Muscle Architecture vs Alfredson Protocol in Achilles Tendinopathy

NCT07178418 | Not Yet Recruiting DMC

• 1 other identifier: Muscle Architecture
• Study Type: interventional
• Target: 20
• Locations: 1 country
• Sites: 2

Brief Summary

Achilles tendinopathy is a frequent overuse disorder caused by repetitive loading of the tendon, particularly observed in athletes and middle-aged men. It is typically characterized by mid-portion pain, stiffness in the morning, and functional limitations, with structural alterations such as thickening and disrupted collagen alignment. Chronic progression often compromises performance and quality of life. Eccentric training protocols, such as the Alfredson regimen, are commonly prescribed but their standardized nature does not fully address individual variability. Alternative approaches including Heavy Slow Resistance training and progressive loading models (e.g., Silbernagel protocol) have demonstrated clinical effectiveness and higher patient adherence, yet they still apply uniform loading across the triceps surae without accounting for architectural differences. Given the heterogeneous structure of the soleus and gastrocnemii, targeted loading strategies may be required to optimize tendon adaptation. To address this, the present study employs a muscle architecture-based exercise program tailored to the functional and structural properties of each muscle. Ultrasound imaging will be used to evaluate muscle-tendon morphology, while isokinetic dynamometry and functional performance tests will quantify outcomes. Pain (VAS) and functional capacity (VISA-A) will also be assessed. This randomized controlled trial aims to compare the effectiveness of an architecture-specific program with the Alfredson protocol on tendon remodeling, strength, endurance, functional performance, and symptom reduction in individuals with non-insertional Achilles tendinopathy.

Conditions

Achilles Tendinopathy (AT); Eccentric Exercise Training; Muscle Architecture; Isokinetic Test; Ultrasound; Balance; Anaerobic Power

Keywords

Achilles tendinopathy; muscle architecture; isokinetic strength; Alfredson protocol; tendon architecture

Outcome Measures

Primary Outcomes (7)

• Muscle Strength and Endurance - Cybex HUMAC/NORM Isokinetic Dynamometer

  Lower limb plantar flexor strength and endurance will be assessed using the Cybex HUMAC/NORM 2002 isokinetic dynamometer. Participants will be seated securely in the test chair, with trunk and pelvis stabilized by straps.The ankle joint will be aligned with the dynamometer axis at the lateral malleolus, starting in 0° plantargrade neutral. Range of motion will be set between 20° dorsiflexion and 30° plantar flexion, and participants will wear flat-soled shoes. Three test protocols will be applied: Soleus-dominant assessment: knee flexed at 80-90°, concentric mode, angular velocity 90°/s, 20 consecutive repetitions; outcome: peak torque (Nm) Eccentric-concentric assessment: knee extended, eccentric-concentric mode, velocity 90°/s, 3 maximal repetitions; outcome: peak torque (Nm). Combined gastrocnemius-soleus assessment: knee extended, concentric-concentric mode, velocity 180°/s outcome: peak torque (Nm).

  From enrollment to the end of treatment at 12 weeks

• Muscle and Tendon Architecture Measurements

  Muscle architecture of the medial and lateral gastrocnemius and soleus will be assessed with B-mode ultrasonography. Outcomes include fascicle length (cm), pennation angle (°), thickness (mm), cross-sectional area (cm²), and volume (cm³). Participants will be prone with standardized alignment; images will be acquired using a 5-12 MHz probe in longitudinal and transverse planes. Muscle thickness will be measured between aponeuroses, fascicle length measured directly or calculated, pennation angle determined from fascicle-aponeurosis intersection, CSA traced from transverse images, and volume calculated from serial CSA values. Image analysis will be performed using ImageJ. Achilles tendon will be evaluated with a 10-15 MHz probe in prone with slight knee flexion. Outcomes include tendon thickness (mm, 3 cm proximal to insertion), fibrillar organization scored qualitatively, and neovascularization graded via Power Doppler. All measurements will be obtained by blinded experienced examiner

  From enrollment to the end of treatment at 12 weeks

• Function - Victorian Institute of Sport Assessment-Achilles (VISA-A)

  The VISA-A is an 8-item, self-reported questionnaire specifically developed to assess symptoms related to Achilles tendinopathy. Scores range from 0 to 100, with higher values indicating better clinical status. The scale has been demonstrated to be a valid and reliable tool for evaluating the clinical severity of Achilles tendinopathy. The Turkish version (VISA-A-Tr) has also shown high test-retest reliability and acceptable internal consistency, confirming its suitability for use in this population.

  From enrollment to the end of treatment at 12 weeks

• Muscle Elasticity - Myoton PRO

  Muscle and tendon elasticity will be assessed with the MyotonPRO device in prone position with ankles in neutral. The probe applies a brief mechanical impulse, and five measurements per site will be averaged. Measurements will be obtained at the medial gastrocnemius, lateral gastrocnemius, soleus, and Achilles tendon. Separate outcomes will be reported for each parameter: frequency (Hz), stiffness (N/m), decrement (logarithmic), creep (µm/N), and relaxation time (ms). This method provides reliable and reproducible data on tissue mechanical properties.

  From enrollment to the end of treatment at 12 weeks

• Single Leg Forward Hop Distance (cm)

  Participants will stand on the test leg and perform a maximal forward hop, landing on the same leg with controlled balance. One practice trial will be allowed, followed by three valid attempts, with the longest distance in centimeters (cm) used for analysis. To be considered valid, participants must maintain balance for at least two seconds after landing. Contact with the opposite leg, instability, or multiple hops will invalidate the trial. Arm movement is permitted. Rest intervals will include 30 seconds between attempts and 2 minutes between tests. This test is applied to evaluate lower limb functional performance and inter-limb symmetry. Previous studies have demonstrated excellent reliability and low measurement error for this assessment.

  From enrollment to the end of treatment at 12 weeks

• Single Leg Stance Balance Time (seconds)

  Participants will attempt to maintain balance barefoot on one leg while standing on a firm surface. The outcome is recorded as balance duration in seconds (s). Movement of the test leg or ground contact by the contralateral leg invalidates the trial. Testing is performed under both eyes-open and eyes-closed conditions. Each leg is tested three times with up to 60 seconds per trial and 1-minute rest intervals. The best performance under each condition is used for analysis. This measure reflects static balance ability.

  From enrollment to the end of treatment at 12 weeks

• Ankle Mobility - Weight-Bearing Lunge Test

  Ankle dorsiflexion range of motion will be assessed using the weight-bearing lunge test. Participants will stand barefoot facing a wall in a lunge position with the test limb in front. Without lifting the heel, they will move the knee forward until it touches the wall, and the maximum distance from the wall to the tip of the great toe will be measured in centimeters with a tape measure. Each limb will be tested three times, and the best value will be recorded for analysis. A 30-second rest will be provided between trials. Standardized verbal instructions will be given, and pain will be monitored using the Numeric Rating Scale. This method is considered a valid and reliable measure of ankle dorsiflexion mobility.

  From enrollment to the end of treatment at 12 weeks

Secondary Outcomes (1)

• Pain - Numeric Rating Scale (NRS)

  From enrollment to the end of treatment at 12 weeks

Study Arms (2)

Alfredson protocol

ACTIVE COMPARATOR

Participants in this group will follow the classical Alfredson eccentric heel-drop protocol, widely used in the management of Achilles tendinopathy.

Other: Alfredson Protocol

muscle architecture-based exercise program

EXPERIMENTAL

Participants in this group will perform an exercise program tailored to the architectural properties of the triceps surae muscles. Positioning and loading strategies will be individualized to optimize activation of the soleus and gastrocnemii.

Other: Muscle Architecture-Based Exercise Program

Interventions

Muscle Architecture-Based Exercise Program OTHER

Participants in this arm will perform exercises specifically designed according to the architectural and functional properties of the triceps surae muscles. For example, knee-flexed positions will be used to target the soleus, while knee-extended positions will be emphasized for the gastrocnemii. Loading intensity and exercise progression will be tailored to optimize tendon and muscle remodeling.

muscle architecture-based exercise program

Alfredson Protocol OTHER

This intervention involves the traditional eccentric heel-drop program, originally developed for mid-portion Achilles tendinopathy. Participants perform three sets of 15 repetitions, twice daily, throughout the intervention period. Exercises are carried out both with the knee extended and flexed to load different portions of the triceps surae. The protocol applies repetitive eccentric loading to the Achilles tendon with the aim of stimulating collagen synthesis, reducing symptoms, and promoting tendon adaptation.

Alfredson protocol

Eligibility Criteria

• Age: 18 Years - 60 Years
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64)

You may qualify if:

• Presence of pain and tenderness in the mid-portion of the Achilles tendon (2-6 cm proximal to the insertion) persisting for at least 3 months
• Clinical diagnosis of non-insertional Achilles tendinopathy
• Pain aggravated by physical activity
• Palpable tenderness localized to the mid-portion of the tendon
• Voluntary participation in the study with signed informed consent

You may not qualify if:

• Diagnosis of insertional Achilles tendinopathy
• History of surgery or fracture in the affected lower limb within the past 12 months
• Corticosteroid injection to the Achilles tendon within the past month
• Presence of systemic diseases (e.g., diabetes mellitus, rheumatoid arthritis)
• Presence of neurological disorders (e.g., peripheral neuropathy, central nervous system disorders)
• Prior experience with eccentric exercise protocols targeting the Achilles tendon
• Acute onset of symptoms suggestive of a tendon rupture

Sponsors & Collaborators

• Halic University: lead
• Istanbul University: collaborator

Study Sites (2)

İstanbul University

Istanbul, Fatih, 34060, Turkey (Türkiye)

Location

İstanbul University

Istanbul, Fatih, 34060, Turkey (Türkiye)

Location

Related Publications (8)

• Al-Uzri, M., O'Neill, S., Watson, P., & Kelly, C. (2016). Reliability of isokinetic dynamometry of the plantarflexors in knee flexion and extension. Physiotherapy practice and research, 38(1), 49-57.

  BACKGROUND

• O'Neill S, Barry S, Watson P. Plantarflexor strength and endurance deficits associated with mid-portion Achilles tendinopathy: The role of soleus. Phys Ther Sport. 2019 May;37:69-76. doi: 10.1016/j.ptsp.2019.03.002. Epub 2019 Mar 9.

  PMID: 30884279 BACKGROUND

• Del Bano-Aledo ME, Martinez-Paya JJ, Rios-Diaz J, Mejias-Suarez S, Serrano-Carmona S, de Groot-Ferrando A. Ultrasound measures of tendon thickness: Intra-rater, Inter-rater and Inter-machine reliability. Muscles Ligaments Tendons J. 2017 May 10;7(1):192-199. doi: 10.11138/mltj/2017.7.1.192. eCollection 2017 Jan-Mar.

  PMID: 28717629 BACKGROUND

• Lauber B, Lichtwark GA, Cresswell AG. Reciprocal activation of gastrocnemius and soleus motor units is associated with fascicle length change during knee flexion. Physiol Rep. 2014 Jun 11;2(6):e12044. doi: 10.14814/phy2.12044. Print 2014 Jun 1.

  PMID: 24920126 BACKGROUND

• Kwah LK, Pinto RZ, Diong J, Herbert RD. Reliability and validity of ultrasound measurements of muscle fascicle length and pennation in humans: a systematic review. J Appl Physiol (1985). 2013 Mar 15;114(6):761-9. doi: 10.1152/japplphysiol.01430.2011. Epub 2013 Jan 10.

  PMID: 23305989 BACKGROUND

• Phillips B, Buchholtz K, Burgess TL. Gastrocnemius muscle architecture in distance runners with and without Achilles tendinopathy. S Afr J Sports Med. 2022 Jan 1;34(1):v34i1a12576. doi: 10.17159/2078-516X/2022/v34i1a12576. eCollection 2022.

  PMID: 36815930 BACKGROUND

• Beyer R, Kongsgaard M, Hougs Kjaer B, Ohlenschlaeger T, Kjaer M, Magnusson SP. Heavy Slow Resistance Versus Eccentric Training as Treatment for Achilles Tendinopathy: A Randomized Controlled Trial. Am J Sports Med. 2015 Jul;43(7):1704-11. doi: 10.1177/0363546515584760. Epub 2015 May 27.

  PMID: 26018970 BACKGROUND

• Alfredson H, Pietila T, Jonsson P, Lorentzon R. Heavy-load eccentric calf muscle training for the treatment of chronic Achilles tendinosis. Am J Sports Med. 1998 May-Jun;26(3):360-6. doi: 10.1177/03635465980260030301.

  PMID: 9617396 BACKGROUND

Central Study Contacts

Ömer Bayrak, Research Assistant

CONTACT

+905558826116; omer.bayrak16@icloud.com

Defne KAYA UTLU, Professor

CONTACT

+90 (530) 696 03 56; defne.kayautlu@sbu.edu.tr

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: SINGLE
• Who Masked: INVESTIGATOR
• Purpose: TREATMENT
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Research Assistant

Study Record Dates

• First Submitted: September 2, 2025
• First Posted: September 17, 2025
• Study Start: October 15, 2025
• Primary Completion (Estimated): December 15, 2026
• Study Completion (Estimated): December 31, 2026
• Last Updated: September 17, 2025

Record last verified: 2025-09

Locations

TU (2)