Peripheral Magnetic Stimulation of Foot Muscles: Effects on Medial Longitudinal Arch Height and Foot Muscle Strength in Adults With Flat Feet (rPMS-Foot)

May 30, 2026 updated by: Ales Dolenec, University of Ljubljana

Peripheral Magnetic Stimulation of Foot Muscles

This study examines the effects of repetitive peripheral magnetic stimulation (rPMS) on foot invertor muscle strength, morphology, and the height of the medial longitudinal arch (MLA) in individuals with flat feet. The rPMS will be applied non-invasively to the extrinsic and intrinsic foot muscles three times per week for twelve weeks. The experimental group will receive rPMS targeting the invertor muscles of the foot, while the control group will not receive stimulation but will follow the same measurement schedule.

Assessments will be performed at baseline, after 6 weeks, and after 12 weeks of intervention. The primary outcome will be the change in the height of the MLA, evaluated using dynamic navicular drop assessment during gait. Secondary outcomes will include changes in the isometric inversion torque of the foot invertors and morphological adaptations of the tibialis posterior muscle assessed by ultrasound imaging.

This study seeks to determine whether rPMS can improve the height of the MLA, foot invertor muscle strength and structural stability in adults with flat feet. The findings may contribute to developing new, non-invasive therapeutic approaches for improving foot function and preventing musculoskeletal imbalances related to flat foot deformity.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Detailed Description

During movement, the role of the foot muscles is often overlooked. Through their strength and stabilizing function, foot muscles play an important role in maintaining balance, posture, and force transmission throughout the body. Proper activation of these muscles also helps preserve the stability of the medial longitudinal arch (MLA), thereby influencing the overall biomechanics of human movement.

The foot muscles are classified as extrinsic (originating outside the foot) and intrinsic (originating and inserting within the foot). Extrinsic muscles, primarily stabilize the ankle joint and control larger movements, whereas intrinsic muscles store and release elastic energy within the foot, contributing to arch support and movement efficiency.

A lowered height or collapsed arch of the foot, known as flat foot (pes planus), is characterized by arch flattening during weight-bearing and affects approximately 13-27% of the adult population. This deformity alters force distribution and shock absorption, increasing mechanical load on the joints and muscles of the lower kinetic chain. Consequently, flat feet are often associated with foot pain, tendinopathies, and different musculoskeletal disorders in the knees, hips, and lumbar spine.

One of the main causes of flat foot deformity is dysfunction of the tibialis posterior (TP) tendon. This dysfunction leads to reduced muscle strength, decreased neuromuscular activation of the foot invertors and plantar flexors, and subsequent lowering of the navicular bone, resulting in a reduced MLA height. Strengthening the m. TP not only maintains arch position but also improves gait efficiency by reducing compensatory activation of other muscles. This muscle is considered as the strongest foot invertor and has the largest moment arm along the subtalar axis.

Recent research highlights that strengthening foot invertor muscles, particularly m. TP, can effectively increase height of the MLA. Conventional interventions include specific exercise programs and proprioceptive neuromuscular facilitation techniques. However, neuromuscular electrical stimulation used in previous studies did not showed significant increases in MLA height, partly due to pain and discomfort during deep muscle stimulation.

Repetitive peripheral magnetic stimulation (rPMS) has emerged as a promising non-invasively alternative, capable of stimulating deep neuromuscular structures. Several studies have shown that high-frequency rPMS can induce muscle activation, transient swelling, and potential hypertrophy indicators. Nevertheless, there is limited evidence on the long-term (multi-week) effects of rPMS on deep muscles such as the m. TP.

Aim of this research is to implement a 12-week rPMS protocol targeting both extrinsic and intrinsic foot invertor muscles, and to examine whether rPMS induces changes in the height of the MLA. Additionally, the study aims to determine whether 12-week rPMS protocol contributed to increased strength and cross-sectional area of the m. TP.

Study Type

Interventional

Enrollment (Estimated)

30

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Locations

  • Slovenia
    • Ljubljana
      • Ljubljana, Ljubljana, Slovenia, 1000
        • Not yet recruiting
        • Faculty of Sport, University of Ljubljana
      • Ljubljana, Ljubljana, Slovenia, 1000

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Age between 18 and 50 years,
  • functionally flat feet of participants.

Exclusion Criteria:

  • Acute leg injuries,
  • diabetes,
  • vascular disorders of the lower limbs,
  • open wounds or skin lesions on the lower leg or foot,
  • participants with metal implants near the stimulation site,
  • cardiac pacemaker,
  • other orthopedic or neurological conditions that could affect the study results or pose a health risk to the participants.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Single

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: rPMS Stimulation Group
Subjects in this group will receive repetitive peripheral magnetic stimulation (rPMS) of the foot invertor muscles three times per week for 12 weeks. Stimulation will be applied to the upper third of the anteromedial side of the shin. Intrinsic foot muscles will be simultaneously stimulated using a foot stimulator, with the nondominant foot placed on the stimulation platform. Participants in the experimental group will complete ultrasound imaging, navicular drop assessment, clinical evaluation of the plantar arch index, and isometric strength testing of the foot invertor muscles at three time points: before the intervention (baseline), after 6 weeks, and after 12-week stimulation period.
Device: Repetitive Peripheral Magnetic Stimulation (rPMS)
Repetitive peripheral magnetic stimulation (rPMS) will be applied to the foot invertor muscles three times per week for 12 weeks. Stimulation will target the upper third of the anteromedial side of the shin, near the tibia, using an oval magnetic coil. To ensure correct coil placement, visible muscle contraction and ankle inversion will be monitored. Intrinsic foot muscles will be simultaneously stimulated using a foot stimulator, with the nondominant foot positioned on the stimulation platform. Participants will perform isometric inversion contractions during rPMS to enhance neuromuscular activation and short-foot exercises to engage local foot stabilizers.
Other Names:
  • FMS
  • rPMS
  • Peripheral Magnetic Stimulation
  • Functional Magnetic Stimulation
No Intervention: Control Group (no stimulation)
Subjects in control group will not receive any stimulation but will undergo the same measurement procedures as the experimental group, including ultrasound imaging, navicular drop assessment, clinical evaluation of the plantar arch index, and isometric strength testing of the foot invertor muscles before and after the 6- and 12-week period.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Change in medial longitudinal arch height
Time Frame: Baseline (Day 1), Week 6, Week 12
Measuring dynamic navicular drop assessment during the stance phase of gait.
Baseline (Day 1), Week 6, Week 12

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Change in isometric inversion torque of the stimulated foot
Time Frame: Baseline (Day 1), Week 6, Week 12
Measured using an special designed isometric device to assess maximal voluntary torque during foot inversion in subtalar exis.
Baseline (Day 1), Week 6, Week 12

Other Outcome Measures

Outcome Measure
Measure Description
Time Frame
Change in cross-sectional area of the tibialis posterior muscle
Time Frame: Baseline (Day 1), Week 6, Week 12
Measured using ultrasound imaging to evaluate morphological adaptations of the tibialis posterior muscle and/or other foot invertor muscles.
Baseline (Day 1), Week 6, Week 12

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

University of Ljubljana

Collaborators

University of Ljubljana, Faculty of Medicine

Investigators

  • Principal Investigator: Rok Bavdek, PhD
  • Study Director: Nejc Umek, MD PhD, Institute of Anatomy, Faculty of Medicine, University of Ljubljana

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

December 16, 2025

Primary Completion (Estimated)

June 30, 2027

Study Completion (Estimated)

December 31, 2027

Study Registration Dates

First Submitted

November 14, 2025

First Submitted That Met QC Criteria

November 14, 2025

First Posted (Actual)

November 19, 2025

Study Record Updates

Last Update Posted (Actual)

June 2, 2026

Last Update Submitted That Met QC Criteria

May 30, 2026

Last Verified

May 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • rPMS, 0124-0043
  • P5-0124, P3-0043 (Other Identifier: Slovenian Research and Innovation Agency (ARIS))

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Plan Description

All de-identified IPD (demographics, primary and secondary outcome measures) will be shared.

IPD Sharing Time Frame

IPD will be available 12 months after publication of the results and will remain available for 5 years.

IPD Sharing Access Criteria

Researchers will be able to request access to IPD. Access will be granted upon reasonable proposals which will be reviewed and approved by the study investigators. Only de-identified datasets will be shared. Data will be provided electronically.

IPD Sharing Supporting Information Type

  • STUDY_PROTOCOL

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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