Effects of Early Rehabilitation Using Blood Flow Restriction and/or Surface Electromyography Biofeedback on Quadriceps Activation and Strength After Anterior Cruciate Ligament Reconstruction: A Multicenter Randomized Controlled Trial

Haute Ecole ARC Sante

Status: Not yet enrolling

Conditions: Knee Injuries; Anterior Cruciate Ligament Injuries; Muscle Weakness

Treatments: Behavioral: Standard Rehabilitation; Behavioral: sEMG Biofeedback; Behavioral: Blood Flow Restriction (BFR) Training

Study type: Interventional

Funder types: Other

Identifiers

NCT07145606

AMIRACL

Details and patient eligibility

About

Many patients experience quadriceps inhibition after anterior cruciate ligament (ACL) reconstruction, delaying strength recovery, hindering return to sport, and potentially increasing the risk of re-injury. Two rehabilitation strategies-low-load blood flow restriction (BFR) training and surface electromyography (sEMG) biofeedback-aim to enhance neuromuscular activation and strength while limiting joint load. However, comparative and combined evidence in pragmatic, multicenter settings remains limited.

AMIRACL is a multicenter, prospective, randomized, controlled, parallel-group trial with four arms enrolling 200 adults (18-35 years) undergoing a first-time ACL reconstruction. Participants are randomized with center stratification; outcome assessors are blinded to allocation. The four groups are: (1) standard rehabilitation; (2) standard + early BFR; (3) standard + early sEMG biofeedback; and (4) standard + combined BFR and sEMG biofeedback. Interventions begin about 2 weeks postoperatively, are delivered over 6 weeks at three supervised sessions per week, and are integrated into contemporary ACL rehabilitation. BFR uses individualized, auto-regulated cuff pressure during low-load isometric and then dynamic exercises. sEMG biofeedback provides real-time visual and/or auditory feedback to optimize quadriceps recruitment during targeted tasks. The combined arm receives both modalities concurrently.

The primary objective is to compare quadriceps activation (sEMG) and maximal isometric knee extensor strength between groups at 3 and 6 months. Secondary objectives include return-to-sport readiness and patient-reported function (e.g., ACL-RSI, IKDC), broader knee outcomes (e.g., KOOS, Lysholm), adherence and adverse events across arms, and ACL re-injury (ipsilateral graft rupture or contralateral ACL injury) within 2 years. Longer-term patient-reported quality of life is explored up to 5 years.

Key eligibility criteria include age 18-35 years, first ACL reconstruction, and preinjury sport participation; major exclusions include revision ACL surgery, concomitant multi-ligament repair, neuromuscular disorders, and contraindications to BFR or sEMG. The planned sample size is 200 (50 per arm), powered to detect a clinically meaningful between-group difference in quadriceps activation. Analyses will follow the intention-to-treat principle using mixed-effects models for repeated measures. The study is conducted under Good Clinical Practice and applicable Swiss regulations; all participants provide written informed consent. Overall, AMIRACL will determine whether early BFR, sEMG biofeedback, or their combination meaningfully improves quadriceps activation, strength, and clinical recovery after ACL reconstruction compared with standard rehabilitation alone.

Enrollment: 200 estimated patients

Sex: All

Ages: 18 to 35 years old

Volunteers: No Healthy Volunteers

Inclusion criteria

• Adults aged 18-35 years.

First-time anterior cruciate ligament (ACL) reconstruction.

Pre-injury activity level Tegner ≥ 6.

Marx activity scale ≥ 12.

Body mass index < 35.

With or without associated meniscal injury.

Exclusion criteria

• Revision ACL surgery.

Concurrent repair of other knee ligaments.

Neurological or systemic musculoskeletal disorders.

Contraindications to blood flow restriction (BFR) or surface EMG monitoring/biofeedback.

Pregnancy or lactation.

Language barrier or cognitive impairment preventing valid informed consent; vulnerable populations not enrolled.

Trial design

Primary purpose: Treatment

Allocation: Randomized

Interventional model: Parallel Assignment

Masking: Single Blind

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200 participants in 4 patient groups

Standard Rehabilitation

Active Comparator group

Description:

Participants receive the standardized postoperative ACL rehabilitation program only. Sessions are supervised approximately 3 times per week for 6 weeks, starting about 2 weeks after surgery. Content includes progressive range of motion, quadriceps activation and strengthening, functional tasks, and return-to-activity progressions delivered per protocol.

Treatment:

Behavioral: Standard Rehabilitation

Standard Rehabilitation + Blood Flow Restriction (BFR)

Experimental group

Description:

Participants receive the standardized postoperative ACL rehabilitation plus low-load BFR training. BFR is applied with individualized limb occlusion pressure during prescribed isometric and then dynamic exercises. Sessions are supervised \~3 times per week for 6 weeks beginning \~2 weeks postoperatively.

Treatment:

Behavioral: Blood Flow Restriction (BFR) Training

Standard Rehabilitation + sEMG Biofeedback

Experimental group

Description:

Participants receive the standardized postoperative ACL rehabilitation plus surface EMG biofeedback to optimize quadriceps recruitment during targeted tasks (e.g., isometric contractions and functional movements). Real-time visual and/or auditory feedback is provided during supervised sessions \~3 times per week for 6 weeks starting \~2 weeks after surgery.

Treatment:

Behavioral: sEMG Biofeedback

Standard Rehabilitation + Combined BFR and sEMG Biofeedback

Experimental group

Description:

Participants receive the standardized postoperative ACL rehabilitation with both adjuncts delivered concurrently: individualized low-load BFR training and sEMG biofeedback during targeted tasks. Sessions are supervised \~3 times per week for 6 weeks beginning \~2 weeks postoperatively.

Treatment:

Behavioral: Blood Flow Restriction (BFR) Training

Behavioral: sEMG Biofeedback