This randomized controlled trial aims to compare the effectiveness of eccentric training combined with blood flow restriction (ECC+BFR) versus heavy slow resistance (HSR) training in patients with chronic lateral epicondylitis. The study will recruit 40 participants (accounting for 10% attrition), aged 25-45 years, from Sakina Memorial Hospital Sheikhupura and University of Lahore Teaching Hospital using convenience sampling. Participants will be randomly allocated into two groups: an interventional group receiving ECC+BFR and a control group undergoing HSR training. Both interventions will be administered three times per week for 8 weeks under professional supervision. Outcome measures including pain intensity (NPRS), patient-specific functional performance (PSFS), muscle strength, and hypertrophy will be assessed at baseline, 4 weeks, and 8 weeks. Data will be analyzed using SPSS, with appropriate parametric or non-parametric tests applied after checking data normality. Ethical approval will be obtained, informed consent will be secured, and participant confidentiality will be strictly maintained.

This study is a single-blinded randomized controlled trial designed to evaluate and compare the therapeutic effectiveness of eccentric training with blood flow restriction (ECC+BFR) and heavy slow resistance (HSR) training in individuals diagnosed with chronic unilateral lateral epicondylitis. The study will be conducted at Sakina Memorial Hospital Sheikhupura and University of Lahore Teaching Hospital over a duration of 9 months following synopsis approval.

A total sample size of 40 participants (20 per group) has been determined using Epitool software, based on the Patient-Specific Functional Scale (PSFS), with a confidence level of 95%, power of 80%, and a 10% attrition allowance. Participants aged 25-45 years, of both genders, with clinically confirmed chronic lateral epicondylitis (positive Cozen's and Mill's tests) and symptom duration exceeding 12 months, will be included. Individuals with prior surgery, recent injections, systemic inflammatory conditions, vascular or clotting disorders, contraindications to BFR, pregnancy, or psychological illness will be excluded.

Eligible participants will be enrolled after providing written informed consent and randomized using a computer-generated block randomization method, with allocation concealment ensured through sealed opaque envelopes. Outcome assessors will be blinded to group allocation to minimize assessment bias.

The interventional group will receive eccentric wrist extensor exercises combined with blood flow restriction therapy, using a pneumatic cuff inflated to 50-60% limb occlusion pressure. Exercises will be performed at 20-30% 1-RM using a 30-15-15-15 repetition protocol, emphasizing slow controlled eccentric contractions. Sessions will be conducted three times weekly for 8 weeks, totaling 24 supervised sessions.

The control group will undergo a heavy slow resistance training protocol, involving wrist extensor exercises performed at 70-85% of 1-RM, with slow concentric and eccentric phases (3 seconds each). Participants will complete 3-4 sets of 6-8 repetitions, with adequate rest intervals, following the same session frequency and duration as the intervention group.

Primary and secondary outcome measures include pain intensity (Numeric Pain Rating Scale), patient-specific functional performance (PSFS), muscle strength, and muscle hypertrophy, assessed at baseline, 4 weeks, and 8 weeks post-intervention. Data will be analyzed using SPSS (version 25/27). Descriptive statistics will summarize participant characteristics, while inferential statistics will be applied based on data distribution, with significance determined accordingly.

Ethical considerations will strictly adhere to the guidelines of the Institutional Research Ethics Board (IREB), University of Lahore. Participant confidentiality, voluntary participation, right to withdraw, and safety monitoring will be ensured throughout the study. No serious adverse effects are anticipated.

Inclusion Criteria:

Patient aged between 25 and 45 years. Both male and female participants with unilateral symptoms only. Clinically diagnosed unilateral lateral epicondylitis (LE), confirmed by positive Cozen's and Mills' tests. Symptom duration exceeding 12 months, indicating chronic LE.

Exclusion Criteria:

Previous history of surgery or injection therapy for LE within the past 6 months.

Coexisting conditions (e.g., rheumatoid arthritis, cervical radiculopathy, significant tendon tears). Contraindications to BFR (e.g., DVT, vascular disease, uncontrolled hypertension, clotting disorders).

Use of anticoagulants or long-term pain medications. Pregnant or psychological person.