{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,15]],"date-time":"2026-09-15T03:31:08Z","timestamp":1789443068870,"version":"build-2803163510"},"reference-count":34,"publisher":"International Journal of Sports Physical Therapy","issue":"6","license":[{"start":{"date-parts":[[2026,6,1]],"date-time":"2026-06-01T00:00:00Z","timestamp":1780272000000},"content-version":"unspecified","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"abstract":"\n Background<\/jats:title>\n Arthrogenic muscle inhibition (AMI) after anterior cruciate ligament reconstruction (ACLR) is a major barrier to muscle recovery, but early (within the first ~2 weeks after surgery) neuromuscular profiles remain poorly quantified. Excessive hamstring co-activation, a common compensatory response to quadriceps inhibition, may further compromise knee mechanics and rehabilitation outcomes.<\/jats:p>\n Hypothesis\/Purpose: The primary objective of this study was to compare early quadriceps activation and quadriceps\/hamstring co-activation patterns between individuals following ACLR and matched healthy controls (CTRL). The secondary objective was to determine whether these neuromuscular alterations were present bilaterally, affecting both the operated and non-operated limbs. It was hypothesized that individuals post-ACLR would demonstrate reduced voluntary quadriceps activation and increased hamstring co-activation compared to CTRL, as well as bilateral neuromuscular alterations within the ACLR group.<\/jats:p>\n <\/jats:sec>\n \n Study Design<\/jats:title>\n Cross-sectional case\u2013control study.<\/jats:p>\n <\/jats:sec>\n \n Methods<\/jats:title>\n Thirty males (15 primary unilateral ACLR with hamstring autograft, 15 healthy controls) were assessed 15.3 \u00b1 0.7 days after ACLR (pre-injury Tegner Activity Scale: 7 \u00b1 1). Inclusion criteria required a Stroke Test score < 1+ and no passive extension deficit, defined by SANTI (Scientific Anterior Cruciate Ligament Network International) classification of AMI type 1-2. Participants performed three 5-second maximal voluntary isometric knee extensions (MVIC) in supine position with the knee fully extended; no sEMG normalization was performed, and raw RMS values were used for analysis. Surface electromyography (sEMG) was recorded from vastus lateralis (VL), vastus medialis (VM), biceps femoris (BF), and medial hamstrings (MH) at 1000 Hz; mean Root Mean Square (RMS) values were then computed over a 3-s stable plateau window of each MVIC and used for analysis. Co-activation Indices (CoI) were calculated for the agonist\u2013antagonist pairs VL\u2013BF, VM\u2013BF, VL\u2013MH, and VM\u2013MH. ACLR group versus CTRL was via independent-samples t-tests, and intra-individual ACLR group comparisons (operated vs.\u00a0non operated limb) via paired-samples t-tests. Effect sizes (Hedges\u2019 g for between-group, Cohen\u2019s d for paired comparisons; rank-biserial correlation for non-parametric tests) were reported with 95% confidence intervals.<\/jats:p>\n <\/jats:sec>\n \n Results<\/jats:title>\n Significantly lower mean values were found in the operated limb of the ACLR group compared to CTRL for VL (4.15 \u00b1 2.24 vs 7.89 \u00b1 1.50 \u03bcV, p < 0.001), VM (4.07 \u00b1 2.25 vs 9.07 \u00b1 1.24 \u03bcV, p < 0.001), and BF (3.73 \u00b1 2.64 vs 5.79 \u00b1 3.56 \u03bcV, p = 0.011). In the operated limb, all CoI were significantly higher (all p < 0.001) in the ACLR group than in CTRL for VL\u2013BF (47.77 \u00b1 9.92% vs 32.07 \u00b1 9.32%), VM\u2013BF (48.83 \u00b1 8.98% vs 29.10 \u00b1 5.45%), VL\u2013MH (49.83 \u00b1 11.58% vs 31.08 \u00b1 6.78%), and VM\u2013MH (48.17 \u00b1 9.38% vs 29.11 \u00b1 5.69%). Intra-individual and contralateral comparisons showed that the ACLR group presented with significantly higher CoI in the non-operated limb compared to CTRL for VL\u2013MH (36.1 \u00b1 5.1% vs 29.9 \u00b1 6.0%, p = 0.018) and VM\u2013MH (35.7 \u00b1 5.9% vs 28.4 \u00b1 4.9%, p < 0.001). No significant between-group differences were found for MH activation (p = 0.250).<\/jats:p>\n <\/jats:sec>\n \n Conclusion<\/jats:title>\n Within the first 15.3 \u00b1 0.7 days after ACLR, subjects who had undergone ACLR showed markedly reduced voluntary quadriceps activation associated with increased, bilateral hamstring co-activation, in both the operated and non-operated limb.<\/jats:p>\n <\/jats:sec>\n \n Level of Evidence<\/jats:title>\n Level 3, cross-sectional case\u2013control study.<\/jats:p>\n <\/jats:sec>","DOI":"10.26603\/001c.162263","type":"journal-article","created":{"date-parts":[[2026,6,1]],"date-time":"2026-06-01T13:25:03Z","timestamp":1780320303000},"source":"Crossref","is-referenced-by-count":1,"title":["Early Neuromuscular and Co-activation Patterns After Anterior Cruciate Ligament Reconstruction In Males: A Case-control Exploratory Feasibility Study"],"prefix":"10.26603","volume":"21","author":[{"given":"Roberto","family":"Ricupito","sequence":"first","affiliation":[{"name":"Restart Physiotherapy, Via felice grossi Gondi 35, Rome, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Marco","family":"Bravi","sequence":"additional","affiliation":[{"name":"Physical Medicine and Rehabilitation Unit, Campus Bio-Medico University, Via Alvaro Del Portillo 200, 00128, Rome, Italy"},{"name":"Rehabilitation, Fondazione Policlinico Universitario Campus Bio-Medico, Via Alvaro Del Portillo 200, 00128, Rome, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Fabio","family":"Santacaterina","sequence":"additional","affiliation":[{"name":"Physical Medicine and Rehabilitation Unit, Campus Bio-Medico University, Via Alvaro Del Portillo 200, 00128, Rome, Italy"},{"name":"Rehabilitation, Fondazione Policlinico Universitario Campus Bio-Medico, Via Alvaro Del Portillo 200, 00128, Rome, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Alessandro","family":"Carrozzo","sequence":"additional","affiliation":[{"name":"Centre Orthop\u00e9dique Santy, Ramsay G\u00e9n\u00e9rale de Sant\u00e9, FIFA Medical Centre of Excellence, Lyon, France"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Rosalba","family":"Castellucci","sequence":"additional","affiliation":[{"name":"PT, private clinic, Via Maiella, Montalbano Jonico, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Giandomenico","family":"Campardo","sequence":"additional","affiliation":[{"name":"Private Clinic, Via San Marco 10, Pordenone, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Marco","family":"Ceserani","sequence":"additional","affiliation":[{"name":"Private clinic, Via Domenico Ragona 41 00143, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Federica","family":"Bressi","sequence":"additional","affiliation":[{"name":"Physical Medicine and Rehabilitation Unit, Campus Bio-Medico University, Via Alvaro Del Portillo 200, 00128, Rome, Italy"},{"name":"Rehabilitation, Fondazione Policlinico Universitario Campus Bio-Medico, Via Alvaro Del Portillo 200, 00128, Rome, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Rocco","family":"Papalia","sequence":"additional","affiliation":[{"name":"Fondazione Policlinico Universitario Campus Bio-Medico, Roma, Italy"},{"name":"Research Unit of Orthopaedic and Trauma Surgery, Department of Medicine and Surgery, Universit\u00e0 Campus Bio-Medico di Roma, Roma, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sebastiano","family":"Vasta","sequence":"additional","affiliation":[{"name":"Fondazione Policlinico Universitario Campus Bio-Medico, Roma, Italy"},{"name":"Research Unit of Orthopaedic and Trauma Surgery, Department of Medicine and Surgery, Universit\u00e0 Campus Bio-Medico di Roma, Roma, Italy"},{"name":"Department of Movement, Human and Health Sciences, University of Rome \u201cForo Italico,\u201d Rome, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8650-2746","authenticated-orcid":true,"given":"Florian","family":"Forelli","sequence":"additional","affiliation":[{"name":"Haute-Ecole Arc Sant\u00e9, HES-SO University of Applied Sciences and Arts Western Switzerland, 2800 Del\u00e9mont, Switzerland"},{"name":"Orthopaedic Surgery Department, Clinic of Domont, Ramsay Healthcare, OrthoLab, 95330 Domont, France"},{"name":"Soci\u00e9t\u00e9 Fran\u00e7aise des Masseurs\u2014Kin\u00e9sith\u00e9rapeutes du Sport Lab, 93380 Pierrefite sur Seine, France"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"11140","published-online":{"date-parts":[[2026,6,1]]},"reference":[{"issue":"1","key":"ref1","doi-asserted-by":"publisher","first-page":"87","DOI":"10.4085\/1062-6050-45.1.87","article-title":"Quadriceps activation following knee injuries: a systematic review","volume":"45","author":"J. 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