phase (\u003cspan class=\"CitationRef\"\u003e40\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e45\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e50\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e52\u003c/span\u003e) and one study was performed in both the PRE- and POST-OP,(\u003cspan class=\"CitationRef\"\u003e53\u003c/span\u003e) which was discussed in the POST-OP results due to its longer follow-up and more extensive control during that phase. The general characteristics of included studies (time of intervention, author, study design, autograft type, intervention time, population, sample characteristics, groups, and studied variables) are shown in Table 2.\u003c/p\u003e\n \u003cp\u003eThe CERT scale(37) was employed to ensure comprehensive reporting of exercise parameters (supplemental appendix C), while the distribution of studies based on the FITT-VP parameters,(\u003cspan class=\"CitationRef\"\u003e54\u003c/span\u003e) describing exercise variables such as frequency, intensity, time, type, volume, and progression, is detailed in supplemental appendix D. Various training protocols were employed, with training loads ranging from body weight to 70% of 1 repetition maximum and training intensity was predominantly determined by calculating the percentage of 1 repetition maximum. (\u003cspan class=\"CitationRef\"\u003e40\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e43\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e47\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e49\u003c/span\u003e)\u003c/p\u003e\n \u003cp\u003eIntermittent(\u003cspan class=\"CitationRef\"\u003e43\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e44\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e46\u003c/span\u003e) and continuous(\u003cspan class=\"CitationRef\"\u003e38\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e40\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e42\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e45\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e50\u003c/span\u003e) rest periods were utilized, with various tools employed for calculating limb occlusion pressure (LOP). No adverse events were reported during interventions(\u003cspan class=\"CitationRef\"\u003e38\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e40\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e42\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e45\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e46\u003c/span\u003e). Specific training parameters and cuff details for individual studies are outlined in Table 3.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\n \u003ch2\u003eOutcome Measures\u003c/h2\u003e\n \u003cdiv id=\"Sec12\" class=\"Section3\"\u003e\n \u003ch2\u003eBody composition\u003c/h2\u003e\n \u003cp\u003eThe PRE-OP interventions demonstrated improvements(\u003cspan class=\"CitationRef\"\u003e47\u003c/span\u003e) or comparable(\u003cspan class=\"CitationRef\"\u003e38\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e46\u003c/span\u003e) results in quadriceps cross-sectional area (CSA) between BFR-RT groups and comparison groups.\u003c/p\u003e\n \u003cp\u003eIn POST-OP studies, BFR-LL demonstrated comparable CSA effects to HL-RT at 70% 1RM,(\u003cspan class=\"CitationRef\"\u003e41\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e45\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e53\u003c/span\u003e) yet combining BFR with HL (BFR-HL) yielded no additional benefits.(\u003cspan class=\"CitationRef\"\u003e43\u003c/span\u003e) While combining BFR-RT with home-based intervention with body-weighted isometric protocols appeared ineffective.(\u003cspan class=\"CitationRef\"\u003e44\u003c/span\u003e) Jack et al.(\u003cspan class=\"CitationRef\"\u003e42\u003c/span\u003e) observed a protective effect of BFR-LL against POST-OP bone loss, in contrast with the significant declines in lean mass observed in the comparison group.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\n \u003ch2\u003eNeuromuscular adaptations and responses\u003c/h2\u003e\n \u003cp\u003ePRE-OP interventions significantly improved knee extensor peak torque(\u003cspan class=\"CitationRef\"\u003e38\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e47\u003c/span\u003e) or yielded similar results(\u003cspan class=\"CitationRef\"\u003e46\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e49\u003c/span\u003e)(\u003cspan class=\"CitationRef\"\u003e38\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e46\u003c/span\u003e).(\u003cspan class=\"CitationRef\"\u003e47\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e49\u003c/span\u003e) A PRE-OP research team made significant progress in their studies,(\u003cspan class=\"CitationRef\"\u003e47\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e49\u003c/span\u003e) consistently achieving favorable outcomes within the BFR-LL group and effectively preventing the deterioration of maximal muscle strength and knee extensor endurance.\u003c/p\u003e\n \u003cp\u003eHughes et al.(\u003cspan class=\"CitationRef\"\u003e41\u003c/span\u003e) POST-OP study compared BFR-LL at 30% and HL-RT at 70%. At 8 weeks, both groups showed similar increases in scaled 10RM strength and similar decreases in knee extension peak torque. However, HL-RT group presented significantly greater decreases in knee flexion peak torque at all speeds compared to BFR-LL group. This was accompanied by a strong effect size, suggesting a more detrimental effect for HL-RT. Vieira et al.(\u003cspan class=\"CitationRef\"\u003e45\u003c/span\u003e) utilized similar groups and reported that compared with HL-RT, BFR-LL resulted in significantly greater improvements in muscle strength within a shorter rehabilitation period while Curran et al.(\u003cspan class=\"CitationRef\"\u003e43\u003c/span\u003e) demonstrated that HL-RT alone resulted in significant improvements in quadriceps muscle strength, without any additional benefit from incorporating BFR to HL-RT. Additionally, Erickson et al,(\u003cspan class=\"CitationRef\"\u003e53\u003c/span\u003e) showed that BFR-LL was equally effective as sham BFR group combined with HL-RT in their PRE- and POST-OP study. Ultimately, Sevinc(\u003cspan class=\"CitationRef\"\u003e50\u003c/span\u003e) found a significant main effect of time on quadriceps strength in both the involved (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001) and uninjured limbs, with no additional gains from adding BFR to cross-education in post-ACLR patients.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\n \u003ch2\u003eSelf-report questionnaires\u003c/h2\u003e\n \u003cp\u003eSelf-report questionnaires were assessed in seven studies to evaluate knee pain, muscle pain, rate of perceived exertion, knee function, knee symptomatology, and self-perceived depression.(\u003cspan class=\"CitationRef\"\u003e38\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e41\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e43\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e45\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e46\u003c/span\u003e) Home-based PRE-OP interventions yielded similar(\u003cspan class=\"CitationRef\"\u003e46\u003c/span\u003e) or improved(\u003cspan class=\"CitationRef\"\u003e38\u003c/span\u003e) outcomes between BFR-LL and LL-RT. However, in POST-OP interventions, BFR-RT consistently improved knee joint pain and self-reported outcomes in studies comparing BFR-LL vs HL-RT,(\u003cspan class=\"CitationRef\"\u003e40\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e41\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e45\u003c/span\u003e) except for muscle pain immediately following each set of exercise,(\u003cspan class=\"CitationRef\"\u003e40\u003c/span\u003e) where the BFR-LL group had worse values than the HL-RT group. Additionally, the study of Khalil et al.(\u003cspan class=\"CitationRef\"\u003e39\u003c/span\u003e) compared BFR-LL vs LL-RT and another study comparing BFR-HL (70% 1 RM) vs HL-RT(\u003cspan class=\"CitationRef\"\u003e43\u003c/span\u003e) did not yield significant improvements.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\n \u003ch2\u003eFunctional Measurements\u003c/h2\u003e\n \u003cp\u003eThree PRE-OP studies investigated functional measurements but did not find significant improvements in knee ROM(\u003cspan class=\"CitationRef\"\u003e38\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e46\u003c/span\u003e) or Y-balance tests(\u003cspan class=\"CitationRef\"\u003e49\u003c/span\u003e). However, in contrast, POST-OP interventions demonstrated significant results. Hughes et al(\u003cspan class=\"CitationRef\"\u003e41\u003c/span\u003e) reported significant improvements in Y-balance on the injured leg across all directions (anterior, posteromedial, and posterolateral), with the BFR-LL group exhibiting a strong effect size compared with the HL-RT group. Additionally, in the study by Jack et al.,(\u003cspan class=\"CitationRef\"\u003e42\u003c/span\u003e) significant improvement in Y balance was observed only in the BFR-LL group between 8 and 12 weeks compared with the LL-RT group.\u003c/p\u003e\n \u003cp\u003eAdditionally, Hughes et al.(\u003cspan class=\"CitationRef\"\u003e41\u003c/span\u003e) demonstrated significant improvements in mid-patellar knee joint circumference and knee range of motion (ROM), with no observed changes in knee laxity in the BFR-LL group.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\n \u003ch2\u003eMuscle Physiology and Biomarkers\u003c/h2\u003e\n \u003cp\u003eIn the PRE-OP study by Žargi et al.(\u003cspan class=\"CitationRef\"\u003e49\u003c/span\u003e) significant improvements in muscle blood flow were observed at week 4 POST-OP in the BFR-LL group (\u0026uarr;52%) compared with the SHAM-BFR group (\u0026darr;37%), with a notable interaction detected between time and group factors in muscle blood flow. Additionally, Kacin et al.(\u003cspan class=\"CitationRef\"\u003e47\u003c/span\u003e) conducted a biopsy analysis, emphasizing the role of hypoxia-inducible factor 1-alpha (HIF-1\u0026alpha;) in cellular adaptation to hypoxia. These authors reported higher mRNA levels of VEGF-A, which is crucial for angiogenesis regulation, in the BFR-LL group than in the SHAM-BFR group.\u003c/p\u003e\n \u003cp\u003eRegarding the POST-OP phase, one study(\u003cspan class=\"CitationRef\"\u003e52\u003c/span\u003e) examined key biomarkers related to muscle atrophy following ACLR through blood samples. The results showed significant reductions in serum Atrogin-1 (\u0026darr;-12.53%) and serum MuRF1 (\u0026darr;-15.47%) from week 0 to week 12 in the BFR-RT group compared to the RT group, with a significant group x time interaction for Atrogin-1 and a significant time effect for both biomarkers (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e\n \u003ch2\u003eReturn to activity time\u003c/h2\u003e\n \u003cp\u003eJack et al.(\u003cspan class=\"CitationRef\"\u003e42\u003c/span\u003e) demonstrated a significant reduction in the time to return to sports by 1.4 months, accompanied by a strong effect size, in a 12-week rehabilitation protocol when BFR-LL was compared with LL-RT. Curran et al.(\u003cspan class=\"CitationRef\"\u003e43\u003c/span\u003e) found no significant differences between BFR-HL and HL-RT.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec18\" class=\"Section2\"\u003e\n \u003ch2\u003eExercise Parameters and Reporting Standards\u003c/h2\u003e\n \u003cp\u003eThe CERT scale(37) was used to evaluate the practical implementation and completeness of exercise reporting across the included studies. In our analysis, adherence to the CERT criteria was 51.6% for PRE-OP interventions and 60.8% for POST-OP interventions. Notably, compared with PRE-OP studies, POST-OP studies achieved equal or better results for 13 of the 19 evaluable criteria. Both PRE-OP and POST-OP studies presented low scores in detailing how adherence to exercise is measured and reported (PRE-OP: 0% vs. POST-OP: 42.9%). In contrast, both types of articles provided a detailed description of each exercise to enable replication (PRE-OP: 100% vs. POST-OP: 88.9%). PRE-OP studies accounted for the detailed description of any home program component in 100% of cases, whereas POST-OP studies did so in 55.6% of cases. Finally, 77.8% of POST-OP studies explained how exercises are tailored to the individual, whereas none of the PRE-OP studies reported this. One article that examined both the PRE- and POST-OP phases achieved favorable results in 13 of the 19 criteria. To prevent influencing the outcomes, the study was analyzed separately for each phase.\u003c/p\u003e\n \u003cp\u003eThe reporting of exercise parameters on FITT-VP(\u003cspan class=\"CitationRef\"\u003e54\u003c/span\u003e) framework revealed variability between studies in both phases (supplemental appendix D). PRE-OP studies included short-duration interventions, averaging 1.91 weeks with 5\u0026ndash;10 sessions. In contrast, POST-OP studies utilized longer protocols, all studies with 16 or more sessions, with an average intervention duration of 9 weeks. Additionally, the study that examined both PRE- and POST-OP ACLR phases had a duration of 24 weeks, the longest among all those analyzed. A total of 9 studies from the review utilized personalized exercise protocols. (PRE-OP: 2/5 vs POST-OP: 6/9 vs PRE and POST-OP: 1/1), whereas the remaining studies focused predominantly on specific exercises (PRE-OP: 3/5 for leg extension vs POST-OP: 3/9 for leg press). Regarding repetitions, adherence to the \u0026ldquo;30-15-15-15\u0026rdquo; protocol was noted in 40% of PRE-OP studies compared with 55.5% of POST-OP studies. Additionally, the remaining PRE-OP studies aimed for repetitions to failure, whereas the POST-OP studies that did not follow the \u0026ldquo;30-15-15-15\u0026rdquo; protocol adhered to different repetition patterns, similar to the study that examined both phases and followed its rehabilitation plan. Among the studies reviewed, 66.7% determined the optimal exercise load by one repetition maximum. Training loads for the BFR-RT group ranged from body weight to 30% of 1RM, exceptuating two studies that employed 70% of 1RM. Progression of training stimulus was reported in 2/5 of PRE-OP interventions compared with 8/9 of POST-OP studies and PRE- and POST-OP study 1/1.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"DISCUSSION","content":"\u003cp\u003eIn this scoping review examining the application of BFR-RT before and after ACLR, no study reported that BFR-RT was less effective than the comparison group in any outcome measure, except for one specific study where knee pain during training sessions was greater in the BFR-LL group compared to the HL-RT group. Specifically, 2/5 of PRE-OP studies showed superior outcomes in BFR-RT interventions compared to groups trained with the same or different loads. In POST-OP interventions, 5/9 studies showed superior results for BFR-RT, with the remaining studies finding comparable outcomes between the BFR-RT and comparison groups. None of the studies included BFR-ET, highlighting the need for future research on its effectiveness in ACLR rehabilitation.\u003c/p\u003e \u003cp\u003eBased on the evidence reviewed in PRE and POST-OP phases of ACLR, BFR-RT shows promise as a useful interim step.(\u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e55\u003c/span\u003e) The results of our review regarding body composition, neuromuscular adaptations, muscle physiology and biomarkers, and self-report questionnaires are consistent with those reported in other systematic reviews studying the effects of BFR on ACLR.(\u003cspan additionalcitationids=\"CR57\" citationid=\"CR55\" class=\"CitationRef\"\u003e56\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e58\u003c/span\u003e). Furthermore, we emphasized rigorous methodological evaluation via the PEDro scale.(\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e) Additionally, we employed the CERT scale(37) to assess the quality of reporting exercise parameters. These tools are crucial for extracting reliable information related to exercise parameters and methodology, ensuring that study results are applicable in practical settings. On the other hand, previous reviews have incorporated non-randomized trials and studies with a high risk of bias(\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e59\u003c/span\u003e, \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e60\u003c/span\u003e), which can affect the reliability of the findings. To avoid such biases, we included only RCTs and QRCTs in our review. Our review stands out from previous reviews because of its emphasis on precise article selection criteria, the inclusion of high-quality trials, and the meticulous extraction of information concerning exercise parameters and BFR methodology. This is the first systematic review that specifically evaluated the use of BFR combined with exercise during the PRE-OP and POST-OP in ACLR patients.\u003c/p\u003e \u003cp\u003ePRE-OP interventions were specifically designed to explore the effects of BFR-RT on muscle preservation, strength maintenance, and overall PRE-OP outcomes. Factors such as immobilization, restricted weight bearing, intraoperative tourniquet and nerve block administration during ACLR surgery may contribute to quadriceps weakness.(\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e) This weakness can impact functionality, (\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e61\u003c/span\u003e, \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e62\u003c/span\u003e) quality of life,(\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e) and joint health over time.(\u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e63\u003c/span\u003e) In other reviews, exercise-based prehabilitation has been shown to be favorable for ACLR,(\u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e64\u003c/span\u003e, \u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e65\u003c/span\u003e) whereas adding BFR to prehabilitation appears promising.(\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e) However, Žargi et al.(\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e49\u003c/span\u003e) The initial study implemented BFR-LL with knee extension exercises for 10 days PRE-OP but reported no significant POST-OP effects compared with LL-RT in terms of maximum voluntary isometric contraction and CSA of knee extensors. Other studies highlighted that quadriceps endurance, rather than maximal strength and CSA, emerged as the most significant predictor of quadriceps atrophy following ACLR.(\u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e66\u003c/span\u003e, \u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e67\u003c/span\u003e) Following the PRE-OP protocol established in the study by Zargi et al. (\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e48\u003c/span\u003e)\u003csup\u003e,\u003c/sup\u003e two new studies(\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e47\u003c/span\u003e, \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e49\u003c/span\u003e) selected different outcomes while maintaining the original intervention protocol. A statistically significant group interaction was detected at week 4 POST-OP, with near-infrared spectroscopy and muscle surface electromyography activation.(\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e48\u003c/span\u003e) The second PRE-OP study highlighted statistically significant improvements in muscle fatigue index.(\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e47\u003c/span\u003e) At 3 weeks POST-OP, the BFR-LL group presented a 60% decrease in peak torque at 60\u0026deg;/s, whereas the LL-RT group presented a 21% decrease. The previous results confirm findings in other systematic reviews,(\u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e68\u003c/span\u003e) were improvements related to muscle endurance and blood flow muscle parameters may prevent ischemia‒reperfusion damage and protect against muscle protein oxidation,(\u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e68\u003c/span\u003e, \u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e69\u003c/span\u003e) and consequently, these improvements may serve as a safeguard against the threat of POST-OP quadriceps atrophy.\u003csup\u003e26\u003c/sup\u003e Moreover, the PRE-OP study of Kacin et al.(\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e47\u003c/span\u003e) conducted muscle biopsies in ACLR patients and obtained a significant impact of BFR-RT on vascular endothelial growth factor-A (VEGF-A) and mRNA levels, which are crucial for angiogenesis.(\u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e68\u003c/span\u003e) These results align with trends from other reviews based on the general population.(\u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e68\u003c/span\u003e, \u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e69\u003c/span\u003e) Identifying effective strategies to increase muscle endurance could optimize both PRE and POST-OP results.\u003c/p\u003e \u003cp\u003ePOST-OP interventions using BFR-RT are typically implemented in the early phases after ACLR. These interventions aim to investigate the impact of BFR-RT on muscle recovery, strength restoration, and overall POST-OP rehabilitation in individuals who have undergone ACLR. Specifically, improvements in muscle volume, a key aspect of body composition, were observed and align with findings from other systematic reviews, highlighting the potential of BFR-RT in enhancing muscle recovery and rehabilitation outcomes.(\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e) BFR-LL has been demonstrated to be superior to LL-RT(\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e42\u003c/span\u003e) and comparable to HL-RT(\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e41\u003c/span\u003e, \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e45\u003c/span\u003e) in enhancing muscle volume. Moreover, BFR-HL versus HL-RT yielded similar results;(\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e43\u003c/span\u003e) notably, BFR-HL may deviate from the fundamental physiological principles of BFR-RT, as it involves HL-RT rather than the LL approach typically used in BFR-RT. Additionally, a POST-OP study(\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e52\u003c/span\u003e) analyzed two key biomarkers of muscle atrophy, Atrogin-1 and MuRF1, which are typically elevated in response to disuse. The study found significant reductions in serum Atrogin-1 (\u0026darr;12.53%) and MuRF1 (\u0026darr;15.47%) levels in the BFR-RT group compared to RT, suggesting that BFR may help mitigate muscle protein degradation and prevent atrophy.\u003c/p\u003e \u003cp\u003eParameters related to bone mineral density were examined in the study by Jack et al.(\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e42\u003c/span\u003e) These significant findings align with the meta-analysis by Wang et al.(\u003cspan citationid=\"CR69\" class=\"CitationRef\"\u003e70\u003c/span\u003e) highlighting that BFR-LL training results in greater improvements in bone health than does LL-RT.(\u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e71\u003c/span\u003e) Better bone mineralization may enhance graft integration in ACLR procedures and help prevent conditions such as osteopenia and osteoporosis in specific patients, making this a relevant line of investigation for future research.\u003c/p\u003e \u003cp\u003eA previous meta-analysis(\u003cspan citationid=\"CR71\" class=\"CitationRef\"\u003e72\u003c/span\u003e) focusing on non-injured populations demonstrated that, compared with BFR-LL, HL-RT leads to greater muscle strength gains. However, our review revealed that compared with HL-RT, BFR-LL or BFR-HL interventions produce similar or superior muscle strength\u003csup\u003e42,44,46\u003c/sup\u003e in ACLR patients. (\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e41\u003c/span\u003e, \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e43\u003c/span\u003e, \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e45\u003c/span\u003e) Additionally, a study combining BFR with isokinetic training and cross-education on the uninjured leg found no additional benefits from adding BFR, as both groups achieved similar results.(\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e50\u003c/span\u003e) Comparing BFR-RT to approaches such as BFR-HL or BFR with isokinetic training may have deviated from the fundamental physiological principles of BFR-RT. Moreover, some of these studies concluded that BFR-LL was ineffective simply because it produced similar outcomes to HL-RT, overlooking the fact that achieving comparable results with significantly lower loads is, in itself, a meaningful finding. This misinterpretation may stem from methodological choices, particularly the use of HL-RT 'sham groups' and the selection of comparators, which could have influenced the perceived effectiveness of BFR. During the early to middle stages POST-OP ACLR, BFR-RT has emerged as an effective strategy, particularly when HL-RT may cause pain or when limited mobility or high-load intolerance is present.\u003c/p\u003e \u003cp\u003eKnee pain is a key outcome of ACLR and BFR-RT research. BFR-LL has been shown to facilitate a more rapid reduction in knee pain than HL-RT does, which is correlated with improved functionality and quality of life.(\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e40\u003c/span\u003e, \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e41\u003c/span\u003e, \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e45\u003c/span\u003e) The physiological mechanisms behind BFR-RT induced pain reduction are not fully understood, but several theories have been proposed. These include activation of the opioid and endocannabinoid systems, increased activation of the descending inhibitory pathway, early preferential recruitment of high-threshold motor units (Type II), and conditioned pain modulation, where pressure and discomfort during BFR-RT may act as conditioning stimuli.(\u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e71\u003c/span\u003e, \u003cspan citationid=\"CR72\" class=\"CitationRef\"\u003e73\u003c/span\u003e, \u003cspan citationid=\"CR73\" class=\"CitationRef\"\u003e74\u003c/span\u003e) However, further research is needed to fully understand and validate these mechanisms to establish viable pain management protocols.\u003c/p\u003e \u003cp\u003eIn our review, home-based BFR rehabilitation unsupervised exercise protocols(\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e38\u003c/span\u003e, \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e44\u003c/span\u003e, \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e46\u003c/span\u003e) generally demonstrated less significant improvements than supervised protocols did.(\u003cspan additionalcitationids=\"CR40 CR41 CR42\" citationid=\"CR38\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e43\u003c/span\u003e, \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e45\u003c/span\u003e, \u003cspan additionalcitationids=\"CR48\" citationid=\"CR46\" class=\"CitationRef\"\u003e47\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e49\u003c/span\u003e) This contrasts with findings from other reviews that combine exercise without BFR, suggesting that supervision and location do not directly determine final outcomes in ACL rehabilitation.(\u003cspan additionalcitationids=\"CR76\" citationid=\"CR74\" class=\"CitationRef\"\u003e75\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR76\" class=\"CitationRef\"\u003e77\u003c/span\u003e) Self application of BFR cuffs requires precise pressure settings and effective discomfort management, which may impact adherence and treatment effectiveness. Identifying key factors that enhance home-based interventions could be pivotal in optimizing their efficacy and reducing the socioeconomic costs associated with ACLR rehabilitation.\u003c/p\u003e \u003cp\u003eWhen evaluating the practical implementation and training parameters in experimental interventions via CERT scale(37), we identified a significant disparity. This inconsistency arises from the lack of a standardized framework for describing exercise parameters (FITT-VP)(\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e54\u003c/span\u003e) and BFR-RT methods. PRE-OP interventions for ACLR adhered to CERT criteria in 51.6% of the parameters, whereas POST-OP interventions followed them in 63.9%. This difference likely reflects a more developed research line in the POST-OP phase. However, PRE-OP interventions are being increasingly investigated,(\u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e78\u003c/span\u003e) with a focus on short-term adaptations to mitigate iatrogenic atrophy from the injury and surgery, ultimately aiming to \"prepare the leg for the storm\u0026rdquo;.(\u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e65\u003c/span\u003e) This contrasts with the longer interventions reported in POST-OP phases. The shorter duration of PRE-OP interventions may be associated with the limited time before surgery, which is often scheduled within weeks.(\u003cspan citationid=\"CR78\" class=\"CitationRef\"\u003e79\u003c/span\u003e) Although consensus on specific prehabilitation protocols for BFR-RE and ACLR remains limited, emerging research suggests that extended prehabilitation could lead to improved long-term outcomes in certain cases.(\u003cspan citationid=\"CR79\" class=\"CitationRef\"\u003e80\u003c/span\u003e) Notably, all PRE-OP studies incorporated open kinetic chain (OKC) exercises, whereas POST-OP studies predominantly utilized closed kinetic chain (CKC) exercises. This could be due to some articles suggesting that OKC exercises, such as single-leg extensions, may place significant strain on the ACL graft because of the lack of co-contraction between the quadriceps and hamstrings, potentially resulting in excessive anterior shear forces on the knee joint.(\u003cspan citationid=\"CR80\" class=\"CitationRef\"\u003e81\u003c/span\u003e, \u003cspan citationid=\"CR81\" class=\"CitationRef\"\u003e82\u003c/span\u003e) Meta-analyses indicate no definitive superiority between open and closed kinetic chain exercises after ACL reconstruction regarding knee laxity and overall outcomes.(\u003cspan citationid=\"CR81\" class=\"CitationRef\"\u003e82\u003c/span\u003e, \u003cspan citationid=\"CR82\" class=\"CitationRef\"\u003e83\u003c/span\u003e) In both open and closed kinetic chain exercises, load progression is crucial for effective rehabilitation. The reviewed articles suggest that BFR-LL may be beneficial in early ACLR phases, providing a safe way to increase loading.\u003c/p\u003e \u003cp\u003eGiven the pivotal role of exercise parameters in optimizing rehabilitation outcomes, the notion that exercise functions as medicine highlights the necessity of understanding its appropriate dosage and administration.(\u003cspan citationid=\"CR83\" class=\"CitationRef\"\u003e84\u003c/span\u003e) The lack of replicability in exercise parameters observed in our review is not unique; other reviews involving diverse pathologies(\u003cspan citationid=\"CR84\" class=\"CitationRef\"\u003e85\u003c/span\u003e) or PRE-OP ACLR patients(\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR85\" class=\"CitationRef\"\u003e86\u003c/span\u003e) have shown similar inconsistencies. Reporting these parameters is crucial for enhancing the replicability and transferability of findings to clinical practice. Consistent with the overall lack of reporting, none of the studies in our review that reached muscular failure reported on effort intensity relative to muscle failure proximity. This omission has physiological implications, as effort intensity can significantly influence physiological responses and adaptations. The studies included in our review yielded results such as systematic reviews examining training for muscular failure, which increases metabolic response, muscle damage, and perceived exertion while decreasing biomechanical properties.(\u003cspan citationid=\"CR86\" class=\"CitationRef\"\u003e87\u003c/span\u003e, \u003cspan citationid=\"CR87\" class=\"CitationRef\"\u003e88\u003c/span\u003e) Nonetheless, this approach provides gains in strength and muscle size comparable to non-failure training. Notably, applying BFR-LL to volitional failure yields similar results to LL-RT, but BFR-LL leads to earlier failure than does LL-RT,(45,89) reducing session volume(90) and duration. This makes BFR-LL a valuable option when reaching failure, which is an objective during rehabilitation stages.\u003c/p\u003e \u003cp\u003eWith respect to fatigue, intermittent BFR-RT has demonstrated strength gains comparable to continuous application but with reduced fatigue.(91,92) However, only one study utilized intermittent BFR-RT.(\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e43\u003c/span\u003e) Our scoping review, in contrast with previous reviews,(42,93) highlights a shift from using arbitrary pressures to more reliable methods for determining LOP, autoregulated devices, with automatic LOP measurement capability.(94,95) Ensuring optimal LOP is crucial for the efficacy and safety of BFR combined with exercise.(57,95,96) None of the studies included in our review reported adverse events, supporting Bond's assertion of a low risk of thromboembolism associated with BFR.(97) Notably, our study population typically excludes individuals at high risk for thromboembolism. To increase safety, clinicians should thoroughly screen for signs of venous thromboembolism, assess individual risks, and implement appropriate protocols when integrating BFR.\u003c/p\u003e \u003cdiv id=\"Sec20\" class=\"Section2\"\u003e \u003ch2\u003eLIMITATIONS\u003c/h2\u003e \u003cp\u003eOur scoping review identified several limitations in the current scientific literature on BFR combined with exercise and ACLR, as summarized in Table \u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e4\u003c/span\u003e.\u003c/p\u003e \u003cp\u003eA notable gap exists in studies applying BFR combined with endurance training for ACLR. The considerable heterogeneity in study designs complicates direct comparisons, whereas the limited number of studies affects overall comprehensiveness. Variations in BFR combined with exercise interventions, outcome measures, and exercise parameters significantly influence outcomes. Additionally, diverse measures and non-standarized follow-up further complicate synthesis and long-term effect assessment. The complexity of blinding therapists and subjects may introduce bias, and the lack of sham situations and intention-to-treat analyses further undermines the robustness of the findings. Poor reporting of exercise-related parameters also necessitates caution when interpreting results. Owing to the diversity of outcomes and parameters, conducting a meta-analysis was not feasible, and in some cases, data extraction from articles(\u003cspan additionalcitationids=\"CR40\" citationid=\"CR38\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e41\u003c/span\u003e, \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e43\u003c/span\u003e, \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e46\u003c/span\u003e) was not possible. A limitation of our review is the potential exclusion of relevant studies due to the omission of certain databases in the search process. Therefore, further studies are needed to explore long-term effects, adaptations, recovery, and reinjury rates of both PRE- and POST-OP interventions. To draw more definitive conclusions, further research with improved methodologies and patient follow-up is essential. Despite these challenges, the current literature underscores the growing importance of BFR-RT during PRE- and POST-OP phases for ACLR.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eIdentified knowledge gaps in literature and recommendations for future studies\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIdentified knowledge gaps from\u003c/p\u003e \u003cp\u003escoping review\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eImplications for future research\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLack of comparative studies and limited evidence\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLack of comparative studies directly comparing the effects BFR-RT on ACLR interventions to other exercise modalities or control/comparison groups. This limitation hampers our ability to comprehensively understand the advantages and disadvantages of BFR-RT in diverse populations and contexts.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLack of studies with diverse in participant populations\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eThe majority of BFR-RT and ACLR studies have primarily involved young and healthy participants without relevant pathologies or diseases beyond the ACL injury and concomitant meniscal procedures. Future research should prioritize addressing specific populations, such as conducting studies on specific sports, targeted age groups, and specific types of surgery interventions.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLack of understanding of the physiological mechanisms\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUnderstanding the underlying physiological mechanisms of the BFR-RT effect in ACLR recovery is crucial. Further research is needed to elucidate the specific responses and adaptations that occur with BFR-RT in ACLR rehabilitation. Investigating these mechanisms will provide a deeper understanding of how BFR-RT influences the healing and recovery process in ACL injuries.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLack of research on long-term effects\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLongitudinal studies on prolonged BFR-RT effects, specifically examining the long-term effects on muscle function, physical and physiological parameters, as well as potential adverse effects, is limited. More research is needed to understand the long-term effects of BFR-RT interventions.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLack of standardized protocols\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eThe absence of consensus on standardized BFR-RT protocols and parameters challenges the translation of findings. Establishing evidence-based guidelines for optimal BFR-RT protocols is crucial for enhancing consistency and facilitating effective implementation of BFR-RT.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLack of comparative studies and/or meta-analyses examining the dosage effects of -RT in ACLR:\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eThere is a need for comparative studies and/or future meta-analyses to elucidate the dosage effects of BFR-RT. This would help determine the optimal BFR-RT protocols and dosages for different populations and outcomes.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLack of standardized scales for assessing the methodological description of training and occlusion of BFR-RT.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eScales are needed to accurately describe and compare key BFR-RT parameters, enhancing research transparency and reproducibility.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLack of studies on the PRE-OP of BFR-RT application in ACLR:\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eThere is a lack of studies investigating the effects of PRE-OP BFR-RT application as part of rehabilitation following an ACL injury.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLack of standardized BFR devices\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eThere is a need for studies that compare different BFR devices, as currently, no device has been validated their methods for calculating the Limb Occlusion Pressure (LOP).\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"CONCLUSION","content":"\u003cp\u003eThe evidence examined demonstrates that the use of BFR-RT for ACLR holds significant promise in both PRE and POST-OP phases. In the PRE-OP phase, BFR-RT application significantly increased muscle strength and endurance and parameters linked to angiogenesis and transcriptional responses in comparison with LL-RT. Postoperatively, notable improvements in the BFR-RT group were observed in self-report questionnaires, knee pain, muscle volume, and muscle strength. When BFR-LL was compared with HL-RT, BFR-LL showed similar or greater improvements in functional measurements, muscle hypertrophy, and strength, although it also reported greater muscle pain during training. While home-based exercise interventions were feasible and well tolerated by patients, BFR-LL did not yield significant long-term results in comparison with LL-RT.\u003c/p\u003e \u003cp\u003eThe findings support the integration of BFR-RT into clinical practice, particularly during the early rehabilitation phases post-ACLR when weight-bearing activities are limited. BFR protocols can be adopted to enhance muscle strength and endurance while minimizing the risks of disuse atrophy. Clinicians should adopt a patient-centered perspective, tailoring BFR interventions to individual needs, ensuring both safety and comfort to maximize recovery benefits. Further research is needed to fully understand the physiological effects of BFR-RT in ACLR rehabilitation, validate existing findings, and establish precise parameters for clinical implementation. Additionally, more studies on BFR-ET are necessary to explore its potential benefits. Standardizing outcomes and methodologies, along with conducting additional randomized controlled trials with larger samples and extended follow-up periods, will enhance the understanding and integration of BFR-RT into clinical practice.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eACL, anterior cruciate ligament; ACLR, anterior cruciate ligament reconstruction; BC, body composition; BFR, blood flow restriction; BFR-LL, blood flow restriction light load; BFR-RT, blood flow restriction resistance training; BMD, bone mineral density; BMI, body mass index; BTB, bone-patella tendon-bone autograft; CBFR-HL, concentric blood flow restriction with heavy load; CG, comparison group; CKC, closed kinetic chain; CSA, cross-sectional area; DEXA, dual-energy X-ray absorptiometry; EBFR-HL, eccentric blood flow restriction with heavy load; FI, fatigue indexes; FITT-VP, frequency, intensity, type, time, volume, and progression; FM, functional measurements; HL-RT, high load resistance training; HS, hamstrings tendon; IG, intervention group; IKDC, International Knee Documentation Committee; IL, injured leg; KE, knee extension; KOOS, Knee Injury and Osteoarthritis Outcome Score; LEFS, Lower Extremity Functional Scale; LOP, limb occlusive pressure; M, man; MMHG, millimeters of mercury; MRI, magnetic resonance imaging; MPB, muscle physiology and biomarkers; MVIC, maximum voluntary isometric contraction; N, sample number; NMAR, neuromuscular adaptations and responses; N/S, not specified; OKC, open kinetic chain; POST, posterior; POST-OP, postoperative; PRE-OP, preoperative; QRCT, quasi-randomized controlled trial; QT, quadriceps tendon; RCT, randomized controlled trial; RM, repetition maximum; RPE, rate of perceived exertion; RTA, return to activity; RT, resistance training; SRQ, self-report questionnaires; VAS, visual analog scale; W, woman; y.o, years old.\u003c/p\u003e\n"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate:\u003c/strong\u003e Not applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication:\u003c/strong\u003e Not applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials:\u003c/strong\u003e Data and materials are included in the article.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests:\u003c/strong\u003e The authors certify that they have no affiliations with or financial involvement in any organization or entity with a direct financial interest in the subject matter or materials discussed in the article.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding:\u003c/strong\u003e Not applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026apos; contributions:\u0026nbsp;\u003c/strong\u003eRoger Fontanet designed and conducted the study, including the literature review, data analysis, and manuscript drafting. Eduardo Carballeira contributed to the methodological design, provided input on the study framework and statistical analysis, and reviewed the manuscript. Rafel Donat supervised the study, assisted with the methodological tools and techniques, and reviewed the manuscript. All authors approved the final version of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements:\u003c/strong\u003e Not applicable\u003c/p\u003e\n"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eChia L, De Oliveira Silva D, Whalan M, et al. Non-contact Anterior Cruciate Ligament Injury Epidemiology in Team-Ball Sports: A Systematic Review with Meta-analysis by Sex, Age, Sport, Participation Level, and Exposure Type. \u003cem\u003eSports Medicine\u003c/em\u003e. 2022;52(10):2447-2467. doi:10.1007/S40279-022-01697-W\u003c/li\u003e\n\u003cli\u003eSutherland K, Clatworthy M, Fulcher M, Chang K, Young SW. 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Low intensity blood flow restriction exercise: Rationale for a hypoalgesia effect. \u003cem\u003eMed Hypotheses\u003c/em\u003e. 2019;132:109370. doi:10.1016/J.MEHY.2019.109370\u003c/li\u003e\n\u003cli\u003eSong JS, Spitz RW, Yamada Y, et al. Exercise-induced hypoalgesia and pain reduction following blood flow restriction: A brief review. \u003cem\u003ePhysical Therapy in Sport\u003c/em\u003e. 2021;50:89-96. doi:10.1016/J.PTSP.2021.04.005\u003c/li\u003e\n\u003cli\u003eWalker A, Hing W, Lorimer A. The Influence, Barriers to and Facilitators of Anterior Cruciate Ligament Rehabilitation Adherence and Participation: a Scoping Review. \u003cem\u003eSports Med Open\u003c/em\u003e. 2020;6(1):1-22. doi:10.1186/S40798-020-00258-7\u003c/li\u003e\n\u003cli\u003eUchino S, Saito H, Okura K, Kitagawa T, Sato S. Effectiveness of a supervised rehabilitation compared with a home-based rehabilitation following anterior cruciate ligament reconstruction: A systematic review and meta-analysis. \u003cem\u003ePhysical Therapy in Sport\u003c/em\u003e. 2022;55:296-304. doi:10.1016/J.PTSP.2022.05.010\u003c/li\u003e\n\u003cli\u003eGamble AR, Pappas E, O\u0026rsquo;Keeffe M, Ferreira G, Maher CG, Zadro JR. Intensive supervised rehabilitation versus less supervised rehabilitation following anterior cruciate ligament reconstruction? A systematic review and meta-analysis. \u003cem\u003eJ Sci Med Sport\u003c/em\u003e. 2021;24(9):862-870. doi:10.1016/J.JSAMS.2021.03.003\u003c/li\u003e\n\u003cli\u003eKaya Utlu D. Description, Types, and Prescription of the Exercise. \u003cem\u003eFunctional Exercise Anatomy and Physiology for Physiotherapists\u003c/em\u003e. 2023:3-18. doi:10.1007/978-3-031-27184-7_1\u003c/li\u003e\n\u003cli\u003eGiesche F, Niederer D, Banzer W, Vogt L. Evidence for the effects of prehabilitation before ACL-reconstruction on return to sport-related and self-reported knee function: A systematic review. \u003cem\u003ePLoS One\u003c/em\u003e. 2020;15(10):e0240192. doi:10.1371/JOURNAL.PONE.0240192\u003c/li\u003e\n\u003cli\u003eSubirats Bayego E, Subirats Vila G, Soteras Mart\u0026iacute;nez I. [Exercise prescription: indications, dosage and side effects]. \u003cem\u003eMed Clin (Barc)\u003c/em\u003e. 2011;138(1):18-24. doi:10.1016/J.MEDCLI.2010.12.008\u003c/li\u003e\n\u003cli\u003eHansford HJ, Wewege MA, Cashin AG, et al. If exercise is medicine, why don\u0026rsquo;t we know the dose? An overview of systematic reviews assessing reporting quality of exercise interventions in health and disease. \u003cem\u003eBr J Sports Med\u003c/em\u003e. 2022;56(12):692-700. doi:10.1136/BJSPORTS-2021-104977\u003c/li\u003e\n\u003cli\u003eCarter HM, Littlewood C, Webster KE, Smith BE. The effectiveness of preoperative rehabilitation programmes on postoperative outcomes following anterior cruciate ligament (ACL) reconstruction: A systematic review. \u003cem\u003eBMC Musculoskelet Disord\u003c/em\u003e. 2020;21(1):1-13. doi:10.1186/S12891-020-03676-6\u003c/li\u003e\n\u003cli\u003eRefalo MC, Helms ER, Hamilton DL, Fyfe JJ. Influence of Resistance Training Proximity-to-Failure, Determined by Repetitions-in-Reserve, on Neuromuscular Fatigue in Resistance-Trained Males and Females. \u003cem\u003eSports Med Open\u003c/em\u003e. 2023;9(1). doi:10.1186/S40798-023-00554-Y\u003c/li\u003e\n\u003cli\u003eGrgic J, Schoenfeld BJ, Orazem J, Sabol F. Effects of resistance training performed to repetition failure or non-failure on muscular strength and hypertrophy: A systematic review and meta-analysis. \u003cem\u003eJ Sport Health Sci\u003c/em\u003e. 2022;11(2):202-211. doi:10.1016/J.JSHS.2021.01.007\u003c/li\u003e\n\u003cli\u003eSieljacks P, Degn R, Hollaender K, Wernbom M, Vissing K. Non-failure blood flow restricted exercise induces similar muscle adaptations and less discomfort than failure protocols. \u003cem\u003eScand J Med Sci Sports\u003c/em\u003e. 2019;29(3):336-347. doi:10.1111/SMS.13346\u003c/li\u003e\n\u003cli\u003eHusmann F, Mittlmeier T, Bruhn S, Zschorlich V, Behrens M. Impact of Blood Flow Restriction Exercise on Muscle Fatigue Development and Recovery. \u003cem\u003eMed Sci Sports Exerc\u003c/em\u003e. 2018;50(3):436-446. doi:10.1249/MSS.0000000000001475\u003c/li\u003e\n\u003cli\u003eFreitas EDS, Miller RM, Heishman AD, Aniceto RR, Silva JGC, Bemben MG. Perceptual responses to continuous versus intermittent blood flow restriction exercise: A randomized controlled trial. \u003cem\u003ePhysiol Behav\u003c/em\u003e. 2019;212:112717. doi:10.1016/J.PHYSBEH.2019.112717\u003c/li\u003e\n\u003cli\u003eYasuda T, Loenneke J, Ogasawara R, Abe T. Influence of continuous or intermittent blood flow restriction on muscle activation during low-intensity multiple sets of resistance exercise. \u003cem\u003eActa Physiol Hung\u003c/em\u003e. 2013;100(4):419-426. doi:10.1556/APHYSIOL.100.2013.4.6\u003c/li\u003e\n\u003cli\u003eCaetano D, Oliveira C, Correia C, Barbosa P, Montes A, Carvalho P. Rehabilitation outcomes and parameters of blood flow restriction training in ACL injury: A scoping review. \u003cem\u003ePhysical Therapy in Sport\u003c/em\u003e. 2021;49:129-137. doi:10.1016/J.PTSP.2021.01.015\u003c/li\u003e\n\u003cli\u003eMcEwen JA, Owens JG, Jeyasurya J. Why is it Crucial to Use Personalized Occlusion Pressures in Blood Flow Restriction (BFR) Rehabilitation? \u003cem\u003eJ Med Biol Eng\u003c/em\u003e. 2019;39(2):173-177. doi:10.1007/S40846-018-0397-7/FIGURES/3\u003c/li\u003e\n\u003cli\u003eJacobs E, Rolnick N, Wezenbeek E, et al. Investigating the autoregulation of applied blood flow restriction training pressures in healthy, physically active adults: an intervention study evaluating acute training responses and safety. \u003cem\u003eBr J Sports Med\u003c/em\u003e. 2023:bjsports-2022-106069. doi:10.1136/BJSPORTS-2022-106069\u003c/li\u003e\n\u003cli\u003eCaetano D, Oliveira C, Correia C, Barbosa P, Montes A, Carvalho P. Rehabilitation outcomes and parameters of blood flow restriction training in ACL injury: A scoping review. \u003cem\u003ePhysical Therapy in Sport\u003c/em\u003e. 2021;49:129-137. doi:10.1016/J.PTSP.2021.01.015\u003c/li\u003e\n\u003cli\u003eBond CW, Hackney KJ, Brown SL, Noonan BC. Blood Flow Restriction Resistance Exercise as a Rehabilitation Modality Following Orthopedic Surgery: A Review of Venous Thromboembolism Risk. \u003cem\u003ehttps://doi.org/102519/jospt20198375\u003c/em\u003e. 2018;49(1):17-27. doi:10.2519/JOSPT.2019.8375\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTables 2 and 3 are available in the Supplementary Files section.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"University of Vic","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Anterior cruciate ligament reconstruction, blood flow restriction, preoperative rehabilitation, postoperative rehabilitation, exercise parameters","lastPublishedDoi":"10.21203/rs.3.rs-6062247/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6062247/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAnterior cruciate ligament injuries often lead to muscle atrophy and prolonged recovery following anterior cruciate ligament reconstruction (ACLR). Blood flow restriction (BFR) has emerged as a strategy to optimize neuromuscular adaptations with lower loads, potentially enhancing rehabilitation outcomes in both preoperative and postoperative phases. This review aims to comprehensively evaluate the comparative effectiveness of BFR applied during resistance and endurance exercises versus non-BFR protocols, both before and after ACLR, while also examining key training parameters and BFR protocols to guide further research and clinical practice.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eLiterature search\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA comprehensive literature search was conducted across multiple databases, including WoS, PEDro, Scopus, PUBMED (MEDLINE), SportDiscus, and the Cochrane Library, covering publications from inception to January 22, 2025. Studies eligible for inclusion were randomized controlled trials and quasi-randomized controlled trials that compared BFR interventions with non-BFR training in patients undergoing ACLR. Data synthesis followed the Preferred Reporting Items for Systematic Reviews and Meta-analysis extension for Scoping Reviews. The PEDro and CERT scales were used to assess the methodological quality of the included studies. Detailed training parameters and cuff specifications were extracted and summarized in tables.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFifteen of the initial 385 articles identified met the eligibility criteria and were included in the final analysis, comprising a sample of 417 patients. Outcomes were categorized into six areas: body composition, neuromuscular responses and adaptations, self-report questionnaires, functional measures, muscle physiology and biomarkers, and return to activity. Five articles focused on preoperative interventions, nine on postoperative interventions, and one addressed both phases.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis review suggests that BFR resistance training is an effective tool in the preoperative and postoperative phases of ACLR. Additionally, it can help improve muscle size, strength, functional measurements, body composition, muscle blood flow, and subjective perceptions.\u003c/p\u003e","manuscriptTitle":"Blood Flow Restriction Training Prior to and After Anterior Cruciate Ligament Reconstruction: A Scoping review","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-02-21 17:01:13","doi":"10.21203/rs.3.rs-6062247/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"3d4f4907-33cc-4f77-8443-b87118eb4112","owner":[],"postedDate":"February 21st, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":44607963,"name":"Physical Medicine \u0026 Rehab"},{"id":44607964,"name":"Sports Medicine and Kinesiology"}],"tags":[],"updatedAt":"2025-02-21T17:01:13+00:00","versionOfRecord":[],"versionCreatedAt":"2025-02-21 17:01:13","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6062247","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6062247","identity":"rs-6062247","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}