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

Official title

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.

Overview

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.

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.

Interventions

• 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 executi

Primary outcome measures

• Intra-tendinous sliding between Achilles tendon layers (derived from ultrasound imaging and analyzed using a speckle tracking algorithm) [Time frame: 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 [Time frame: 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 [Time frame: 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 [Time frame: pretest (one week before the 12-week program) and posttest (one week after the 12-week program)]

Secondary outcome measures (9)

• Questionnaire Data: Quality of Life (SF-12 questionnaire) [Time frame: 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 [Time frame: 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) [Time frame: 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) [Time frame: 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 [Time frame: 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 [Time frame: Posttest in the lab (week after the 12-week training program)]
• Questionnaire Data: Achilles Tendinopathy symptoms (TENDINS-A questionnaire) [Time frame: 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) [Time frame: 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)) [Time frame: 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]

Eligibility criteria

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.

Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.

Healthy volunteers: No

Study design

Allocation

Randomized

Model

Parallel assignment

Masking

Single blind

Primary purpose

Treatment

Study locations

Belgium · 1 center

• KU Leuven — Leuven

Publications

• 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. PMID 38898554
• 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. PMID 41572520
• 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. PMID 34187784
• 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. PMID 32469914
• 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. PMID 22764132
• 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. PMID 22279080
• 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. PMID 25150898
• 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. PMID 36640640

Identifiers

NCT: NCT07623408 · S68515

Primary sources (government registries)

• ClinicalTrials.gov (US NIH)

View this study on ClinicalTrials.gov ↗