Effect of Foot Position During Rehabilitation of Achilles Tendinopathy on Tendon Mechanics and Symptoms.

The Effect of Foot Positioning During a 12-week Supervised Training Program on Achilles Tendon Mechanics and Function in Individuals With Mid-portion Achilles Tendinopathy.

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.

Study Overview

• Status: Recruiting
• Conditions: Achilles Tendinopathy (AT)
• Intervention / Treatment: Other: 12-week adaptive, load-based exercise therapy protocol for Achilles Tendinopathy

Detailed Description

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.

• Study Type: Interventional
• Enrollment (Estimated): 60
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Laura Lecompte, Msc; Phone Number: +32499263609; Email: laura.lecompte@kuleuven.be
• Study Contact Backup: Name: Marion Crouzier, PhD; Phone Number: +33 620045744; Email: marion.crouzier@univ-nantes.fr

Study Locations

• Belgium
  • Vlaams-Brabant
    • Leuven, Vlaams-Brabant, Belgium, 3000
      • Recruiting
      • KU Leuven
      • Contact: Benedicte Vanwanseele, Prof; Phone Number: +32499263609; Email: benedicte.vanwanseele@kuleuven.be

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

The following inclusion criteria will be used:

PATIENTS WITH ACHILLES TENDINOPATHY:

• Voluntary written Informed consent of the participant or their legally authorized representative has been obtained prior to any screening procedures.
• Age between 18 and 65 years old
• BMI between 18.5-30
• Showing history of intermittent episodes of Achilles tendon pain lasting more than 3 consecutive weeks within the past 6 months.
• Presenting palpable focal thickening of the Achilles tendon.
• Having pain originating from the Achilles tendon on palpation of thickened tendon and on loading activities (such as running, jumping).
• Showing sonographic evidence of tendinopathy, i.e. focal thickening and hypoechocity, consistent with previously reported sonographic characteristics diagnosed of 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.

Study Plan

How is the study designed?

Design Details

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

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Toes-out Training Group; 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.	Other: 12-week adaptive, load-based exercise therapy protocol for Achilles Tendinopathy; 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.
Active Comparator: Neutral Training Group; 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.	Other: 12-week adaptive, load-based exercise therapy protocol for Achilles Tendinopathy; 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.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	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.	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)

Secondary Outcome Measures

Outcome Measure	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	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

Collaborators and Investigators

• Sponsor: KU Leuven
• Collaborators: Universitaire Ziekenhuizen KU Leuven

Publications and helpful links

General Publications

• Franz JR, Slane LC, Rasske K, Thelen DG. Non-uniform in vivo deformations of the human Achilles tendon during walking. Gait Posture. 2015 Jan;41(1):192-7. doi: 10.1016/j.gaitpost.2014.10.001. Epub 2014 Oct 12.
• Robinson JM, Cook JL, Purdam C, Visentini PJ, Ross J, Maffulli N, Taunton JE, Khan KM; Victorian Institute Of Sport Tendon Study Group. The VISA-A questionnaire: a valid and reliable index of the clinical severity of Achilles tendinopathy. Br J Sports Med. 2001 Oct;35(5):335-41. doi: 10.1136/bjsm.35.5.335.
• van der Plas A, de Jonge S, de Vos RJ, van der Heide HJ, Verhaar JA, Weir A, Tol JL. A 5-year follow-up study of Alfredson's heel-drop exercise programme in chronic midportion Achilles tendinopathy. Br J Sports Med. 2012 Mar;46(3):214-8. doi: 10.1136/bjsports-2011-090035. Epub 2011 Nov 10.
• Kujala UM, Sarna S, Kaprio J. Cumulative incidence of achilles tendon rupture and tendinopathy in male former elite athletes. Clin J Sport Med. 2005 May;15(3):133-5. doi: 10.1097/01.jsm.0000165347.55638.23.
• de Vos RJ, van der Vlist AC, Zwerver J, Meuffels DE, Smithuis F, van Ingen R, van der Giesen F, Visser E, Balemans A, Pols M, Veen N, den Ouden M, Weir A. Dutch multidisciplinary guideline on Achilles tendinopathy. Br J Sports Med. 2021 Oct;55(20):1125-1134. doi: 10.1136/bjsports-2020-103867. Epub 2021 Jun 29.
• Radovanovic G, Bohm S, Peper KK, Arampatzis A, Legerlotz K. Evidence-Based High-Loading Tendon Exercise for 12 Weeks Leads to Increased Tendon Stiffness and Cross-Sectional Area in Achilles Tendinopathy: A Controlled Clinical Trial. Sports Med Open. 2022 Dec 20;8(1):149. doi: 10.1186/s40798-022-00545-5.
• 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.
• 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.
• Turner J, Malliaras P, Goulis J, Mc Auliffe S. "It's disappointing and it's pretty frustrating, because it feels like it's something that will never go away." A qualitative study exploring individuals' beliefs and experiences of Achilles tendinopathy. PLoS One. 2020 May 29;15(5):e0233459. doi: 10.1371/journal.pone.0233459. eCollection 2020.
• Thorpe CT, Udeze CP, Birch HL, Clegg PD, Screen HR. Specialization of tendon mechanical properties results from interfascicular differences. J R Soc Interface. 2012 Nov 7;9(76):3108-17. doi: 10.1098/rsif.2012.0362. Epub 2012 Jul 4.
• Tardioli A, Malliaras P, Maffulli N. Immediate and short-term effects of exercise on tendon structure: biochemical, biomechanical and imaging responses. Br Med Bull. 2012 Sep;103(1):169-202. doi: 10.1093/bmb/ldr052. Epub 2012 Jan 25.
• Slane LC, Thelen DG. Non-uniform displacements within the Achilles tendon observed during passive and eccentric loading. J Biomech. 2014 Sep 22;47(12):2831-5. doi: 10.1016/j.jbiomech.2014.07.032. Epub 2014 Aug 8.
• Sancho I, Willy RW, Morrissey D, Malliaras P, Lascurain-Aguirrebena I. Achilles tendon forces and pain during common rehabilitation exercises in male runners with Achilles tendinopathy. A laboratory study. Phys Ther Sport. 2023 Mar;60:26-33. doi: 10.1016/j.ptsp.2023.01.002. Epub 2023 Jan 10.
• Passini FS, Jaeger PK, Saab AS, Hanlon S, Chittim NA, Arlt MJ, Ferrari KD, Haenni D, Caprara S, Bollhalder M, Niederost B, Horvath AN, Gotschi T, Ma S, Passini-Tall B, Fucentese SF, Blache U, Silvan U, Weber B, Silbernagel KG, Snedeker JG. Shear-stress sensing by PIEZO1 regulates tendon stiffness in rodents and influences jumping performance in humans. Nat Biomed Eng. 2021 Dec;5(12):1457-1471. doi: 10.1038/s41551-021-00716-x. Epub 2021 May 24.
• Maffulli N, Sharma P, Luscombe KL. Achilles tendinopathy: aetiology and management. J R Soc Med. 2004 Oct;97(10):472-6. doi: 10.1177/0141076809701004. No abstract available.
• Gheidi N, Kernozek TW, Willson JD, Revak A, Diers K. Achilles tendon loading during weight bearing exercises. Phys Ther Sport. 2018 Jul;32:260-268. doi: 10.1016/j.ptsp.2018.05.007. Epub 2018 May 10.
• Fernandez MR, Athens J, Balsalobre-Fernandez C, Kubo M, Hebert-Losier K. Concurrent validity and reliability of a mobile iOS application used to assess calf raise test kinematics. Musculoskelet Sci Pract. 2023 Feb;63:102711. doi: 10.1016/j.msksp.2022.102711. Epub 2022 Dec 20.
• Demangeot Y, Whiteley R, Gremeaux V, Degache F. The load borne by the Achilles tendon during exercise: A systematic review of normative values. Scand J Med Sci Sports. 2023 Feb;33(2):110-126. doi: 10.1111/sms.14242. Epub 2022 Nov 9.
• Crouzier M, Dandois F, Sarcher A, Bogaerts S, Scheys L, Vanwanseele B. External rotation of the foot position during plantarflexion increases non-uniform motions of the Achilles tendon. J Biomech. 2022 Aug;141:111232. doi: 10.1016/j.jbiomech.2022.111232. Epub 2022 Jul 22.
• Couppe C, Svensson RB, Josefsen CO, Kjeldgaard E, Magnusson SP. Ultrasound speckle tracking of Achilles tendon in individuals with unilateral tendinopathy: a pilot study. Eur J Appl Physiol. 2020 Mar;120(3):579-589. doi: 10.1007/s00421-020-04317-5. Epub 2020 Feb 14.
• Bogaerts S, De Brito Carvalho C, Scheys L, Desloovere K, D'hooge J, Maes F, Suetens P, Peers K. Evaluation of tissue displacement and regional strain in the Achilles tendon using quantitative high-frequency ultrasound. PLoS One. 2017 Jul 20;12(7):e0181364. doi: 10.1371/journal.pone.0181364. eCollection 2017.
• Baxter JR, Corrigan P, Hullfish TJ, O'Rourke P, Silbernagel KG. Exercise Progression to Incrementally Load the Achilles Tendon. Med Sci Sports Exerc. 2021 Jan;53(1):124-130. doi: 10.1249/MSS.0000000000002459.
• Arndt A, Bengtsson AS, Peolsson M, Thorstensson A, Movin T. Non-uniform displacement within the Achilles tendon during passive ankle joint motion. Knee Surg Sports Traumatol Arthrosc. 2012 Sep;20(9):1868-74. doi: 10.1007/s00167-011-1801-9. Epub 2011 Nov 27.

Study record dates

Study Major Dates

• Study Start (Actual): February 19, 2026
• Primary Completion (Estimated): August 31, 2027
• Study Completion (Estimated): August 31, 2027

Study Registration Dates

• First Submitted: May 5, 2026
• First Submitted That Met QC Criteria: May 28, 2026
• First Posted (Actual): June 3, 2026

Study Record Updates

• Last Update Posted (Actual): June 3, 2026
• Last Update Submitted That Met QC Criteria: May 28, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: Rehabilitation; Achilles Tendon; Achilles Tendinopathy; Exercise therapy program; Foot position; homogeneous motions
• Other Study ID Numbers: S68515

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: Individual data of all outcome measures (primary and secondary outcome parameters) will be analyzed and shared upon request.
• IPD Sharing Time Frame: Data will be available once published in a peer-reviewed manuscript online and this with no end-date.
• IPD Sharing Access Criteria: 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.
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; ICF

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No