An interventional study of Neuromuscular Electrical Stimulation (NMES) in Achilles Tendinopathy (AT) and Achilles Tendon Rupture, sponsored by University of Brasilia. Recruiting at 1 site in Brazil. Open to participants aged 18 Years to 60 Years. Per ClinicalTrials.gov, last updated 2026-03-06.
Sponsored by University of Brasilia · Not applicable, Interventional, and Treatment
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.
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.
10,054 studies on the registry are indexed under Pain; 1,649 are open to participants now.
This study's planned enrollment of 30 is below the median of 66 across 8,493 interventional studies indexed under Pain.
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In this group, participants will perform three sets of 10 repetitions of the single leg heel rise functional task without the application of electrical stimulation. Immediately after each set, pain level, functional performance, peripheral oxygen extraction, and maximal Achilles tendon displacement will be assessed.
Under this condition, participants will perform three sets of 10 repetitions of the single leg heel rise functional task with superimposed electrical stimulation applied at the maximum tolerated intensity, characterized by visible muscle contraction and associated with a self-reported discomfort level between 8 and 10 on the Numeric Rating Scale. Immediately after each set, pain level, functional performance, peripheral oxygen extraction, and maximal Achilles tendon displacement will be assessed.
Device: Neuromuscular Electrical Stimulation (NMES)
For this condition, participants will perform three sets of 10 repetitions of the single leg heel rise functional task with superimposed sham electrical stimulation. Electrical stimulation parameters will initially be configured identically to those used in the active intervention. However, to ensure adequate blinding, stimulation will be applied for approximately 40 seconds and then gradually reduced until complete cessation. From this point onward, no additional current will be delivered, although the device will remain on and the electrodes will remain in place throughout the test. Immediately after each set, pain level, functional performance, peripheral oxygen extraction, and maximal Achilles tendon displacement will be assessed.
Device: Neuromuscular Electrical Stimulation (NMES)
In this condition, participants will perform three sets of 10 repetitions of the single leg heel rise functional task with superimposed electrical stimulation applied at the sensory level, defined as the highest intensity that does not elicit visible muscle contraction. Immediately after each set, pain level, functional performance, peripheral oxygen extraction, and maximal Achilles tendon displacement will be assessed.
Device: Neuromuscular Electrical Stimulation (NMES)
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.
Pain level
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.
Time frame: Immediately after the performance of the functional task
Total time
The total time (s) during the single-leg heel rise task will be measured using the MuscleLab® system.
Time frame: Immediately after the performance of the functional task.
Maximal displacement
The maximal displacement (cm) during the single-leg heel rise task will be measured using the MuscleLab® system.
Time frame: Immediately after the performance of the functional task.
Total work
The total work (J) during the single-leg heel rise task will be measured using the MuscleLab® system.
Time frame: Immediately after the performance of the functional task.
Total power
The total power (W) during the single-leg heel rise task will be measured using the MuscleLab® system.
Time frame: Immediately after the performance of the functional task.
Number of repetitions
The number of repetitions completed during the single-leg heel rise task will be recorded using the MuscleLab® system.
Time frame: Immediately after the performance of the functional task.
Peripheral oxygen extraction
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.
Time frame: Immediately after the performance of the functional task.
Maximal Achilles tendon displacement
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.
Time frame: Immediately after the performance of the functional task.
Lenght of achilles tendon
The total and free length (cm) of the Achilles tendon will be measured using portable ultrasonography.
Time frame: Baseline (prior to Block A only)
Thickness of achilles tendon
The thickness (mm) of the Achilles tendon will be measured using portable ultrasonography.
Time frame: Baseline (prior to Block A only)
Cross-sectional area of achilles tendon
The cross-sectional area (cm²) of the Achilles tendon will be measured using portable ultrasonography.
Time frame: Baseline (prior to Block A only)
Presence of neovascularization of the Achilles tendon
The presence of neovascularization of the Achilles tendon will be assessed using portable ultrasonography.
Time frame: Baseline (prior to Block A only)
Elastic modulus
The median elastic modulus (kPa) of the Achilles tendon will be measured using shear wave elastography.
Time frame: Baseline (prior to Block A only)
Shear wave velocity
The median shear wave velocity (m/s) of the Achilles tendon will be measured using shear wave elastography.
Time frame: Baseline (prior to Block A only)
Depth
The measurement depth (cm) of the Achilles tendon during elastography assessment will be recorded using shear wave elastography.
Time frame: Baseline (prior to Block A only)
Isometric strength
Isometric strength will be assessed using an isokinetic dynamometer, based on peak isometric torque (N/m) during plantar flexion at 0°.
Time frame: Baseline (prior to Block A only)
Plan to share: No
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Started Jan 2026 (actual). Primary completion is estimated for Aug 2029, 43 months after the start.
Of 3,731 non-industry interventional studies with no phase under Pain, half reached primary completion within 10 months of starting (the median), counting those still running; a quarter within 4 and three quarters within 23. This study's planned 43 months is above that.
Counting every sponsor, half of 3,830 studies reached it within 10 months; a quarter within 4 and three quarters within 23.
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