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

Summary

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.

Conditions

• Anterior Cruciate Ligament Injuries
• Knee Injuries
• Muscle Weakness

Interventions

BEHAVIORAL

Standard Rehabilitation

Standardized postoperative ACL rehabilitation only. Begins \~2 weeks after surgery; supervised \~3 sessions/week for 6 weeks. Includes progressive range of motion, quadriceps activation/strengthening, functional drills, and return-to-activity progressions delivered per protocol.

BEHAVIORAL

Blood Flow Restriction (BFR) Training

Low-load resistance exercises performed with individualized limb occlusion pressure (LOP) determined each session; target %LOP per protocol. Progresses from isometric to dynamic open/closed-chain tasks. Delivered under supervision \~3 sessions/week for 6 weeks; monitoring of tolerance and adverse events per safety LOP.

BEHAVIORAL

sEMG Biofeedback

Real-time surface electromyography biofeedback to optimize quadriceps recruitment during targeted tasks (e.g., isometric contractions, straight-leg raise, sit-to-stand, mini-squat, gait drills). Visual and/or auditory feedback with progressive targets. Supervised \~3 sessions/week for 6 weeks; outcome assessors remain blinded.

Sponsors & Collaborators

• Haute Ecole ARC Sante

  lead OTHER

Study Design

Allocation

RANDOMIZED

Purpose

TREATMENT

Masking

SINGLE

Model

PARALLEL

Eligibility

Min Age

18 Years

Max Age

35 Years

Sex

ALL

Healthy Volunteers

No

Timeline & Regulatory

Start

2026-01-02

Primary Completion

2026-04-02

Completion

2031-01-02

Countries

• France
• Switzerland

Study Locations