Background Lateral epicondylalgia is the most common cause of lateral elbow pain and affects approximately 1% to 3% of the population. It reduces strength, functionality, and quality of life, leading to limitations in work and daily activities and representing a relevant public health concern.

Current scientific evidence suggests conservative physical therapy as the first-line treatment; however, heterogeneity exists among approaches, and clinical guidelines remain unclear. Rest and pharmacological treatment may provide short-term relief but do not resolve the underlying condition and may lead to recurrences.

Therapeutic exercise has been shown to improve pain, strength, and function and is recommended as a first-line conservative intervention due to its favorable cost-benefit ratio. Thermotherapy and electrotherapy may also reduce pain and improve function compared with placebo.

This study aims to evaluate the efficacy of the Super Inductive System (SIS) combined with a conventional physical therapy program.

Hypothesis SIS therapy, combined with an upper extremity therapeutic exercise program and health education, will reduce pain, improve mobility and limb function, increase grip strength, facilitate return to activities of daily living (ADLs), and enhance perceived quality of life in individuals with lateral elbow tendinopathy.

Objective To assess the effectiveness of SIS combined with therapeutic exercise and health education in adults aged 18 years and older with lateral elbow tendinopathy, compared with the application of SIS at a non therapeutic dose combined with conventional therapeutic exercise and health education.

Methodology A prospective, experimental, randomized clinical trial will be conducted using a triple blind design (principal investigator, assessor, and participant). The study will include an intervention group (IG) (SIS at a therapeutic dose plus therapeutic exercise and health education) and a control group (CG) (SIS at a non therapeutic dose plus therapeutic exercise and health education).

This multicenter study will take place at three Rehabilitation and Physical Therapy Services (Mataró, Sant Andreu-Barcelona, and Drassanes-Barcelona), all part of the Primary Care network of the Catalan Health Institute (ICS).

Data collection will occur at baseline, post treatment, and at 3 and 6 month follow ups.

Outcome measures will assess pain using the Visual Analog Scale (VAS) and algometry, mobility through goniometric evaluation, upper limb function using the Quick Disabilities of the Arm, Shoulder and Hand questionnaire (QuickDASH), grip strength with dynamometry, health related quality of life with the EQ 5D 5L, and elbow specific pain and functional status using the Patient-Rated Tennis Elbow Evaluation (PRTEE).

Inferential analyses will be performed for within group and between group comparisons. Data will be processed in accordance with current legislation.

Data management will be performed using REDCap (Research Electronic Data Capture).

Expected Outcomes A statistically significant improvement is expected in the intervention group compared with the control group. The use of SIS may contribute to reduced recovery time, fewer and shorter temporary work disabilities, and lower pharmaceutical costs among individuals with lateral epicondylalgia.

Applicability and Relevance SIS is an innovative non invasive therapeutic technology that reduces acute and chronic pain, improves joint mobility, and promotes muscle strengthening in tendinopathies. Demonstrating its effectiveness and cost efficiency may support its incorporation into routine clinical practice, potentially reducing treatment duration, recovery time, and reliance on pharmacological therapy.

This study will provide evidence to inform the implementation of SIS as an additional therapeutic tool in primary care physical therapy and rehabilitation settings.

Background Lateral elbow tendinopathy, commonly referred to as lateral epicondylalgia or "tennis elbow," is the most frequent cause of lateral elbow pain in adults and represents a major musculoskeletal complaint in Primary Care. It is estimated to affect 1-3% of the population annually, with a peak incidence between 40 and 59 years. This condition is characterized by degenerative changes of the extensor carpi radialis brevis and, less frequently, the common extensor tendon. Clinically, individuals typically present with lateral epicondylar pain, decreased grip strength, functional impairment, and reduced quality of life, often affecting work performance and daily activities.

Diagnosis is mainly clinical, based on pain reproduction during resisted wrist extension or gripping tasks, and through positive provocative maneuvers such as Cozen's and Mill's tests. Additional assessments include pain intensity scales (VAS, NRS), pressure pain threshold via algometry, and grip strength using a JAMAR dynamometer. Ultrasound imaging may supplement clinical evaluation in selected cases.

Conservative management is considered the first-line approach for lateral elbow tendinopathy. Structured therapeutic exercise, including eccentric, isometric, and progressive strengthening programs, has demonstrated consistent benefits in reducing pain and improving function, with a favorable cost-benefit ratio. Manual therapy techniques used in combination with exercise may enhance outcomes. Electrotherapy modalities such as Transcutaneous Electrical Nerve Stimulation (TENS), laser therapy, iontophoresis, shortwave diathermy, and pulsed electromagnetic fields (PEMF) have shown varying degrees of effectiveness; however, heterogeneity in treatment protocols and evidence quality limits generalizability. Adjunctive treatments, such as orthoses, kinesiotape, and cryotherapy, may provide temporary symptom relief. More invasive options, such as corticosteroid injections, platelet-rich plasma, or surgery, are typically reserved for refractory cases and may be associated with adverse effects or limited long-term benefit.

The Super Inductive System (SIS) is a high-intensity pulsed electromagnetic fields (PEMF) technology capable of generating electromagnetic fields of up to approximately 2.5 Tesla. The device induces deep neuromuscular stimulation, producing muscle contractions and neuromodulatory effects that may reduce pain, improve joint mobility, and promote strengthening. Preliminary evidence, primarily from small-sample pilot studies and case series, suggests that SIS may generate immediate and short-term pain reduction and possibly contribute to tendon microstructural recovery. Despite promising findings, robust clinical trials evaluating SIS in lateral elbow tendinopathy are scarce, highlighting the need for higher-quality evidence.

Rationale Given the prevalence, functional impact, and healthcare burden associated with lateral elbow tendinopathy, it is essential to evaluate interventions capable of improving patient outcomes and reducing clinical, occupational, and pharmacological costs. In Primary Care settings, where most cases are managed, optimized conservative approaches are particularly relevant. While therapeutic exercise and education remain the cornerstone of treatment, incorporating SIS may provide additional benefits, including enhanced pain reduction, improved muscle activation, and accelerated functional recovery.

There is an important evidence gap regarding the integration of SIS into multimodal rehabilitation programs for lateral elbow tendinopathy. Current literature is limited by small sample sizes, methodological variability, and short follow-up durations. This trial addresses a relevant clinical question: whether adding SIS at a therapeutic dose to a standardized exercise and education protocol provides superior outcomes compared with an active placebo SIS dose combined with the same conservative care.

Hypothesis The study hypothesizes that the application of therapeutic dose Super Inductive System (SIS) therapy, when combined with an upper extremity therapeutic exercise program and health education, will result in greater clinical improvement than a non therapeutic SIS dose combined with the same exercise and education protocol. Specifically, it is expected that participants receiving therapeutic dose SIS will exhibit a more pronounced reduction in pain intensity, greater improvements in elbow mobility and upper limb function, increased grip strength, enhanced performance of daily activities, and better health related quality of life throughout the intervention and follow up periods.

Objectives

Primary Objective:

To evaluate the effectiveness of therapeutic-dose SIS combined with therapeutic exercise and health education in adults aged 18 years or older with lateral elbow tendinopathy, compared with a non-therapeutic SIS dose plus exercise and education.

Secondary Objectives:

• Quantify changes in pain using VAS and algometry.
• Assess changes in active elbow mobility using a goniometer.
• Evaluate functional improvement using the QuickDASH.
• Determine changes in grip strength measured with a JAMAR dynamometer.
• Analyze health-related quality of life using the EQ 5D 5L.
• Evaluate elbow-specific pain and disability using the PRTEE.
• Document adherence to exercise and treatment attendance.
• Register adverse events associated with the interventions.
• Compare medication use before and after treatment.
• Assess temporary work disability (frequency and duration).
• Compare baseline clinical and sociodemographic characteristics between groups.

Study Design This study is a multicenter, randomized, prospective, experimental clinical trial with a triple-blind structure. Participants, the principal investigator, and the outcome assessors will remain blinded to group allocation. Due to the nature of the intervention, physical therapists administering SIS cannot be blinded, but they will not participate in outcome assessment or data analysis.

Randomization will be simple, using a computer-generated numerical sequence, with allocation concealed through opaque envelopes handled by administrative staff. The evaluator responsible for baseline and follow-up assessments will have no access to the allocation sequence. Participants will be informed that two active modalities of SIS are compared but will not be informed which dosing protocol they receive.

The trial will be conducted in three Primary Care Rehabilitation and Physical Therapy Services: Mataró (Barcelona), Sant Andreu (Barcelona), and Drassanes (Barcelona), all part of the Catalan Health Institute. Recruitment, intervention, and follow-up assessments will occur between 2026 and 2027, with final data analysis and dissemination extended through 2028. The sample size has been calculated based on detecting a ≥20% difference in primary outcomes with α = 0.05, statistical power >0.80, and accounting for 20% attrition, resulting in a target enrollment of 224 participants (112 per group).

Participating Centers

• Rehabilitation and Physical Therapy Service, Mataró-Barcelona
• Rehabilitation and Physical Therapy Service, Sant Andreu-Barcelona
• Rehabilitation and Physical Therapy Service, Drassanes-Barcelona These centers share comparable resources, equipment, and clinical pathways, ensuring protocol standardization and facilitating generalizability across Primary Care settings.

Scope and Study Period The intervention phase of the study is planned to begin in 2026, with participant recruitment, treatment delivery, and follow up assessments extending through the end of 2027. Final data verification, analysis, manuscript preparation, and dissemination activities are expected to continue into 2028. This timeline ensures adequate follow up for medium term outcomes and sufficient power to detect clinically meaningful changes.

Population, Eligibility, and Sampling Strategy The reference population comprises adults aged 18 years and older presenting with acute or chronic lateral elbow tendinopathy. Eligible individuals will be those referred to the participating rehabilitation services from Family Medicine, Rehabilitation, Orthopedics, or Rheumatology. The sampling strategy involves consecutive recruitment of all eligible and consenting individuals until the required sample size is achieved.

Sample size calculations were based on detecting a minimum clinically important difference of at least 20% in the primary outcome variables, using a two sided significance level of 0.05 and statistical power above 0.80. The resulting target sample size is 186 participants (93 per group), increased to 224 participants in total to account for an estimated 20% loss to follow up.

Recruitment and Randomization Procedures Recruitment will be performed through structured referral pathways within the Primary Care network. After a screening review by the service lead, eligible individuals will be contacted by administrative staff to schedule an initial evaluation with a dedicated assessor. During this visit, baseline data will be collected, inclusion/exclusion criteria will be verified, and informed consent (including optional image use) will be obtained.

Allocation will follow a simple randomization process using a numeric sequence generated electronically. Concealment will be ensured using opaque, sealed envelopes. After baseline assessment, the evaluator assigns the envelope to administrative staff, who then schedule participants and communicate the allocation only to the physical therapists responsible for treatment delivery. Throughout the study, blinding will be maintained for participants, the principal investigator, and all assessors involved in data collection.

Interventions Treatment Components Shared by Both Groups

Both the intervention and control groups will receive:

• a standardized therapeutic exercise program, with weekly progression based on pain, mobility, and strength findings, performed four days per week, consisting of 2 sets of 10 repetitions per exercise, supplemented with self massage of the affected musculature;
• a health education component including information on the pathology, ergonomics, preventive guidelines, and recommendations for daily activities.

Participants will receive written materials, visual illustrations, and QR codes linking to exercise videos to support adherence at home.

Intervention Group (IG): Therapeutic Dose SIS Participants in the IG will receive therapeutic dose SIS using the BTL 6000 Super Inductive System Elite, applying a predefined 10 minute protocol for elbow tendinopathies. The intensity will be adjusted according to participant tolerance to achieve motor level stimulation and neuromodulatory effects. SIS will be applied after exercise and education to capitalize on its expected analgesic and muscle activation effects.

Control Group (CG): Active Placebo SIS Participants in the CG will receive a non therapeutic SIS protocol (active placebo), using low intensity parameters (1 Hz, 59 second pause, 1% intensity) for 10 minutes, providing an experience that mimics treatment without delivering clinically meaningful stimulation.

Both groups will attend 2 sessions per week for a total of 8 sessions. Attendance and reasons for non attendance will be systematically documented to quantify adherence and absenteeism.

Outcome Measures and Assessment Tools All outcome measures were selected based on their clinical relevance, validity, and reliability in lateral elbow tendinopathy.

Primary Outcome:

• Pain intensity measured using the Visual Analog Scale (VAS) and pressure pain threshold assessed via algometry.

Secondary Outcomes:

• Elbow range of motion measured using a manual goniometer (flexion, extension, pronation, supination).
• Grip strength measured with a JAMAR hydraulic dynamometer (three maximal trials with standardized positioning).
• Upper limb function assessed using the QuickDASH.
• Health related quality of life measured via the EQ 5D 5L.
• Elbow specific pain and disability measured using the PRTEE.
• Exercise adherence recorded through participant logs.
• Adverse events monitored using a standardized questionnaire.
• Medication consumption related to pain management (pre/post comparison).
• Temporary work disability, including number and duration of episodes.
• Session attendance and percentage of absenteeism.

Measurement Schedule

All participants will undergo assessments at four timepoints:

1. Baseline (pre intervention)
2. End of treatment (after 8 sessions)
3. Three month follow up
4. Six month follow up This schedule enables evaluation of both immediate therapeutic effects and medium term outcomes related to functional recovery and symptom recurrence.

Procedures, Operational Flow, and Organization

The study will follow a coordinated workflow involving clinical, administrative, and research personnel to ensure fidelity to the protocol and standardization across the three centers. Key organizational elements include:

• Internal team training involving the principal investigator, evaluators, and physical therapists to ensure understanding of study procedures, documentation, and treatment protocols.
• Baseline assessment visits lasting approximately 45 minutes, where evaluators conduct clinical examination, administer instruments, and manage informed consent.
• Secure management of randomization envelopes and coordination between evaluators, administrative staff, and physical therapists to maintain blinding.
• Systematic recording of follow up assessments and adherence using REDCap and the ICS clinical information system (eCAP).
• Regular monitoring of sessions, dropouts, and adverse effects by the research team.

Sociodemographic and Clinical Variables In addition to the primary and secondary outcomes, the study will collect relevant sociodemographic and clinical variables, including age, sex, educational level, marital status, living situation, employment status, dominant hand, affected limb, medical history, duration of symptoms, referring clinician, diagnostic tests performed, use of orthoses, sports participation, temporary disability status and dates, and pre and post treatment pharmacological management.

Data Management and Storage Study data will be collected and managed using REDCap, with secure access, audit trails, and version control. Data will also be stored on institutionally approved encrypted servers (Office 365 ICS cloud), with strictly controlled access limited to investigators. Each participant will be assigned a randomly generated study code with no direct link to identifiable clinical information in the main dataset. The key linking these codes to personal identifiers will be stored separately in an encrypted and password protected file accessible only to the principal investigators.

Data retention will comply with institutional and legal requirements, with all study data preserved for five years following project completion. No international data transfers are planned, and no data will be shared with third parties unless legally required or authorized by participants.

Ethical Considerations The study adheres to the ethical guidelines established by the Declaration of Helsinki (Fortaleza amendment), Good Clinical Practice standards, the European Union General Data Protection Regulation (GDPR), and Spanish data protection regulations (LOPDGDD). Ethical approval will be sought from the IDIAP Jordi Gol Ethics Committee before initiating recruitment.

Participants will be informed of the study objectives, potential benefits and risks, confidentiality safeguards, data protection measures, and their right to withdraw at any time without prejudice. Consent procedures include optional authorization for image use where applicable.

Safety and Adverse Events Monitoring All adverse events potentially related to SIS or the therapeutic exercise program will be systematically recorded using a standardized form. In cases of intense or persistent discomfort, treatment may be paused or modified as clinically appropriate. Adverse events will be compared between the intervention and control groups using descriptive statistics.

Statistical Analysis Plan

The statistical analysis will include:

• Descriptive statistics (means, SD, medians, IQR, frequencies, percentages).
• Tests of normality (Shapiro-Wilk or Kolmogorov-Smirnov depending on sample size).
• Baseline group comparisons using Student's t test or Mann-Whitney U test for continuous variables and chi square tests for categorical variables.
• Within group pre post changes assessed via paired t tests or Wilcoxon signed rank tests.
• Analysis of changes across all timepoints (baseline, final, 3 and 6 months) using repeated measures ANOVA or Friedman tests, with Bonferroni adjustments for multiple comparisons.
• Multivariate modeling incorporating variables with p < 0.25 in univariate analyses or those considered clinically relevant, assessing confounding, interactions, and collinearity.
• Statistical significance set at α = 0.05.

Anticipated Challenges and Limitations Potential limitations include loss to follow up due to absenteeism, health changes, or participant motivation. The protocol accounts for this through oversampling and systematic follow up reminders. Variability in adherence to home exercises will be mitigated through clear written instructions, video resources, and monitoring logs. The study attempts to control for concurrent treatments through careful documentation and consideration during analysis.

Expected Impact, Utility, and Applicability Integrating therapeutic dose SIS into a multimodal rehabilitation program is expected to enhance recovery by reducing pain more effectively, improving mobility and function, strengthening grip, and improving quality of life. Additionally, improvements may translate into reduced medication use, fewer temporary work disability days, and decreased healthcare utilization. Findings will provide robust evidence regarding the safety and effectiveness of SIS in Primary Care and may support its adoption into routine rehabilitation practice.

Inclusion Criteria:

• Adults aged 18 years or older.
• Clinical diagnosis of lateral elbow tendinopathy confirmed by a Family Care Physician, Rehabilitation Physiatrist, Orthopedic Surgeon, or Rheumatologist.
• Referral to one of the three participating Rehabilitation and Physical Therapy Services (Mataró, Sant Andreu, or Drassanes).
• Presence of at least one positive provocative test (Cozen's test or Mill's test).
• Ability and willingness to participate in the study after reading the patient information sheet and signing the informed consent, including consent for image use.

Exclusion Criteria:

• Medial elbow tendinopathy.
• Recent traumatic injury to the affected upper limb within the past 6 months.
• Passive elbow joint range of motion limited by more than 20°.
• Injection in the affected elbow within 6 weeks prior to baseline assessment.
• Systemic inflammatory, autoimmune, infectious, or neoplastic disease.
• Pregnancy.
• Metal implants in the affected elbow region.
• Pacemaker or implantable defibrillator.
• Radial tunnel syndrome / Frohse arcade syndrome.
• Coagulation disorders.
• Cognitive or sensory impairment that precludes participation in the study procedures.
• Central sensitization syndromes (e.g., fibromyalgia, chronic fatigue syndrome).

Individual Participant Data (IPD) from this study will be available to qualified researchers upon reasonable request. Data will be shared in a de-identified format to protect participant confidentiality and will be provided through secure transfer procedures. Access will be granted to investigators who submit a methodologically sound proposal and a clear scientific rationale. Requests may be directed to the Principal Investigator and will be evaluated on a case-by-case basis in accordance with ethical and regulatory requirements.

IPD and supporting documents will be available starting in January 2027 and will remain available with no planned end date.

Access to IPD and supporting documentation will be granted to qualified researchers who request the data for legitimate scientific purposes and submit a proposal with a sound methodological approach and ethical rationale. Data will be provided in a fully de-identified format, along with relevant supporting documents when appropriate, and will be shared through secure transfer procedures to ensure participant confidentiality. Requests should be submitted to the Principal Investigator and will be evaluated on a case-by-case basis in accordance with applicable ethical and legal regulations. Data use will not be permitted for any purpose that could compromise participant privacy or well-being.

Participants, the principal investigator, and the outcomes assessors are blinded to group allocation. Randomization is managed through opaque sequentially numbered envelopes. Only the physical therapists delivering the interventions have access to the randomization sequence.