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| Name | Class |
|---|---|
| Universitaire Ziekenhuizen KU Leuven | OTHER |
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This study will investigate whether a 12-week load-based exercise program performed with an externally rotated foot position ("toes-out") leads to different changes in intra-tendinous sliding, symptoms, and function compared to a standard exercise program performed with a neutral foot position in individuals with mid-portion Achilles tendinopathy. In addition, physical activity will be monitored during and after the intervention to examine how daily loading patterns relate to symptoms and functional recovery over a 6-month period.
Achilles tendinopathy is a common overuse disorder characterized by pain, swelling, and impaired function, with substantial impact on sports participation and quality of life. Despite exercise therapy being considered the gold standard treatment, rehabilitation outcomes remain suboptimal, with a considerable proportion of patients reporting persistent symptoms and many failing to return to their preferred level of sport. This highlights the need to improve current rehabilitation strategies and better understand mechanisms underlying tendon recovery.
The Achilles tendon is mechanically complex, as it is loaded by the triceps surae muscle group and can be considered to consist of three partially independent subtendons that slide relative to each other. This intra-tendinous sliding has been investigated during passive and active loading tasks and may represent an important feature of healthy tendon behavior. It has been proposed that sliding may help distribute stress within the tendon and may contribute to tendon adaptation through local shear-related mechanobiological responses.
Emerging evidence suggests that intra-tendinous sliding is altered in tendinopathy. Previous work has demonstrated reduced sliding in pathological tendons compared to healthy controls, while external foot rotation ("toes-out") has been shown to increase sliding during isometric and dynamic loading tasks. These findings raise the possibility that modifying foot position during rehabilitation exercises may influence internal tendon loading and promote more favorable adaptations. However, no studies have investigated changes in intra-tendinous sliding longitudinally during an exercise therapy program or whether modifying foot position during rehabilitation affects clinical outcomes.
This study will therefore compare two 12-week load-based rehabilitation programs for individuals with mid-portion Achilles tendinopathy: a standard program performed with a neutral foot position and an adapted program performed with an externally rotated foot position. The study will investigate whether these interventions lead to different changes in intra-tendinous sliding, tendon morphology, symptoms, and functional recovery.
In addition to the prescribed exercise intervention, the study will investigate the role of daily physical activity in rehabilitation outcomes. Tendon loading occurs not only during structured exercise therapy but also through habitual and sport-related activity, which may influence recovery. However, little is currently known about how physical activity patterns change during and after rehabilitation or how these patterns relate to symptoms and function.
Physical activity will therefore be monitored throughout the intervention and follow-up period to evaluate changes in activity behavior over time and to explore associations between daily loading patterns, symptom progression, and functional outcomes. By combining evaluation of tendon-specific mechanical adaptations with monitoring of physical activity behavior, this study aims to provide new insights into factors influencing recovery in Achilles tendinopathy and to inform optimization of rehabilitation strategies.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| Toes-out Training Group | Experimental | Patients in this group will perform the 12-week load-based exercise program, and will execute all exercises daily througout the full program with toes-out (the feet horizontally outwards rotated). For this toes-out angle, their individual, most comfortable angle is chosen. |
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| Neutral Training Group | Active Comparator | Patients in this group will perform the 12-week load-based exercise program, and will execute all exercises daily througout the full program with a neutral foot position. |
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| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| 12-week adaptive, load-based exercise therapy protocol for Achilles Tendinopathy | Other | A 12-week progressive, load-based exercise program was developed, consisting of four daily exercises with gradually increasing tendon load over time. The program was based on the exercise battery and according Achilles Tendon loading index described by Baxter et al. (2021) and included a wide variety of 30 exercises (heel raise variations, step exercises, squats, lunges, jump variations, ...). A new exercise was introduced every four days, while weekly supervised sessions ensured correct execution and allowed for adjustments based on patient tolerance (e.g., excessive knee loading, too high pain scores during specific exercises, …). This flexible approach enabled gradual progression of each participant's daily load index according to individual capacity. An estimated time of 20-30 minutes daily is needed to execute all the daily exercises. |
| Measure | Description | Time Frame |
|---|---|---|
| Intra-tendinous sliding between Achilles tendon layers (derived from ultrasound imaging and analyzed using a speckle tracking algorithm) | Ultrasound images of the Achilles tendon will be recorded using a probe (Hitachi L64, Tokyo, Japan) put in an external probeholder during multiple rehabilitation exercises: Birise Bidrop Standing, Unirise Unidrop Standing Knee Extended, Unirise Unidrop Standing Knee Bent and squat. The device we will use is the Arietta 650, FUJIFILM, which allows to record B-mode ultrasound images. The probe will be placed distally on the Achilles tendon, just above the calcaneal insertion (used as reference point). Using a speckle tracking algorithm in Matlab, the displacement of 6 rows within the Achilles tendon is calculated. Intra-tendinous sliding is calculated as the relative difference between the displacement of the superficial and deep border. | Measured during the pre and posttest, respectively the week before and after the 12-week exercise therapy program |
| Clinical outcomes after Achilles Tendinopathy rehabilitation: Achilles Tendinopathy symptoms based on VISA-A questionnaire | At pretest, 3, 6, 9, posttest, 15, 18, 21, and 24, the VISA-A questionnaire will be completed online. During the pre- and post-test assessments, participants will complete the questionnaire on a laptop provided in the lab, ensuring it is administered online and in the same manner as throughout the intervention, where they fill it in at home. The VISA-A questionnaire is an 8-item survey used to assess the severity of Achilles tendinopathy. It evaluates pain, daily functional activities, and sporting ability, with scores ranging from 0 to 100, where a score of 100 indicates no symptoms. | Pretest (one week before the 12-week program), Posttest (one week after the 12-week program), and at week 3,6,9,15,18,21 and 24. |
| Clinical outcomes after Achilles Tendinopathy rehabilitation: Achilles Tendon functionality based on heel-rise test | Heel-rise test: participants perform as many heel-raises as possible at a frequency of 25 per minute (controlled by a metronome). The test will be discontinued when the participant does not reach maximum height, cannot keep the frequency, cannot keep the knee straight or stops due to pain or fatigue. By using an application, the foot will be filmed and heel work will be calculated. |
| Measure | Description | Time Frame |
|---|---|---|
| Questionnaire Data: Quality of Life (SF-12 questionnaire) | SF-12 questionnaire: used to assess health-related quality of life. | Pretest (one week before the 12-week training program), Posttest (one week after the 12-week training program), week 3,6,9,15,18,21,24 |
| Doppler Vascularity |
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The following inclusion criteria will be used:
PATIENTS WITH ACHILLES TENDINOPATHY:
Prior to start of the data collection, these inclusion criteria (specifically the ones concerning Achilles Tendinopathy presence) will be checked by a medical doctor at SMAC (Sports medical advisory centre Leuven). Only if they confirm the diagnosis, patients are included in the study.
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| Name | Role | Phone | Extension | |
|---|---|---|---|---|
| Laura Lecompte, Msc | Contact | +32499263609 | laura.lecompte@kuleuven.be | |
| Marion Crouzier, PhD | Contact | +33 620045744 | marion.crouzier@univ-nantes.fr |
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| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| KU Leuven | Recruiting | Leuven | Vlaams-Brabant | 3000 | Belgium |
| PubMed Identifier | Type | Citation | Retractions |
|---|---|---|---|
| 38898554 | Background | Lecompte L, Crouzier M, Bogaerts S, Scheys L, Vanwanseele B. Reduced Intratendinous Sliding in Achilles Tendinopathy During Active Plantarflexion Regardless of Horizontal Foot Position. Scand J Med Sci Sports. 2024 Jun;34(6):e14679. doi: 10.1111/sms.14679. | |
| 41572520 | Background | Lecompte L, Crouzier M, Bogaerts S, Vanwanseele B. Patients with Achilles Tendinopathy Show Reduced Intratendinous Sliding during Dynamic Exercises. Med Sci Sports Exerc. 2026 Jun 1;58(6):1149-1158. doi: 10.1249/MSS.0000000000003942. Epub 2026 Jan 22. |
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Individual data of all outcome measures (primary and secondary outcome parameters) will be analyzed and shared upon request.
Data will be available once published in a peer-reviewed manuscript online and this with no end-date.
People will be able to request data access through e-mail with explanation why it would be interesting for them to have the detailed individual data of (certain) outcome parameters.
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Two groups will follow the same exercise therapy program of 12 weeks with daily exercises for Achilles Tendinopathy where the intensity gradually increases over the weeks. One group will perform all exercises in a Neutral foot position whereas the other group will perform all exercises with the toes outwards rotated (toes-out foot position).
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| Pretest (one week before the 12-week program) and Posttest (one week after the 12-week program) |
| Clinical outcomes after Achilles Tendinopathy rehabilitation: Achilles Tendon functionality based on hopping till pain test | • Hopping till pain: the participant hops on a single leg at a pace of 2 jumps per second (controlled by a metronome) where the goal is to achieve 25 pain-free hops, but the test will be stopped when the participant starts to experience pain. | pretest (one week before the 12-week program) and posttest (one week after the 12-week program) |
Intra-tendinous vascularity will be assessed in the sagittal plane with Doppler Ultrasonography (Arietta 650, FUJIFILM). The ultrasound transducer will be aligned parallel to the tendon and will be applied with no pressure and it will be positioned so that it visualizes the proximal portion of the calcaneal bone and the Achilles tendon. For this, participants will be in prone position with the knee extended and the ankle joint passively stabilized at 90°. Three scans with a duration of 4 seconds will be recorded at both the insertion and midportion of the tendon after all rehabilitation exercises in the lab are performed. |
| Pretest and posttest, respectively one week before and after the 12-week exercise therapy program |
| Morphological features of the Achilles tendon (free Achilles tendon length and volume) | During rest in the prone position, multiple scans of the lower leg will be acquired using 3D freehand ultrasound. This technique combines conventional B-mode ultrasonography (FUJIFILM Healthcare, Arietta 650DI) with a motion analysis system to generate in vivo three-dimensional reconstructions of tendon structures. The 2D ultrasound images will be transformed into a global coordinate system using the open-source medical image computing and visualization software 3D Slicer, enabling reconstruction of a 3D tendon volume. Based on this technique, the length and volume of the free Achilles tendon (AT) will be estimated. As a supplementary check, free AT length will also be measured manually by determining the distance between the calcaneal insertion and the soleus myotendinous junction, identified using ultrasound imaging. In addition, two ultrasound images (transverse and sagittal planes) will be obtained at the swollen region of the tendon to provide indications of tendon width. | Pretest and posttest, respectively one week before and after the 12-week exercise therapy program |
| Lower extremity biomechanics during rehabilitation exercises: kinematics, kinetics, muscle activations, muscle forces and cumulative Achilles Tendon load through musculoskeletal modeling (assesed with 3D motion and ground reaction force capturing) | In the lab, patients will perform four rehabilitation exercises: Bilateral heel raise-drop, unilateral heel raise-drop (knee extended and knee bent version) and squat. Besides that, walking and optionally (if the patient can) running on the treadmill. 3D-motion capture data, EMG (Delsys electrodes) and force plate data will be collected. Through musculoskeletal modeling in OpenSim, Kinematics, kinetics, muscle activations and forces (of Gastrocnemius medialis (GM) and lateralis (GL), soleus (SOL), tibialis posterior and anterior and peroneus) will be analyzed. Besides that, EMG will be recorded through Delsys electrodes on Gastrocnemius medialis and lateralis, soleus, tibialis anterior and peroneus. Achilles Tendon Load will be calculated as the sum of the tendon force from GM, GL and SOL from the musculoskeletal model - muscle analysis after dynamic optimization. | During the pretest and posttest in the lab, respectively one week before and after the 12-week training program |
| Physical activity throughout the training program | Throughout the training program (and also the 12 weeks after as follow-up), all patients wear a Fitbit Inspire 3. This activity tracker will measure the physical activity of the patient. Most important features here are amount of daily steps and automatically tracked activities (cycling, swimming, running, walking) with according time. Besides that, all patients have a logbook where they write down every week as well which activities they did as an extra check-up. (The logbook is only used during the training program). | Daily for 6 months: 12 weeks during the training program and 12 weeks after the training program. |
| Interview on patient perception after the training program | During the post-test assessment in the lab, following the 12-week training program, a live interview will be conducted with each participant. The principal investigator will ask questions regarding the participant's experiences with the training program. The interview will include both open-ended questions and closed-ended questions using a Likert scale. It will take approximately 10 minutes and will provide important information regarding the feasibility of the program for patients performing 30 minutes of exercises daily. | Posttest in the lab (week after the 12-week training program) |
| Questionnaire Data: Achilles Tendinopathy symptoms (TENDINS-A questionnaire) | TENDINS-A questionnaire: a patient-reported outcome measure (PROM) designed to assess the severity of disability in individuals with Achilles tendinopathy. It evaluates pain, symptoms, and physical function to determine the impact of the condition on daily life. As this questionnaire was only recently developed and published in 2024, limited research is available on how its outcomes relate to the VISA-A. Therefore, collecting both measures at pre- and post-test will allow comparison between the two instruments. | Pretest (one week before the 12-week training program), Posttest (one week after the training program), week 3,6,9,15,18,21,24 |
| Questionnaire Data: return to sport (13-item FRESS questionnaire) | 13-item FRESS questionnaire: used to assess return-to-sport outcomes. | Pretest (one week before the 12-week training program), Posttest (one week after the 12-week training program), week 3,6,9,15,18,21,24 |
| Questionnaire Data: fear of movement (Tampa Scale for Kinesiophobia (TSK)) | Tampa Scale for Kinesiophobia (TSK): used to assess fear of movement and reinjury. | Pretest (one week before the 12-week training program), Posttest(one week after the 12-week training program), week 3,6,9,15,18,21,24 |
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