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NCT Number: NCT07453485

Immediate Effects of Neuromuscular Electrical Stimulation on Pain and Function in Achilles Tendon Disorders

The Achilles tendon exhibits high tensile strength and can withstand extremely high loads. However, it is susceptible to injuries such as tendinopathies and ruptures, which are associated with structural alterations and loss of function. Strategies have been investigated to enhance clinical rehabilitation. Nevertheless, the effects of neuromuscular electrical stimulation on pain and functional improvement, as well as the optimal dosing parameters for the rehabilitation of Achilles tendon injuries, remain inconclusive. The aim of this study is to compare the immediate effects of two electrical stimulation protocols on pain, functional performance, peripheral oxygen extraction, and maximal tendon displacement during a single leg heel rise functional task in patients with Achilles tendinopathy and/or a history of Achilles tendon rupture. In addition, this study aims to characterize Achilles tendon structural properties and ankle plantarflexor muscle strength in this population.

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Key information

Conditions

Achilles Tendinopathy (AT) Achilles Tendon Rupture Neurologic Manifestations Pain Pathological Conditions, Signs and Symptoms Signs and Symptoms

Age range

18 year–60 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

About this study

All groups will be composed of participants with a primary complaint of pain and/or a history of previous Achilles tendon rupture. Participants will perform the interventions in two blocks separated by a seven-day interval (wash-out). Block A: (1) control without active intervention and (2) electrical stimulation applied at the maximum tolerated intensity. Block B: (3) control with sham stimulation and (4) sensory-level electrical stimulation. Block A will always be performed first, followed by Block B. Interventions within each block will be conducted in three sets of 10 repetitions, totaling six sets per day.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Primary complaint of pain localized in the midportion (2-6 cm proximal to the calcaneus) or insertion of the Achilles tendon, and/or a history of Achilles tendon rupture occurring at least 3 months prior to assessment.
  • Pain on palpation of the Achilles tendon.
  • Pain during load-bearing activities

Exclusion criteria

  • Exclusive diagnosis of bursitis confirmed by ultrasonographic assessment
  • Any other lower limb injury
  • History of lower limb surgery within the past year
  • Previous Achilles tendon tenoplasty performed less than 3 months prior to assessment

Treatment and study plan

Neuromuscular Electrical Stimulation (NMES)

Device

Neuromuscular electrical stimulation-induced contractions will be delivered using an electrical stimulator connected to a pair of 5×5 cm self-adhesive surface electrodes. Stimulation will be applied in a superimposed manner during voluntary movement, at a frequency of 75 Hz and a phase duration of 400 µs.

Primary outcomes

  1. Pain level

    Time frame: Immediately after the performance of the functional task

    Pain intensity during the single leg heel rise task will be assessed using the Visual Analog Scale, consisting of a numerical scale ranging from 0 to 10 points, in which 0 represents no pain and 10 corresponds to the worst pain ever experienced by the participant.

Secondary outcomes

  1. Total time

    Time frame: Immediately after the performance of the functional task.

    The total time (s) during the single-leg heel rise task will be measured using the MuscleLab® system.

  2. Maximal displacement

    Time frame: Immediately after the performance of the functional task.

    The maximal displacement (cm) during the single-leg heel rise task will be measured using the MuscleLab® system.

  3. Total work

    Time frame: Immediately after the performance of the functional task.

    The total work (J) during the single-leg heel rise task will be measured using the MuscleLab® system.

  4. Total power

    Time frame: Immediately after the performance of the functional task.

    The total power (W) during the single-leg heel rise task will be measured using the MuscleLab® system.

  5. Number of repetitions

    Time frame: Immediately after the performance of the functional task.

    The number of repetitions completed during the single-leg heel rise task will be recorded using the MuscleLab® system.

  6. Peripheral oxygen extraction

    Time frame: Immediately after the performance of the functional task.

    Oxygen extraction of the periarticular ankle muscles will be assessed using near-infrared spectroscopy, with the sensor positioned on the skin over the lateral gastrocnemius muscle during the single leg heel rise task. Variations in oxy- and deoxy-hemo/myoglobin (O₂Hb and HHb, respectively) will be recorded in arbitrary units at a sampling frequency of 25 Hz.

  7. Maximal Achilles tendon displacement

    Time frame: Immediately after the performance of the functional task.

    Maximal Achilles tendon displacement (%) will be measured using a transducer positioned over the myotendinous junction of the gastrocnemius muscles, secured to a specific support, during the single leg heel rise task. Maximal displacement will be determined based on the change in Achilles tendon length relative to its resting length.

  8. Lenght of achilles tendon

    Time frame: Baseline (prior to Block A only)

    The total and free length (cm) of the Achilles tendon will be measured using portable ultrasonography.

  9. Thickness of achilles tendon

    Time frame: Baseline (prior to Block A only)

    The thickness (mm) of the Achilles tendon will be measured using portable ultrasonography.

  10. Cross-sectional area of achilles tendon

    Time frame: Baseline (prior to Block A only)

    The cross-sectional area (cm²) of the Achilles tendon will be measured using portable ultrasonography.

  11. Presence of neovascularization of the Achilles tendon

    Time frame: Baseline (prior to Block A only)

    The presence of neovascularization of the Achilles tendon will be assessed using portable ultrasonography.

  12. Elastic modulus

    Time frame: Baseline (prior to Block A only)

    The median elastic modulus (kPa) of the Achilles tendon will be measured using shear wave elastography.

  13. Shear wave velocity

    Time frame: Baseline (prior to Block A only)

    The median shear wave velocity (m/s) of the Achilles tendon will be measured using shear wave elastography.

  14. Depth

    Time frame: Baseline (prior to Block A only)

    The measurement depth (cm) of the Achilles tendon during elastography assessment will be recorded using shear wave elastography.

  15. Isometric strength

    Time frame: Baseline (prior to Block A only)

    Isometric strength will be assessed using an isokinetic dynamometer, based on peak isometric torque (N/m) during plantar flexion at 0°.

Study contacts

Contact information is provided by the study sponsor or research team.

José RS Júnior, PhD

CONTACT

[email protected]

+55 61 3107-8450

João LQ Durigan, PhD

CONTACT

[email protected]

+55 61 3107-8450

Sponsors and collaborators

Lead sponsor

University of Brasilia

Other

Registry information

Official study title

Immediate Effects of Neuromuscular Electrical Stimulation on Pain and Functional Performance in Individuals With Achilles Tendinopathy and Tendon Rupture: A Randomized Crossover Clinical Trial

Important dates

Study start
2026
Primary completion
2029
Study completion
2029
First posted
Mar 6, 2026
Registry last updated
Mar 6, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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