An interventional study of Tendo device Vibrration and Sham Muscle Vibration in Muscle Fatigue, Exertion, Perceived and Neuromuscular Activity, sponsored by Wrocław University of Science and Technology. Enrolling by invitation at 1 site in Poland. Open to participants aged 18 Years to 26 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-07-20.
Sponsored by Wrocław University of Science and Technology · Not applicable, Interventional, and Basic science
The purpose of this study is to find out if applying mild mechanical vibration (100 Hz) to the the Achilles and patellar tendons before and during exercise can make cycling feel easier and help athletes generate more power. The researchers also want to test if a new, lightweight wearable sleeve called "Tendo" is just as effective at doing this as a stationary laboratory machine. The study will involve 40 healthy, active student-athletes aged 18 to 26. Each participant will attend three separate testing sessions in a laboratory, with at least 48 hours of rest between sessions. During each 85-minute session, participants will:
Complete baseline resting measurements of their muscles and tendons. Ride a stationary exercise bicycle with a covered screen, adjusting their speed and pedaling based only on how hard they feel they are working, using a 0-100 effort scale called Borg CR100.
Receive a 10-minute resting tendon vibration. Repeat the cycling test with a short "booster" vibration to see how their performance changes.
To understand how the vibration works, the researchers will use harmless skin sensors to measure muscle activity (sEMG), a gentle tapping device to check tendon stiffness (MyotonPRO), and ultrasound imaging to look at tendon structure.
Stationary Vibration: High-frequency (100 Hz) vibration from a fixed laboratory machine.
Wearable Vibration: High-frequency (100 Hz) vibration from the portable Tendo sleeve.
Sham Vibration: A low-frequency (15 Hz) vibration that does not trigger a physiological response, serving as a control to make sure the results are not just due to a placebo effect.
The perception of physical exertion (RPE - Rate of Perceived Exertion), most commonly quantified using the Borg scale, constitutes a key neurophysiological mechanism regulating the intensity and duration of human locomotor activity. Traditional models of peripheral fatigue assumed that the exercise capacity limit is directly determined by the homeostatic depletion of muscular energy reserves. However, contemporary sports neurophysiology, drawing on the concept of the Central Governor Model, demonstrates that the central nervous system is the ultimate guardian of human performance.
In this context, a crucial role is played by the phenomena of proprioception and somatosensory signaling generated by musculo-tendinous mechanoreceptors, specifically muscle spindles. These spindles are sensitive to changes in muscle length and the rate of these changes, sending continuous feedback to the CNS via the ascending pathways of the spinal cord. The brain compares these signals with an internal template of motor intention, the so-called efference copy, which serves as a neurological equivalent of the expected energetic expenditure. The convergence or divergence of these two information streams directly shapes the final perception of RPE. Studies from last year (Marchand et al., 2025), upon which our medical experiment is based, proved that this mechanism can be effectively modulated non-pharmacologically using passive, high-frequency mechanostimulation. Applying mechanical vibrations with a frequency of 100 Hz and an amplitude of approximately 1 mm to the tendons induces a phenomenon of neurophysiological receptor jamming. The intense vibration triggers a torrent of proprioceptive impulses, leading to the suppression of spinal reflexes and the attenuation of reaferent signals sent from the muscle spindles to the brain. Consequently, the CNS interprets the movement as "energetically cheaper" and easier. Laboratory studies indicate that decoupling the actual mechanical load from the perception of exertion allows for an increase in actual power output (by up to approximately 20% during submaximal effort) without a simultaneous increase in the subjective feeling of fatigue. Moreover, vibration exhibits protective properties against neuromuscular fatigue, stabilizing exercise parameters in the late stages of training.
This project aims to translate these fundamental laboratory discoveries into applied conditions. Previous research protocols relied on stationary, electrodynamic exciters that required complete immobilization of the subject's limb and the application of vibration in a specific position while stabilizing the exciter, which limited their utility in sports. The answer to this limitation is an interdisciplinary project by the Wrocław University of Science and Technology - a proprietary prototype of the Tendo wearable vibration band. By applying physical parameters identical to laboratory equipment (100 Hz), this device offers full mobility and makes this technology accessible to every athlete.
To precisely verify the research hypothesis and determine the basis of the observed changes, the project involves a three-dimensional diagnostic approach combining neurological, biomechanical, and structural assessments.
The project's results have the potential to revolutionize training support methods, optimize post-exercise neuromuscular recovery, and protect athletes from musculoskeletal overloads, offering the academic and sporting communities a fully safe, scientifically validated, and mobile stimulation tool.
Link to the study upon which we base our work: https://doi.org/10.1016/j.jshs.2025.101061 .
This study is designed as an interdisciplinary, randomized, single-blind, three-arm, counterbalanced crossover trial. The primary objective is to investigate the translation of focal muscle vibration from a stationary laboratory setup to a flexible, low-voltage wearable sleeve (Tendo). Each of the 40 recruited student-athletes will complete three distinct experimental sessions separated by a washout period of at least 48 hours to prevent neuromuscular carryover effects.
Prior to the experimental sessions, participants will attend an online briefing session to learn about the rating of perceived exertion (RPE) using the Borg CR100 scale, distinguishing exertion from muscle pain or discomfort. Following this, they will undergo a physical familiarization session involving a mock incremental test on a cycle ergometer. Group allocation and session order will be determined before the first experimental session using a simple service randomisation via sealedenvelope.com.
sEMG Preparation: Skin over the vastus lateralis muscle of the dominant limb will be shaved, abraded, and cleaned to reduce impedance, in accordance with SENIAM guidelines. Wireless Shimmer3 EMG electrodes will be secured using hypoallergenic gel electrodes and additionally reinforced with medical adhesive tape to prevent detachment due to intense sweating.
Statical ultrasound imaging of the Achilles tendon and patellar ligament will be performed under direct orthopedic supervision. Viscoelastic and biomechanical tissue properties (static tone, dynamic stiffness, and elasticity) will be recorded using the MyotonPRO digital myotonometer.
Participants perform a standardized 6-minute warm-up on a cycle ergometer (4 minutes at moderate self-selected intensity, followed by 2 minutes at strong intensity).
A baseline exercise test is conducted on the cycle ergometer to establish pre-intervention power output values.
Participants rest in a seated position for 12 minutes. For exactly 10 minutes, bilateral focal muscle vibration (100 Hz, 1 mm amplitude) or sham stimulation (15 Hz, 1 mm amplitude) is applied directly to the Achilles and patellar tendons.
During stimulation, participants maintain a 90° flexion at the hip and knee joints, with the ankle in dorsiflexion, ensuring optimal muscle-tendon tension for maximum vibration transmission to the muscle spindles.
Immediately post-exercise and at minutes 15 and 30 of resting recovery, the baseline measurements (MyotonPRO, USG, and static sEMG) are repeated.
Relative percentage changes from baseline (Relative change% = [(Post - Pre) / Pre] * 100%) will be calculated for all biomechanical and neuromuscular parameters.
Safety and Termination Criteria
The study will be immediately terminated for any participant who:
Formally withdraws consent, Reports acute joint/muscle pain, chest tightness, severe dizziness, or nausea, Reaches volitional exhaustion, Exhibits abnormal physiological responses (e.g., erratic heart rate spikes), Experiences any technical malfunction with the stimulation devices,
Wrocław University of Science and Technology is the lead sponsor of 5 studies on the registry; 2 are open to participants now.
Counted across the registry records on this site, refreshed daily.
Exclusion Criteria:
Participants receive muscle vibration delivered via wearable Tendo device. The vibration is applied bilaterally to the Achilles and patellar tendons with a frequency of 100 Hz and an amplitude of 1 mm. This condition consists of a 10-minute resting pre-exercise stimulation followed by a 5-minute "booster" stimulation administered dynamically during movement midway through the cycling protocol to sustain the neurophysiological Tonic Vibration Reflex (TVR).
Device: Tendo device Vibrration · Device: Sham Muscle Vibration · Device: Laboratory control vibration
Participants receive focal muscle vibration delivered via alabpooratory device. The vibration is applied bilaterally to the Achilles and patellar tendons with a frequency of 100 Hz and an amplitude of 1 mm. This condition consists of a 10-minute resting pre-exercise stimulation followed by a 5-minute resting "booster" stimulation administered midway through the cycling protocol to sustain the neurophysiological Tonic Vibration Reflex (TVR).
Device: Tendo device Vibrration · Device: Sham Muscle Vibration · Device: Laboratory control vibration
Participants undergo an identical protocol but receive a low-frequency, non-therapeutic sham stimulation. The stimulation is applied bilaterally to the Achilles and patellar tendons via the Tendo device with a subminimal frequency of 15 Hz and an amplitude of 1 mm. This condition consists of a 10-minute resting pre-exercise sham stimulation followed by a 5-minute booster sham stimulation during the active cycling protocol to control for the acoustic noise, physical presence of the device, and potential placebo effects.
Device: Tendo device Vibrration · Device: Sham Muscle Vibration · Device: Laboratory control vibration
Arm Description: Participants receive focal muscle vibration delivered via a lightweight, wearable Tendo system. The vibration is applied bilaterally to the Achilles and patellar tendons with a frequency of 100 Hz and an amplitude of 1 mm. This condition consists of a 10-minute resting pre-exercise stimulation followed by a 5-minute "booster" stimulation administered dynamically during movement midway through the cycling protocol to sustain the neurophysiological Tonic Vibration Reflex (TVR).
Participants undergo an identical protocol but receive a low-frequency, non-therapeutic sham stimulation. The stimulation is applied bilaterally to the Achilles and patellar tendons via the Tendo sleeve with a subminimal frequency of 15 Hz and an amplitude of 1 mm. This condition consists of a 10-minute resting pre-exercise sham stimulation followed by a 5-minute booster sham stimulation during the active cycling protocol to control for the acoustic noise, physical presence of the device, and potential placebo effects.
Participants receive focal muscle vibration delivered via a stationary laboratory device. The vibration is applied bilaterally to the Achilles and patellar tendons with a frequency of 100 Hz and an amplitude of 1 mm. This condition consists of a 10-minute resting pre-exercise stimulation followed by a 5-minute resting "booster" stimulation administered midway through the cycling protocol to sustain the neurophysiological Tonic Vibration Reflex (TVR).
Mean Power Output
The mean power output (measured in Watts) generated by the participant during the submaximal cycling task. The task is clamp-controlled based on a constant, pre-determined rate of perceived exertion (RPE) on the Borg CR100 scale. Since the perception of effort is kept constant (clamped), the changes in generated power output will reflect the actual physiological and performance efficacy of the focal muscle vibration compared to the sham condition.
Time frame: Continuous recording at 1 Hz, analyzed as the mean power output for each 3-minute block during the cycling task (specifically comparing blocks across the three experimental sessions).
Neuromuscular Activity
Root Mean Square (RMS) of the surface electromyography (sEMG) signal recorded from the vastus lateralis muscle. This parameter assesses changes in neuromuscular excitability, muscle spindle afferent attenuation, and motor unit recruitment strategies.
Time frame: Continuous recording during the cycling task, and static recordings with isometric contraction and with no contraction at baseline, immediately post-exercise, 15 minutes, and 30 minutes of recovery.
Biomechanical and Viscoelastic Tissue Properties
Dynamic stiffness, static tone, and logarithmic decrement of the Achilles tendon and patellar ligament measured non-invasively using the MyotonPRO digital myotonometer. This evaluates whether focal vibration alters the intrinsic mechanical properties of the tissue or works purely through neural pathways.
Time frame: Recorded at baseline, immediately post-exercise, 15 minutes, and 30 minutes of recovery.
Tendon Morphological Structure (Ultrasound)
Cross-sectional area and structural echogenicity of the Achilles tendon and patellar ligament measured via real-time musculoskeletal ultrasound to monitor immediate morphological responses to mechanical stimulation.
Time frame: Recorded at baseline, immediately post-exercise, 15 minutes, and 30 minutes of recovery.
Physiological and Kinematic Strain
Heart rate measured in beats per minute via Polar H10 chest strap and pedaling cadence measured in revolutions per minute via ergometer. These metrics assess physiological cost and movement efficiency under constant perceived exertion.
Time frame: Continuous recording during cycling task, recorded at baseline, immediately post-exercise, 15 minutes, and 30 minutes of recovery.
Plan to share: Yes — De-identified individual participant data, including physiological, biomechanical, and neuromuscular parameters that underlie the results reported in future publications will be made available to academic researchers to facilitate scientific collaboration and validation of the findings.
Supporting information: Study protocol, Sap, Icf, Csr, Analytic code
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