Effects of Strength Training on the Plantar Flexors' Properties After Achilles Tendon Rupture

NCT06912269 | Recruiting

• 1 other identifier: 6786944
• Study Type: interventional
• Target: 67
• Locations: 1 country
• Sites: 1

Brief Summary

Among the injuries that affect the Achilles tendon, rupture is one of the most frequent. This injury can generate functional, neuromuscular, and tendon deficits that can last for long periods or even be permanent. In the long term (i.e., more than a year after the injury), individuals present functional impairments related to the lower limb, deficits in the capacity to produce muscle force, as well as higher levels of muscle activation (as a compensatory response). Such changes may be due to injury adaptations in the plantar flexor muscles' architecture, which may have shorter, more pennate fibers, leading to reduced muscle thickness. Furthermore, the Achilles tendon may be elongated, with a greater cross-sectional area, presenting lower stiffness and quality (i.e., lower Young's modulus). Strength training can play an important role in recovering from Achilles tendon ruptures, as it promotes functional, neuromuscular, and tendon adaptations that can minimize deficits caused by the injury. However, there is a gap in the literature regarding strength training, as well as the dose vs response relationship, regarding functional, neuromuscular, and tendon adaptations after Achilles tendon rupture. Thus, the aim of the present study is to compare the effects of a strength training program of different intensities on plantar flexors' functional, neuromuscular, and tendon outcomes after Achilles tendon rupture. Men aged between 20 and 50 years old who suffered a total unilateral rupture of the Achilles tendon between one and five years after the rupture will be included in the study, as well as healthy men who did not suffer the rupture (control group). Participants who have suffered an Achilles tendon rupture will undergo a progressive lower limb strength training program twice a week for a total duration of 12 weeks, which will be randomized between two groups: low intensity (G55 - 55% of 1-RM) and moderate intensity (G70 - 70% of 1-RM). The following outcomes will be evaluated: a) Achilles tendon's morphological (length and cross-sectional area), mechanical (force-elongation relationship and stiffness) and material (stress-strain relationship and Young's modulus) properties; b) triceps surae muscles' morphological (architecture \[fascicle length, pennation angle and thickness\] and quality \[measured by echointensity and specific tension\]) properties; c) ankle functionality (maximum height in the heel raise test); d) the plantar flexors' force production capacity (peak and rate of torque development in different joint positions); e) the plantar flexors' muscle voluntary activation; and f) triceps suraes' neuromuscular capacity (i.e., recruitment curves). Assessments will be performed at two times (pre-training; and after 12 weeks of training \[post-12\]) through functional tests, ultrasound techniques, isokinetic dynamometry, electromyography, and percutaneous electrical stimulation. An intraclass correlation coefficient will be used to verify the test-retest reproducibility of ultrasound measurements. The Chi-Square test will be used to compare the level of physical activity (pre-training) between the groups. The results of the intervention will be expressed using descriptive statistics (mean, standard deviation, and standard error). The normality and sphericity of the data will be tested using the Shapiro-Wilk and Mauchly tests, respectively. A generalized estimating equation, followed by Bonferroni post-hoc, will be used to compare the effects of groups (G55 and G70) and times (pre-training, Post-6, and Post-12). A one-way ANOVA, followed by a Bonferroni post-hoc, will be used to compare the control group participants' limbs with the healthy and injured limbs from both intervention groups (G55 and G70) in the Pre and Post-12 times. The effect size will be estimated for each outcome. All statistical analyzes will be performed using SPSS software.

Conditions

Achilles Tendon Rupture; Strength Training Adaptations; Neuromuscular Adaptations

Keywords

Neuromuscular plasticity; Stiffness; Functionality; Triceps surae; Calcaneal tendon rupture

Outcome Measures

Primary Outcomes (5)

• Changes in foot and ankle joint function

  The foot and ankle joint function will be assessed through Foot and Ankle Outcome Score, which evaluate five different domains: pain, other symptoms, activities of daily living, sports and recreational activities, and quality of life related to the ankle and foot.

  From baseline measurements up to 13 weeks after (i.e., one week after the end of the training program)

• Changes in Achilles tendon function and symptom

  Achilles tendon post-rupture function and symptoms will be assessed through Achilles Tendon Rupture Score (ATRS).

  From baseline measurements up to 13 weeks after (i.e., one week after the end of the training program)

• Changes in ankle functional performance

  The ankle functional performance will be assessed using the heel raise test. With this test, the maximum height of the heel lift will be assessed, corresponding to the measurement of functionality of the ankle plantar flexors.

  From baseline measurements up to 13 weeks after (i.e., one week after the end of the training program)

• Changes in plantar flexors' muscle strength

  The plantar flexors' muscle strength will be assessed by the peak torque in different ankle joints (i.e., -10º, 0º, and 20º of plantar flexion - 0º neutral position).

  From baseline measurements up to 13 weeks after (i.e., one week after the end of the training program)

• Changes in Achilles tendon stiffness

  Tendon stiffness will be obtained by calculating the slope in the last 10% of the linear region of the force-deformation curve.

  From baseline measurements up to 13 weeks after (i.e., one week after the end of the training program)

Secondary Outcomes (5)

• Changes in Achilles tendon Young's Modulus

  From baseline measurements up to 13 weeks after (i.e., one week after the end of the training program)

• Changes in Achilles tendon morphological properties

  From baseline measurements up to 13 weeks after (i.e., one week after the end of the training program)

• Changes in plantar flexors' muscle arquitecture

  From baseline measurements up to 13 weeks after (i.e., one week after the end of the training program)

• Changes in plantar flexors' muscle activation

  From baseline measurements up to 13 weeks after (i.e., one week after the end of the training program)

• Changes in neuromuscular recruitment capacity

  From baseline measurements up to 13 weeks after (i.e., one week after the end of the training program)

Other Outcomes (2)

• Changes in plantar flexors' muscle power

  From baseline measurements up to 13 weeks after (i.e., one week after the end of the training program)

• Changes in plantar flexors' muscle quality

  From baseline measurements up to 13 weeks after (i.e., one week after the end of the training program)

Study Arms (3)

Strength training (low intensity)

EXPERIMENTAL

Twelve weeks of strength training program for the calf muscles, with low load intensity

Other: Exercise

Strength training (moderate intensity)

EXPERIMENTAL

Twelve weeks of strength training program for the calf muscles, with moderate load intensity

Other: Exercise

Healthy subjects

NO INTERVENTION

A control condition composed of healthy individuals (i.e., without any injury), who will not receive any training, will be used as a comparison at the beginning and end of the intervention.

Interventions

Exercise OTHER

A progressive calf strength training program lasting 12 weeks (twice weekly sessions), with a total of 25 visits to the gym. Specific exercises for ankle flexors: standing unilateral plantar flexion (on the machine) and seated unilateral plantar flexion (adapted on the Smith machine) will be performed. Participants will use progressive load from 55% of one repetition maximum load for the specific plantar flexion exercises.

Strength training (low intensity)

Eligibility Criteria

• Age: 18 Years - 64 Years
• Sex: male
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• Men aged 18 to 64 who have ruptured their Achilles tendon unilaterally no more than 5 years ago;
• Who are not performing systematic and regular calf strength training.

You may not qualify if:

• Non-surgical treatment for Achilles tendon rupture;
• History of postsurgical complications (infection or re-rupture);
• Presence of any type of ankle injury in the last six month;
• Participation in a strength training program for plantar flexors in the last six months prior to participation in the study;
• Having heart failure; autoimmune diseases; and/or diabetes;
• Systematic use of antibiotics or steroids within the last 12 months;
• Presence of any other clinical contraindication for performing maximum strength tests.

Sponsors & Collaborators

• Federal University of Rio Grande do Sul: lead

Study Sites (1)

Exercise Research Laboratory (LAPEX) - School of Physical Education, Physiotherapy, and Dance

Porto Alegre, Rio Grande do Sul, 90690-200, Brazil

RECRUITING

MeSH Terms

Interventions

Exercise

Intervention Hierarchy (Ancestors)

Motor Activity; Movement; Musculoskeletal Physiological Phenomena; Musculoskeletal and Neural Physiological Phenomena

Study Officials

• Jeam M Geremia, PhD

  Federal University of Rio Grande do Sul

  STUDY DIRECTOR

• Marcelo H Glänzel, MSc

  Federal University of Rio Grande do Sul

  PRINCIPAL INVESTIGATOR

Central Study Contacts

Jeam M Geremia, PhD

CONTACT

+5505133085852; jeam.geremia@ufrgs.br

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: TRIPLE
• Who Masked: PARTICIPANT, INVESTIGATOR, OUTCOMES ASSESSOR
• Purpose: TREATMENT
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Principal Investigator

Study Record Dates

• First Submitted: October 10, 2024
• First Posted: April 4, 2025
• Study Start: October 10, 2024
• Primary Completion (Estimated): August 20, 2026
• Study Completion (Estimated): August 30, 2026
• Last Updated: January 30, 2026

Record last verified: 2026-01

Locations

BR (1)