Muscle Architecture vs Alfredson Protocol in Achilles Tendinopathy
NCT ID: NCT07178418
Last Updated: 2025-09-17
Study Results
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Basic Information
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NOT_YET_RECRUITING
NA
20 participants
INTERVENTIONAL
2025-10-15
2026-12-31
Brief Summary
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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.
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Detailed Description
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Conservative management is recommended as the first line of treatment, with the eccentric exercise protocol being the most widely used approach. Developed by Alfredson et al. (1998), this protocol consists of performing three sets of fifteen repetitions twice daily, aiming to stimulate collagen synthesis by mechanically loading the tendon. However, studies have shown that this protocol is not effective in every case; in some individuals, symptoms persist, and because the loading scheme is standardized, it fails to account for inter-individual variability. As an alternative, the Heavy Slow Resistance (HSR) exercise protocol, which includes both eccentric and concentric contractions, is applied three times per week. By incorporating controlled, high-resistance, slow-tempo loading, it aims to achieve functional recovery. Studies by Beyer et al. (2015) demonstrated that the HSR protocol yields clinical outcomes comparable to those of the Alfredson protocol, with higher patient satisfaction and compliance. In addition, the protocol developed by Silbernagel et al. (2007) incorporates both eccentric and concentric loading as well as functional activities in a more progressive model. By tailoring exercises to symptom tolerance during the acute and subacute phases and integrating plyometric activities such as hopping and jumping in the later stages, this protocol adopts a function-oriented perspective. Other conservative interventions, including extracorporeal shock wave therapy, cryotherapy, transverse friction massage, and footwear modifications, may provide symptomatic relief; however, their contribution to tendon remodeling is limited, and they do not ensure long-term structural or functional recovery. Although the Alfredson, HSR, and Silbernagel protocols are clinically effective, they carry significant limitations as they are not designed with muscle architecture-specific loading strategies.
The triceps surae muscle group exhibits heterogeneity in terms of architecture and function: the soleus muscle, with relatively short fascicle length, large cross-sectional area, and high pennation angle, contributes primarily to stability and endurance; the medial gastrocnemius is involved in both stability and controlled force generation; and the lateral gastrocnemius, with long fascicles and a narrow pennation angle, plays a key role in explosive force production. Despite these structural differences, both HSR and Silbernagel protocols apply a uniform loading strategy across all triceps surae muscles. For instance, optimal activation of the soleus requires the knee to be flexed, whereas activation of the medial and lateral gastrocnemius requires knee extension. Some existing protocols fail to consider such joint positioning, which may result in deviations from the optimal contraction axis, thereby reducing the effectiveness of muscle activation. This limitation may create uncertainty in the distribution of loading stimuli, hindering adequate tissue adaptation.
The muscle architecture-based exercise program to be implemented in this study is specifically designed in accordance with the architectural characteristics of each muscle, with the aim of providing the most optimal stimulus for each. Muscle and tendon architecture will be assessed using ultrasonography; strength outcomes will be measured with an isokinetic dynamometer; and functional performance will be evaluated through the Single-Leg Balance Test, Single-Leg Forward Hop Test, and Weight-Bearing Lunge Test. In addition, pain will be assessed using the VAS (Visual Analog Scale), and functional status will be measured with the VISA-A questionnaire. By conducting a comparative analysis, this study aims to evaluate the effects of architecture-based loading relative to classical protocols, thereby offering a novel perspective for treatment.
In light of this information, the present randomized controlled experimental trial has been designed to compare the effects of a muscle architecture-based exercise program with the classical Alfredson protocol on muscle-tendon architecture, muscle strength and endurance, functional performance, and symptomatic outcomes in individuals diagnosed with non-insertional Achilles tendinopathy.
Conditions
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Study Design
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RANDOMIZED
PARALLEL
TREATMENT
SINGLE
Study Groups
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Alfredson protocol
Participants in this group will follow the classical Alfredson eccentric heel-drop protocol, widely used in the management of Achilles tendinopathy.
Alfredson Protocol
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.
muscle architecture-based exercise program
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.
Muscle Architecture-Based Exercise Program
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.
Interventions
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Muscle Architecture-Based Exercise Program
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.
Alfredson Protocol
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.
Eligibility Criteria
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Inclusion Criteria
* 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
Exclusion Criteria
* 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
18 Years
60 Years
ALL
No
Sponsors
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Istanbul University
OTHER
Halic University
OTHER
Responsible Party
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Ömer Bayrak
Research Assistant
Locations
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İstanbul University
Istanbul, Fatih, Turkey (Türkiye)
İstanbul University
Istanbul, Fatih, Turkey (Türkiye)
Countries
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Central Contacts
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Facility Contacts
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References
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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.
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.
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.
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.
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.
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.
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.
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.
Other Identifiers
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Muscle Architecture
Identifier Type: -
Identifier Source: org_study_id
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