Chronic insertional Achilles tendinopathy is a common overuse condition that can be slow to improve with traditional loading-based rehab (e.g., eccentric loading, activity modification, graded return to function). Outcomes are often variable, and persistent symptoms can limit how much load patients can tolerate early in rehab.

This outpatient randomized controlled trial will compare standard-of-care rehabilitation alone versus standard-of-care rehabilitation plus blood flow restriction (BFR) training in adults with chronic insertional Achilles tendinopathy. BFR uses an external cuff to partially restrict blood flow during low-load resistance exercise, aiming to produce strength and hypertrophy adaptations with less mechanical stress than high-load training. Evidence supporting BFR's physiologic effects and safety in musculoskeletal rehab is summarized in clinical research literature.

Participants will be randomized (stratified by baseline activity level and symptom severity) to receive the same rehab program, with the experimental group performing strengthening with BFR using Smart Tools Plus cuffs applied at the proximal thigh and set to 40-80% limb occlusion pressure. The primary outcome will be the VISA-A score (a validated measure of Achilles tendinopathy severity), with secondary outcomes including pain ratings, functional performance tests (e.g., single-leg heel raise endurance, hopping/time-to fatigue), and calf strength via handheld dynamometry.

Chronic insertional Achilles tendinopathy is an overuse condition with prolonged recovery, where outcomes after traditional loading programs can be variable. Your protocol builds on standard rehabilitation principles (progressive loading, symptom-guided activity modification, and graded return to function) while testing whether blood flow restriction (BFR) can improve rehabilitation efficiency by enabling meaningful neuromuscular adaptation at lower external loads. This rationale aligns with emerging mechanistic and clinical evidence that low-load BFR can drive clinically relevant adaptations while reducing mechanical stress on painful tissues.

This study is designed as a two-arm randomized controlled trial conducted in an outpatient rehabilitation setting, comparing standard-of-care rehabilitation alone versus standard-of-care rehabilitation augmented with BFR. The overarching hypothesis is that adding BFR to a structured rehabilitation pathway will yield superior improvements in pain-related disability and function (tracked with validated clinical instruments) and will translate into better performance on functional tasks commonly affected in Achilles tendinopathy (e.g., endurance and hopping tolerance).

To ensure diagnostic precision and a clinically homogeneous sample, the protocol specifies confirmation of chronic insertional Achilles tendinopathy using a combination of symptom chronicity and exam/imaging features, including localized tenderness near the calcaneal insertion, functional provocation testing, and imaging evidence of structural tendon change (ultrasound or MRI). These steps are intended to reduce misclassification and improve interpretability of treatment effects in a condition with multiple pain generators around the posterior heel.

Randomization is structured to enhance baseline balance on variables that can meaningfully influence rehabilitation response. Specifically, allocation is stratified by baseline activity level (Cincinnati Sports Activity Scale) and by baseline clinical severity using a VISA-A threshold (<50 vs ≥50). The target sample size is 40 participants (20 per group), selected to detect a clinically meaningful improvement on the VISA-A (minimal clinically important difference of 10 points) with 90% power and α=0.05, while incorporating an allowance for attrition. The analysis plan is aligned with CONSORT expectations for rehabilitation trials and anticipates covariate-adjusted mixed modeling to evaluate group-by-time effects.

Intervention delivery follows a pragmatic rehabilitation model. The standard-care arm uses established physical therapy approaches-progressive loading (including eccentric-focused strategies), education on activity modification, and a staged return-to-function progression-implemented and advanced based on symptoms and functional tolerance. In the BFR-augmented arm, the same rehabilitation exercises are performed while applying BFR using Smart Tools Plus (LLC, USA) with limb sleeves and cuffs placed proximally on the thigh. Limb occlusion pressure (LOP) is set individually immediately prior to exercise, and the protocol applies 40-80% of LOP during the exercise sets. Participants are monitored throughout for adverse signs/symptoms, consistent with published evidence that BFR-when appropriately screened, dosed, and supervised-has an acceptable safety profile in musculoskeletal rehabilitation populations.

Outcomes are captured longitudinally across baseline and follow-up timepoints and include a patient-reported measure of Achilles tendinopathy severity (VISA-A) and functional performance metrics (e.g., single-leg heel raise endurance, hopping tolerance/time to fatigue), alongside quantification of plantarflexor/calf strength using handheld dynamometry. The VISA-A is a widely used index with published reliability and construct validity for grading clinical severity in Achilles tendinopathy research.

Data will be evaluated using repeated-measures modeling to compare within-group change over time and between-group differences in trajectories, with covariate adjustment consistent with the stratification variables and planned mixed-model approach. Results will be reported at the group level and interpreted in relation to clinically meaningful change thresholds, with the goal of informing whether BFR is a practical and scalable adjunct to standard rehabilitation for chronic insertional Achilles tendinopathy-especially for patients who cannot tolerate higher external loads early in the rehabilitation process.

Inclusion Criteria:

• Age 18-65 years
• Chronic insertional Achilles tendinopathy (symptoms >3 months but <3 years)
• VISA-A score <80
• Confirmed diagnosis via:
• Palpation pain within 2 cm of calcaneal insertion
• Positive single leg-hop test
• Ultrasound or MRI evidence of structural tendon changes (hypoechoic areas, thickening, or Doppler flow)
• No prior BFR training as part of rehab within the last 3 months

Exclusion Criteria:

• Inability to give informed consent
• Uncontrolled blood pressure (>160/100 mmHg)
• Uncontrolled diabetes
• Familial hypercholesterolemia
• History of deep vein thrombosis
• History of blood clots
• Hypercoagulable states
• Cancer
• Active infection
• History of sickle cell anemia
• Peripheral vascular disease
• Morbid obesity (BMI >40)
• End-stage renal disease requiring dialysis
• Alcohol use disorder / alcohol abuse
• Claustrophobia
• Pregnant woman
• Inability to follow study protocol (e.g., cannot attend visits or comprehend instructions)
• Psychiatric illness preventing comprehension or interfering with follow up
• Lymphadenectomy
• Any clinical finding that places the patient at health risk, impacts the study, or affects completion
• History of Achilles tendon rupture or surgery
• Concurrent midportion Achilles tendinopathy or other ankle pathology (e.g., arthritis)
• Recent treatments within the past 3 months: physiotherapy, local injections, shockwave therapy, orthotic use