Aim of the Study

The aim of this study is to investigate the differential effects of high-intensity and low-intensity percutaneous electrolysis (PCE) on pain perception and muscle tissue properties in individuals with chronic plantar fasciitis.

Research Questions

Pain Perception:

Does high-intensity PCE induce greater changes in pressure pain threshold (PPT) in the plantar fascia compared to low-intensity PCE in individuals with chronic plantar fasciitis?

Muscle Tissue Properties:

Does high-intensity PCE reduce stiffness in the plantar fascia to a greater extent than low-intensity PCE in individuals with chronic plantar fasciitis?

A randomized, controlled, triple-blind clinical trial will be conducted to compare the effects of a single session of percutaneous intertissued electrolysis in three different modes (two intervention groups with the same dose but different intensity and time parameters, and one intervention group with a different dose) in patients with chronic plantar fasciitis (PF).

This study will be conducted under the Consolidated Standards of Reporting Trials (CONSORT) guidelines for pragmatic clinical trials and the EQUATOR guidelines to improve health research quality and transparency. Since the study involves patients with plantar pain, participants' rights will be respected under the Declaration of Helsinki. The Ethics Committee of University Hospital 12 de Octubre must approve the study protocol before data collection begins. The study protocol will also be prospectively registered on ClinicalTrials.org before data collection begins.

Sociodemographic variables (age, sex, weight, height, and body mass index), clinical variables (pain intensity, disability related to PF, pain thresholds to pressure), mechanical variables (plantar fascia stiffness), and tolerance to the treatment (visual analog scale to assess the intensity of pain felt during the intervention) will be assessed. Sociodemographic variables will be collected before the intervention, clinical and mechanical variables before and after the intervention, and tolerance to treatment only after the intervention. The assessment of participants will be carried out by an assessor who will not know which intervention group the participant belongs to. Participants will not know what dose they received, and the physiotherapists performing the procedures will also not know what settings the electrotherapy device has.

Participants will be randomly assigned to one of three intervention groups using a random number generator (Research Randomizer, version 4.0). Individual cards with numbers assigned sequentially according to the randomization will be used, which will then be folded and placed in opaque, sealed envelopes to ensure the concealment of allocation. An external researcher will select the envelope and make the assignment, which will only be revealed to the external therapist setting the equipment parameters after the initial data collection is completed. The assessor, therapist, and participants will not know to which group they have been assigned.

Inclusion Criteria:

• age 18 years or older,
• unilateral heel pain lasting longer than 3 months,
• a clinical diagnosis of chronic plantar fasciitis according to the clinical practice guidelines of the Orthopaedic Section of the American Physical Therapy Association (APTA), i.e., sudden onset of pain on the plantar surface of the heel after a period of non-weight bearing, pain that is worse in the morning with the first step, and tenderness to palpation at the proximal attachment site of the plantar fascia.

Exclusion Criteria:

• previous lower extremity surgery,
• the presence of positive neurological signs consistent with nerve root compression,
• any medical conditions causing heel pain, such as rheumatoid arthritis, diabetes, or peripheral neuropathy,
• receipt of any foot treatment within the past 6 weeks.