The goal of this clinical trial is to determine whether blood flow restriction resistance training (BFR-RT) improves postoperative muscle recovery and functional outcomes following primary surgical repair of acute Achilles tendon rupture (ATR) in adults undergoing standard rehabilitation. The main questions it aims to answer are:

Does patient-specific BFR-RT improve ankle plantarflexion strength recovery compared with sham BFR-RT or standard rehabilitation alone?

Does BFR-RT improve gastrocnemius-soleus muscle morphology and patient-reported functional outcomes following ATR repair?

Researchers will compare (1) BFR-RT combined with standard physical therapy, (2) sham BFR-RT combined with standard physical therapy, and (3) standard physical therapy alone to determine whether BFR-RT enhances muscle recovery, functional outcomes, and return-to-activity timelines following surgical ATR repair.

Participants will:

Be randomized to BFR-RT + standard physical therapy, sham BFR-RT + standard physical therapy, or standard physical therapy alone

Perform supervised rehabilitation exercises using a personalized tourniquet system calibrated to limb occlusion pressure (LOP) depending on group allocation

Undergo isometric ankle plantarflexion strength testing using the Fysiometer platform

Receive ultrasound imaging of the gastrocnemius-soleus complex to assess muscle cross-sectional area

Complete patient-reported outcome measures assessing pain and physical function

Attend follow-up evaluations at 6 weeks, 3 months, 4.5 months, 6 months, and 12 months postoperatively

Achilles tendon rupture (ATR) is a common musculoskeletal injury that frequently results in prolonged functional impairment despite successful surgical repair. Even with modern operative techniques and standardized rehabilitation protocols, many patients demonstrate persistent weakness of the gastrocnemius-soleus complex, deficits in ankle plantarflexion strength, and delayed return to activity. These deficits are thought to arise from a combination of postoperative immobilization, restricted early loading, and muscle atrophy during the early phases of recovery. Conventional postoperative rehabilitation protocols typically emphasize gradual progression of low-load resistance training to protect the healing tendon. While these protocols prioritize tendon safety, they may provide insufficient mechanical and metabolic stimulus to promote optimal muscle hypertrophy and neuromuscular recovery during the early postoperative period.

Blood flow restriction resistance training (BFR-RT) has emerged as a potential strategy to enhance muscular adaptation while using low mechanical loads. By applying controlled external pressure to the proximal limb during exercise, BFR-RT produces localized hypoxia and metabolic stress that can stimulate anabolic signaling pathways associated with muscle hypertrophy and strength gains. Prior studies in orthopedic and sports rehabilitation settings-including anterior cruciate ligament reconstruction and chronic Achilles tendinopathy-have demonstrated that low-load BFR-RT can produce physiologic adaptations comparable to traditional high-load resistance training while minimizing mechanical stress on healing tissues. However, the efficacy and safety of BFR-RT during the early rehabilitation period following primary ATR repair have not been evaluated in a prospective randomized clinical trial.

This study is designed as a prospective, three-arm randomized controlled trial to evaluate whether integrating BFR-RT into postoperative ATR rehabilitation improves early muscle recovery and functional outcomes while maintaining an acceptable safety profile. Participants undergoing primary surgical repair for an acute unilateral mid-portion ATR will be randomized to one of three rehabilitation protocols: BFR-RT combined with standard physical therapy, sham BFR-RT combined with standard physical therapy, or standard physical therapy alone. The BFR intervention will be delivered using a personalized tourniquet system that determines limb occlusion pressure for each participant to standardize vascular restriction and minimize inter-individual variability in occlusion levels.

Participants will undergo standardized postoperative rehabilitation and will be followed longitudinally over a 12-month recovery period. Clinical assessments will be performed at predefined postoperative intervals to evaluate physiologic recovery of the gastrocnemius-soleus complex and patient-centered functional outcomes. Safety monitoring will include systematic documentation of potential adverse events associated with postoperative rehabilitation or vascular restriction techniques.

By evaluating the physiologic and clinical effects of patient-specific BFR-RT following surgical ATR repair, this study aims to generate evidence regarding whether low-load metabolic training can safely accelerate muscle recovery and improve functional rehabilitation outcomes in this population. Findings from this trial may inform future postoperative rehabilitation protocols and help define the role of BFR-RT as an adjunctive strategy in tendon repair recovery pathways.

Inclusion Criteria

• Adults aged 18 to 75 years
• Acute unilateral midportion Achilles tendon rupture
• Primary surgical repair performed within 2 weeks of injury
• Willingness and ability to comply with the postoperative rehabilitation protocol and follow-up schedule

Exclusion Criteria:

• Cognitive impairment or inability to follow study instructions
• Planned postoperative follow-up at another institution
• Use of fluoroquinolone antibiotics or systemic corticosteroids within the past 6 months
• Previous Achilles tendon rupture in either limb
• Simultaneous bilateral Achilles tendon rupture
• History of venous thromboembolism (deep venous thrombosis or pulmonary embolism)
• Diabetes mellitus
• Reduced lower extremity function due to conditions other than Achilles tendon rupture
• Uncontrolled hypertension
• Peripheral vascular disease or ankle-brachial index less than 1.0
• Chronic kidney disease or heart failure with lower extremity edema
• Lower extremity dialysis access
• Lower extremity thrombophlebitis
• Active cancer or ongoing chemotherapy treatment
• Prior lymphadenectomy
• Tumor or malignancy affecting the lower extremities
• Hemophilia or other major bleeding disorders
• Factor V Leiden mutation or known thrombophilia
• Sickle cell anemia
• Pregnancy
• Surgery within the previous month

There are no current plans to share individual participant data. Data generated in this investigator-initiated study are subject to institutional data governance and participant privacy protections, and the study team has elected not to make IPD publicly available at this time.