Effectiveness of Combined Super Inductive System (SIS) Therapy With Therapeutic Exercise and Health Education in Lateral Elbow Tendinopathy

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. *

• Pressure Pain Threshold measured by algometry [Time frame: Baseline, 4 weeks, 3 months, and 6 months after end of treatment. Unit of Measure: kg/cm²]
• Elbow range of motion measured with a goniometer [Time frame: Baseline, 4 weeks, 3 months, and 6 months after end of treatment. Unit of Measure: Degrees (°).]
• Grip strength measured with JAMAR dynamometer [Time frame: Baseline, 4 weeks, 3 months, and 6 months after end of treatment. Unit of Measure: Kilograms (kg).]
• Upper limb disability measured with the QuickDASH score [Time frame: Baseline, 4 weeks, 3 months, and 6 months after end of treatment. Unit of Measure: Score (0-100)]
• Health related quality of life measured with the EQ 5D 5L [Time frame: Baseline, 4 weeks, 3 months, and 6 months after end of treatment. Unit of Measure: Index score; VAS score (0-100)]
• Elbow specific pain and function measured with the PRTEE [Time frame: Baseline, 4 weeks, 3 months, and 6 months after end of treatment. Unit of Measure: Score (0-100).]