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

NCT07145606 | Not Yet Recruiting

• 1 other identifier: AMIRACL
• Study Type: interventional
• Target: 200
• Locations: 2 countries
• Sites: 4

Brief 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

Keywords

Anterior Cruciate Ligament; ACL Reconstruction; Knee Injuries; Rehabilitation; Quadriceps Muscle; Quadriceps Activation; Muscle Strength; Arthrogenic Muscle Inhibition; Blood Flow Restriction Training; Surface Electromyography; Biofeedback; Return to Sport

Outcome Measures

Primary Outcomes (2)

• Quadriceps neuromuscular activation (surface EMG)

  Mean normalized surface electromyography (sEMG) activity of the quadriceps during standardized voluntary isometric knee extension; higher values indicate greater activation. Primary analysis compares groups at 3 and 6 months; baseline and post-intervention values are collected to describe trajectories.

  3 months and 6 months after ACL reconstruction

• Maximal isometric knee extensor strength (traction dynamometry)

  Peak voluntary isometric knee extension strength recorded with a traction dynamometer under standardized positioning; primary analysis compares groups at 3 and 6 months; baseline and post-intervention values are collected to describe trajectories.

  3 months and 6 months after ACL reconstruction

Secondary Outcomes (5)

• ACL-RSI (Return to Sport after Injury)

  3 months and 6 months after ACL reconstruction

• IKDC (International Knee Documentation Committee) subjective knee form

  3 months and 6 months after ACL reconstruction

• ACL re-injury/recurrence rate

  24 months after ACL reconstruction (telephone follow-up)

• KOOS (Knee injury and Osteoarthritis Outcome Score)

  5 years after ACL reconstruction

• Lysholm Knee Scoring Scale

  5 years after ACL reconstruction

Other Outcomes (3)

• Quadriceps neuromuscular activation (sEMG) at end of intervention

  Week 8 (post-intervention)

• Maximal isometric knee extensor strength at end of intervention

  Week 8 (post-intervention)

• Adverse events related to rehabilitation and/or BFR/sEMG procedures

  Throughout the 6-week intervention and up to Month 6 follow-up

Study Arms (4)

Standard Rehabilitation

ACTIVE COMPARATOR

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.

Behavioral: Standard Rehabilitation

Standard Rehabilitation + Blood Flow Restriction (BFR)

EXPERIMENTAL

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.

Behavioral: Blood Flow Restriction (BFR) Training

Standard Rehabilitation + sEMG Biofeedback

EXPERIMENTAL

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.

Behavioral: sEMG Biofeedback

Standard Rehabilitation + Combined BFR and sEMG Biofeedback

EXPERIMENTAL

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.

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

Interventions

Standard Rehabilitation BEHAVIORAL

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.

Standard Rehabilitation

Blood Flow Restriction (BFR) Training BEHAVIORAL

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.

Standard Rehabilitation + Blood Flow Restriction (BFR); Standard Rehabilitation + Combined BFR and sEMG Biofeedback

sEMG Biofeedback BEHAVIORAL

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.

Standard Rehabilitation + Combined BFR and sEMG Biofeedback; Standard Rehabilitation + sEMG Biofeedback

Eligibility Criteria

• Age: 18 Years - 35 Years
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64)

You may qualify if:

• 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.

You may not qualify if:

• 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.

Sponsors & Collaborators

• Haute Ecole ARC Sante: lead

Study Sites (4)

Orthosport

Domont, France

Location

Movare

Bulle, Switzerland

Location

Centre de l'Appareil Locomoteur et du Sport, Hôpitaux Universitaires de Genève (HUG)

Geneva, Switzerland

Location

Exotherapie

Geneva, Switzerland

Location

MeSH Terms

Conditions

Anterior Cruciate Ligament Injuries; Knee Injuries; Muscle Weakness

Interventions

Blood Flow Restriction Therapy

Condition Hierarchy (Ancestors)

Leg Injuries; Wounds and Injuries; Muscular Diseases; Musculoskeletal Diseases; Neuromuscular Manifestations; Neurologic Manifestations; Nervous System Diseases; Pathologic Processes; Pathological Conditions, Signs and Symptoms; Signs and Symptoms

Intervention Hierarchy (Ancestors)

Exercise Therapy; Rehabilitation; Aftercare; Continuity of Patient Care; Patient Care; Therapeutics; Physical Therapy Modalities

Central Study Contacts

Florian Forelli, PhD

CONTACT

0041329301654; florian.forelli@he-arc.ch

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: SINGLE
• Who Masked: OUTCOMES ASSESSOR
• Purpose: TREATMENT
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Assistant Professor ; PhD

Study Record Dates

• First Submitted: August 21, 2025
• First Posted: August 28, 2025
• Study Start: January 2, 2026
• Primary Completion: April 2, 2026
• Study Completion (Estimated): January 2, 2031
• Last Updated: August 28, 2025

Record last verified: 2025-08

Data Sharing

• IPD Sharing: Will share
• Shared Documents: STUDY PROTOCOL, SAP, ICF

Locations

FR (1); CH (3)