Clinical trial NCT06912269: Effects of Strength Training on the Plantar Flexors' Properties After Achilles Tendon Rupture
Official title: Effects of Strength Training at Different Intensities on the Plantar Flexors' Functional, Neuromuscular, and Tendon Properties After Achilles Tendon Rupture
Study type: INTERVENTIONAL
Overall status: RECRUITING
Phase: NA
Conditions: Achilles Tendon Rupture
Strength Training Adaptations
Neuromuscular Adaptations
Keywords: Neuromuscular plasticity
Stiffness
Functionality
Triceps surae
Calcaneal tendon rupture
Lead sponsor: Federal University of Rio Grande do Sul
Sponsor class: OTHER
First posted: 2025-04-04
Enrollment: 67
Sex: MALE
Minimum age (years): 18
Maximum age (years): 64
Standard ages: ADULT
Accepts healthy volunteers: yes
Allocation: RANDOMIZED
Intervention model: PARALLEL
Primary purpose: TREATMENT

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.

Detailed description: 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.

Eligibility criteria: Inclusion Criteria:

* 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.

Exclusion Criteria:

* 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.

Primary outcomes:
measure: Changes in foot and ankle joint function
timeFrame: From baseline measurements up to 13 weeks after (i.e., one week after the end of the training program)
measure: Changes in Achilles tendon function and symptom
timeFrame: From baseline measurements up to 13 weeks after (i.e., one week after the end of the training program)
measure: Changes in ankle functional performance
timeFrame: From baseline measurements up to 13 weeks after (i.e., one week after the end of the training program)
measure: Changes in plantar flexors' muscle strength
timeFrame: From baseline measurements up to 13 weeks after (i.e., one week after the end of the training program)
measure: Changes in Achilles tendon stiffness
timeFrame: From baseline measurements up to 13 weeks after (i.e., one week after the end of the training program)
Secondary outcomes:
measure: Changes in Achilles tendon Young's Modulus
timeFrame: From baseline measurements up to 13 weeks after (i.e., one week after the end of the training program)
measure: Changes in Achilles tendon morphological properties
timeFrame: From baseline measurements up to 13 weeks after (i.e., one week after the end of the training program)
measure: Changes in plantar flexors' muscle arquitecture
timeFrame: From baseline measurements up to 13 weeks after (i.e., one week after the end of the training program)
measure: Changes in plantar flexors' muscle activation
timeFrame: From baseline measurements up to 13 weeks after (i.e., one week after the end of the training program)
measure: Changes in neuromuscular recruitment capacity
timeFrame: From baseline measurements up to 13 weeks after (i.e., one week after the end of the training program)
Other outcomes:
measure: Changes in plantar flexors' muscle power
timeFrame: From baseline measurements up to 13 weeks after (i.e., one week after the end of the training program)
measure: Changes in plantar flexors' muscle quality
timeFrame: From baseline measurements up to 13 weeks after (i.e., one week after the end of the training program)
Locations:
city: Porto Alegre
country: Brazil
facility: Exercise Research Laboratory (LAPEX) - School of Physical Education, Physiotherapy, and Dance
state: RS
Study officials:
affiliation: Federal University of Rio Grande do Sul
name: Jeam M Geremia, PhD
role: STUDY_DIRECTOR
affiliation: Federal University of Rio Grande do Sul
name: Marcelo H Glänzel, MSc
role: PRINCIPAL_INVESTIGATOR
References: