Muscle Architecture vs Alfredson Protocol in Achilles Tendinopathy

Not Applicable

Not yet recruiting

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

• Registration Number: NCT07178418
• Lead Sponsor: Halic University

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.

Detailed Description

Achilles tendinopathy is an overuse injury that develops as a result of repetitive microtrauma and is commonly observed in athletes as well as in sedentary male individuals. The clinical presentation is typically characterized by localized pain in the mid-portion of the tendon, tenderness, morning stiffness, and symptoms exacerbated by activity. Structurally, the condition is associated with tendon thickening, reduced echogenicity, and disorganization of collagen alignment . As the pathology becomes chronic, a marked decline in functional capacity is observed, which negatively affects both athletic performance and quality of life.

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.

Study Timeline

• Status Verified: 2025-09
• Study First Submitted: 2025-09-02
• Study First Submitted QC: 2025-09-10
• Last Update Submitted: 2025-09-10
• Study First Posted: 2025-09-17
• Last Update Posted: 2025-09-17
• Study Start: 2025-10-15
• Primary Completion: 2026-12-15
• Study Completion: 2026-12-31

Recruitment & Eligibility

• Status: NOT_YET_RECRUITING
• Sex: All
• Target Recruitment: 20

Inclusion Criteria

• 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

Exclusion Criteria

• 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

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: PARALLEL

Primary Outcome Measures

Name	Time	Method
Muscle Strength and Endurance - Cybex HUMAC/NORM Isokinetic Dynamometer	From enrollment to the end of treatment at 12 weeks	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).
Muscle and Tendon Architecture Measurements	From enrollment to the end of treatment at 12 weeks	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
Function - Victorian Institute of Sport Assessment-Achilles (VISA-A)	From enrollment to the end of treatment at 12 weeks	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.
Muscle Elasticity - Myoton PRO	From enrollment to the end of treatment at 12 weeks	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.
Single Leg Forward Hop Distance (cm)	From enrollment to the end of treatment at 12 weeks	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.
Single Leg Stance Balance Time (seconds)	From enrollment to the end of treatment at 12 weeks	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.
Ankle Mobility - Weight-Bearing Lunge Test	From enrollment to the end of treatment at 12 weeks	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.

Secondary Outcome Measures

Name	Time	Method
Pain - Numeric Rating Scale (NRS)	From enrollment to the end of treatment at 12 weeks	Pain intensity will be assessed using the 3-stage Numeric Rating Scale. Participants will rate their "worst pain," "least pain," and "current pain" experienced in the past 24 hours on a scale from 0 to 10. The mean of these three values will be recorded as the overall pain score. The NRS is a widely used, valid, and reliable tool for quantifying pain in musculoskeletal conditions.

Trial Locations

Locations (1)

İstanbul University; Istanbul, Fatih, Turkey (Türkiye)