Project Tendura: The Impact of Blood Flow Restriction Resistance Training (BFR-RT) in Patients With Achilles Tendon Rupture (ATR) Repair

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

Study Overview

• Status: Active, not recruiting
• Conditions: Achilles Tendon Rupture; Achilles Tendon Repairs/Reconstructions; Blood Flow Restriction Therapy; Dynamic Blood Flow Restriction
• Intervention / Treatment: Device: Blood Flow Restriction Resistance Training (BFR-RT); Behavioral: Standard Physical Therapy; Device: Sham Blood Flow Restriction

Detailed Description

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.

• Study Type: Interventional
• Enrollment (Estimated): 75
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • Massachusetts
    • Boston, Massachusetts, United States, 02114
      • Massachusetts General Hospital, Department of Orthopaedics

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

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

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Blood Flow Restriction Resistance Training + Standard Physical Therapy; Participants receive standard postoperative Achilles tendon rehabilitation combined with blood flow restriction resistance training using the Delfi Personalized Tourniquet System. Cuffs are calibrated to 80% limb occlusion pressure to induce controlled vascular restriction during low-load resistance exercises. All sessions are supervised by trained physiotherapists following the standardized Massachusetts General Hospital Achilles rehabilitation protocol.	Device: Blood Flow Restriction Resistance Training (BFR-RT); Blood flow restriction resistance training will be performed using the Delfi Personalized Tourniquet System applied to the affected limb during supervised rehabilitation exercises. The device automatically determines limb occlusion pressure (LOP) and applies 80% of LOP during low-load resistance exercises. This controlled vascular restriction produces metabolic stress intended to stimulate muscle hypertrophy and strength recovery while minimizing mechanical load on the healing Achilles tendon. Sessions are conducted under physiotherapist supervision within the standardized postoperative rehabilitation protocol.; Other Names: Delfi Personalized Tourniquet System; Behavioral: Standard Physical Therapy; Participants will undergo the standardized postoperative Achilles tendon rehabilitation program used at Massachusetts General Hospital. The protocol includes progressive weight-bearing, range-of-motion exercises, strengthening maneuvers, and return-to-sport progression phases supervised by trained physiotherapists.; Other Names: Standard Postoperative Achilles Rehabilitation Protocol
Sham Comparator: Sham Blood Flow Restriction + Standard Physical Therapy; Participants receive the same standardized postoperative rehabilitation protocol while wearing Delfi tourniquet cuffs inflated to 20 mmHg, a pressure insufficient to induce blood flow restriction. This sham condition controls for potential placebo effects associated with the device while maintaining identical exercise protocols and therapist supervision.	Behavioral: Standard Physical Therapy; Participants will undergo the standardized postoperative Achilles tendon rehabilitation program used at Massachusetts General Hospital. The protocol includes progressive weight-bearing, range-of-motion exercises, strengthening maneuvers, and return-to-sport progression phases supervised by trained physiotherapists.; Other Names: Standard Postoperative Achilles Rehabilitation Protocol; Device: Sham Blood Flow Restriction; Participants assigned to the sham group will wear the Delfi tourniquet cuff during rehabilitation sessions; however, cuff pressure will be inflated only to 20 mmHg, a level insufficient to induce vascular occlusion. This condition mimics the experience of the intervention device while avoiding physiologic blood flow restriction, thereby controlling for potential placebo effects associated with device use.
Active Comparator: Standard Physical Therapy Alone; Participants undergo the standardized Massachusetts General Hospital postoperative Achilles tendon rehabilitation program including range-of-motion exercises, progressive strengthening, and return-to-sport phases. No blood flow restriction device is used during rehabilitation sessions.	Behavioral: Standard Physical Therapy; Participants will undergo the standardized postoperative Achilles tendon rehabilitation program used at Massachusetts General Hospital. The protocol includes progressive weight-bearing, range-of-motion exercises, strengthening maneuvers, and return-to-sport progression phases supervised by trained physiotherapists.; Other Names: Standard Postoperative Achilles Rehabilitation Protocol

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Achilles Tendon Total Rupture Score (ATRS)	The Achilles Tendon Total Rupture Score (ATRS) is a validated patient-reported outcome instrument used to assess symptoms and physical function following Achilles tendon rupture. The score ranges from 0 to 100, with higher scores indicating better function and fewer symptoms.	12 months postoperatively

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Ankle Plantarflexion Isometric Strength (Limb Symmetry Index)	Isometric ankle plantarflexion strength will be measured using the Fysiometer platform. Results will be expressed as limb symmetry index (LSI), calculated as the ratio of injured limb strength to contralateral limb strength expressed as a percentage.	3 months, 4.5 months, 6 months, and 12 months postoperatively
Gastrocsoleus Muscle Cross-Sectional Area	Cross-sectional area of the gastrocnemius-soleus muscle complex measured using portable ultrasound imaging to quantify muscle morphology and recovery following Achilles tendon repair.	6 weeks, 3 months, 4.5 months, 6 months, and 12 months postoperatively
Single-Leg Heel Rise Test	Functional calf endurance will be evaluated using the single-leg heel rise test measuring the number of heel raises completed on the affected limb.	3 months, 4.5 months, 6 months, and 12 months postoperatively
Single-Leg Heel Rise Height	Heel rise height will be measured during the single-leg heel rise test to assess plantarflexion strength and functional calf performance.	3 months, 4.5 months, 6 months, and 12 months postoperatively
International Physical Activity Questionnaire - Short Form (IPAQ-SF)	Physical activity levels will be assessed using the International Physical Activity Questionnaire - Short Form (IPAQ-SF), which evaluates participant activity levels across multiple domains.	6 months and 12 months postoperatively
Ankle Range of Motion	Active and passive ankle plantarflexion and dorsiflexion range of motion will be measured bilaterally using a goniometer.	6 weeks, 3 months, 4.5 months, 6 months, and 12 months postoperatively
Calf Circumference	Bilateral calf circumference measurements will be obtained to assess muscle atrophy and recovery following Achilles tendon repair.	6 weeks, 3 months, 4.5 months, 6 months, and 12 months postoperatively
Visual Analog Scale (VAS) Pain Score	Pain intensity will be measured using a 10-point Visual Analog Scale (VAS), where 0 represents no pain and 10 represents the worst possible pain. Higher scores indicate greater pain severity.	6 weeks, 3 months, 4.5 months, 6 months, and 12 months postoperatively
Patient-Reported Outcomes Measurement Information System (PROMIS) Pain Interference Score	Pain interference will be measured using the Patient-Reported Outcomes Measurement Information System (PROMIS) Pain Interference questionnaire. Scores are reported as T-scores with a mean of 50 and standard deviation of 10 in the general population; scores range from approximately 41 to 77, with higher scores indicating greater pain interference with daily activities.	6 weeks, 3 months, 4.5 months, 6 months, and 12 months postoperatively
Patient-Reported Outcomes Measurement Information System (PROMIS) Physical Function Score	Physical function will be assessed using the Patient-Reported Outcomes Measurement Information System (PROMIS) Physical Function questionnaire, which evaluates the participant's ability to perform physical activities. Scores are reported as T-scores with a mean of 50 and standard deviation of 10 in the general population; higher scores indicate better physical function.	6 weeks, 3 months, 4.5 months, 6 months, and 12 months postoperatively
Foot and Ankle Ability Measure (FAAM)	The Foot and Ankle Ability Measure (FAAM) is a validated patient-reported outcome instrument assessing functional limitations related to foot and ankle conditions. Scores range from 0 to 100, with higher scores indicating greater functional ability.	6 weeks, 3 months, 4.5 months, 6 months, and 12 months postoperatively
EQ-5D-5L Quality of Life Score	Health-related quality of life will be assessed using the EQ-5D-5L (EuroQol 5-Dimension 5-Level) questionnaire. The EQ-5D-5L index score ranges from 0 to 1, with higher scores indicating better health-related quality of life. A visual analogue scale (VAS) component ranges from 0 to 100, with higher scores indicating better self-rated health.	6 months and 12 months postoperatively

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Return-to-Sport Status and Time	Participants will report return-to-sport status and time required to resume pre-injury sport or physical activity.	Up to 12 months postoperatively

Collaborators and Investigators

• Sponsor: Massachusetts General Hospital

Publications and helpful links

General Publications

• Hughes L, Paton B, Rosenblatt B, Gissane C, Patterson SD. Blood flow restriction training in clinical musculoskeletal rehabilitation: a systematic review and meta-analysis. Br J Sports Med. 2017 Jul;51(13):1003-1011. doi: 10.1136/bjsports-2016-097071. Epub 2017 Mar 4.
• Heikkinen J, Lantto I, Piilonen J, Flinkkila T, Ohtonen P, Siira P, Laine V, Niinimaki J, Pajala A, Leppilahti J. Tendon Length, Calf Muscle Atrophy, and Strength Deficit After Acute Achilles Tendon Rupture: Long-Term Follow-up of Patients in a Previous Study. J Bone Joint Surg Am. 2017 Sep 20;99(18):1509-1515. doi: 10.2106/JBJS.16.01491.
• Centner C, Lauber B, Seynnes OR, Jerger S, Sohnius T, Gollhofer A, Konig D. Low-load blood flow restriction training induces similar morphological and mechanical Achilles tendon adaptations compared with high-load resistance training. J Appl Physiol (1985). 2019 Dec 1;127(6):1660-1667. doi: 10.1152/japplphysiol.00602.2019. Epub 2019 Nov 14.
• Hwang PS, Willoughby DS. Mechanisms Behind Blood Flow-Restricted Training and its Effect Toward Muscle Growth. J Strength Cond Res. 2019 Jul;33 Suppl 1:S167-S179. doi: 10.1519/JSC.0000000000002384.
• Hughes L, Rosenblatt B, Haddad F, Gissane C, McCarthy D, Clarke T, Ferris G, Dawes J, Paton B, Patterson SD. Comparing the Effectiveness of Blood Flow Restriction and Traditional Heavy Load Resistance Training in the Post-Surgery Rehabilitation of Anterior Cruciate Ligament Reconstruction Patients: A UK National Health Service Randomised Controlled Trial. Sports Med. 2019 Nov;49(11):1787-1805. doi: 10.1007/s40279-019-01137-2.
• Callanan MC, Plummer HA, Chapman GL, Opitz TJ, Rendos NK, Anz AW. Blood Flow Restriction Training Using the Delfi System Is Associated With a Cellular Systemic Response. Arthrosc Sports Med Rehabil. 2020 Dec 27;3(1):e189-e198. doi: 10.1016/j.asmr.2020.09.009. eCollection 2021 Feb.
• O'Neill S, Weeks A, Norgaard JE, Jorgensen MG. Validity and intrarater reliability of a novel device for assessing Plantar flexor strength. PLoS One. 2023 Mar 31;18(3):e0282395. doi: 10.1371/journal.pone.0282395. eCollection 2023.
• Rolnick N, Licameli N, Moghaddam M, Marquette L, Walter J, Fedorko B, Werner T. Autoregulated and Non-Autoregulated Blood Flow Restriction on Acute Arterial Stiffness. Int J Sports Med. 2024 Jan;45(1):23-32. doi: 10.1055/a-2152-0015. Epub 2023 Aug 10.
• Centner C, Jerger S, Lauber B, Seynnes O, Friedrich T, Lolli D, Gollhofer A, Konig D. Similar patterns of tendon regional hypertrophy after low-load blood flow restriction and high-load resistance training. Scand J Med Sci Sports. 2023 Jun;33(6):848-856. doi: 10.1111/sms.14321. Epub 2023 Feb 3.
• Eliasson P, Agergaard AS, Couppe C, Svensson R, Hoeffner R, Warming S, Warming N, Holm C, Jensen MH, Krogsgaard M, Kjaer M, Magnusson SP. The Ruptured Achilles Tendon Elongates for 6 Months After Surgical Repair Regardless of Early or Late Weightbearing in Combination With Ankle Mobilization: A Randomized Clinical Trial. Am J Sports Med. 2018 Aug;46(10):2492-2502. doi: 10.1177/0363546518781826. Epub 2018 Jul 2.
• Mashimo S, Nozaki T, Amaha K, Tanaka K, Kubota J, Sato H, Kitamura N. Quantitative Assessment of Calf Muscle Volume, Strength, and Quality After Achilles Tendon Rupture Repair: A 1-Year Prospective Follow-up Study. Am J Sports Med. 2023 Dec;51(14):3781-3789. doi: 10.1177/03635465231206391. Epub 2023 Nov 13.

Study record dates

Study Major Dates

• Study Start (Actual): February 1, 2026
• Primary Completion (Estimated): December 31, 2026
• Study Completion (Estimated): February 1, 2027

Study Registration Dates

• First Submitted: March 23, 2026
• First Submitted That Met QC Criteria: March 23, 2026
• First Posted (Actual): March 27, 2026

Study Record Updates

• Last Update Posted (Actual): April 1, 2026
• Last Update Submitted That Met QC Criteria: March 26, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Keywords: Tendon Injuries; Achilles Tendon; Blood Flow Restriction Training; Achilles Rehabilitation; Postoperative Physical Therapy; Hypoxic Muscle Recovery
• Additional Relevant MeSH Terms: Wounds and Injuries; Tendon Injuries
• Other Study ID Numbers: IRB#2026P000071

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: 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.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: Yes
• product manufactured in and exported from the U.S.: No