This study will investigate whether a 12-week load-based exercise program performed with an externally rotated foot position ("toes-out") leads to different changes in intra-tendinous sliding, symptoms, and function compared to a standard exercise program performed with a neutral foot position in individuals with mid-portion Achilles tendinopathy. In addition, physical activity will be monitored during and after the intervention to examine how daily loading patterns relate to symptoms and functional recovery over a 6-month period.
Voluntary written Informed consent of the participant or their legally authorized representative has been obtained prior to any screening procedures.
Age between 18 and 65 years old
BMI between 18.5-30
Showing history of intermittent episodes of Achilles tendon pain lasting more than 3 consecutive weeks within the past 6 months.
None
Parallel
12-week adaptive, load-based exercise therapy protocol for Achilles Tendinopathy
Other interventionA 12-week progressive, load-based exercise program was developed, consisting of four daily exercises with gradually increasing tendon load over time. The program was based on the exercise battery and according Achilles Tendon loading index described by Baxter et al. (2021) and included a wide variety of 30 exercises (heel raise variations, step exercises, squats, lunges, jump variations, ...). A new exercise was introduced every four days, while weekly supervised sessions ensured correct execution and allowed for adjustments based on patient tolerance (e.g., excessive knee loading, too high pain scores during specific exercises, …). This flexible approach enabled gradual progression of each participant's daily load index according to individual capacity. An estimated time of 20-30 minutes daily is needed to execute all the daily exercises.
Intra-tendinous sliding between Achilles tendon layers (derived from ultrasound imaging and analyzed using a speckle tracking algorithm)
Ultrasound images of the Achilles tendon will be recorded using a probe (Hitachi L64, Tokyo, Japan) put in an external probeholder during multiple rehabilitation exercises: Birise Bidrop Standing, Unirise Unidrop Standing Knee Extended, Unirise Unidrop Standing Knee Bent and squat. The device we will use is the Arietta 650, FUJIFILM, which allows to record B-mode ultrasound images. The probe will be placed distally on the Achilles tendon, just above the calcaneal insertion (used as reference point). Using a speckle tracking algorithm in Matlab, the displacement of 6 rows within the Achilles tendon is calculated. Intra-tendinous sliding is calculated as the relative difference between the displacement of the superficial and deep border.
Clinical outcomes after Achilles Tendinopathy rehabilitation: Achilles Tendinopathy symptoms based on VISA-A questionnaire
At pretest, 3, 6, 9, posttest, 15, 18, 21, and 24, the VISA-A questionnaire will be completed online. During the pre- and post-test assessments, participants will complete the questionnaire on a laptop provided in the lab, ensuring it is administered online and in the same manner as throughout the intervention, where they fill it in at home. The VISA-A questionnaire is an 8-item survey used to assess the severity of Achilles tendinopathy. It evaluates pain, daily functional activities, and sporting ability, with scores ranging from 0 to 100, where a score of 100 indicates no symptoms.
Clinical outcomes after Achilles Tendinopathy rehabilitation: Achilles Tendon functionality based on heel-rise test
Heel-rise test: participants perform as many heel-raises as possible at a frequency of 25 per minute (controlled by a metronome). The test will be discontinued when the participant does not reach maximum height, cannot keep the frequency, cannot keep the knee straight or stops due to pain or fatigue. By using an application, the foot will be filmed and heel work will be calculated.
Clinical outcomes after Achilles Tendinopathy rehabilitation: Achilles Tendon functionality based on hopping till pain test
• Hopping till pain: the participant hops on a single leg at a pace of 2 jumps per second (controlled by a metronome) where the goal is to achieve 25 pain-free hops, but the test will be stopped when the participant starts to experience pain.
Questionnaire Data: Quality of Life (SF-12 questionnaire)
SF-12 questionnaire: used to assess health-related quality of life.
Doppler Vascularity
Intra-tendinous vascularity will be assessed in the sagittal plane with Doppler Ultrasonography (Arietta 650, FUJIFILM). The ultrasound transducer will be aligned parallel to the tendon and will be applied with no pressure and it will be positioned so that it visualizes the proximal portion of the calcaneal bone and the Achilles tendon. For this, participants will be in prone position with the knee extended and the ankle joint passively stabilized at 90°. Three scans with a duration of 4 seconds will be recorded at both the insertion and midportion of the tendon after all rehabilitation exercises in the lab are performed.
Morphological features of the Achilles tendon (free Achilles tendon length and volume)
During rest in the prone position, multiple scans of the lower leg will be acquired using 3D freehand ultrasound. This technique combines conventional B-mode ultrasonography (FUJIFILM Healthcare, Arietta 650DI) with a motion analysis system to generate in vivo three-dimensional reconstructions of tendon structures. The 2D ultrasound images will be transformed into a global coordinate system using the open-source medical image computing and visualization software 3D Slicer, enabling reconstruction of a 3D tendon volume. Based on this technique, the length and volume of the free Achilles tendon (AT) will be estimated. As a supplementary check, free AT length will also be measured manually by determining the distance between the calcaneal insertion and the soleus myotendinous junction, identified using ultrasound imaging. In addition, two ultrasound images (transverse and sagittal planes) will be obtained at the swollen region of the tendon to provide indications of tendon width.
Lower extremity biomechanics during rehabilitation exercises: kinematics, kinetics, muscle activations, muscle forces and cumulative Achilles Tendon load through musculoskeletal modeling (assesed with 3D motion and ground reaction force capturing)
In the lab, patients will perform four rehabilitation exercises: Bilateral heel raise-drop, unilateral heel raise-drop (knee extended and knee bent version) and squat. Besides that, walking and optionally (if the patient can) running on the treadmill. 3D-motion capture data, EMG (Delsys electrodes) and force plate data will be collected. Through musculoskeletal modeling in OpenSim, Kinematics, kinetics, muscle activations and forces (of Gastrocnemius medialis (GM) and lateralis (GL), soleus (SOL), tibialis posterior and anterior and peroneus) will be analyzed. Besides that, EMG will be recorded through Delsys electrodes on Gastrocnemius medialis and lateralis, soleus, tibialis anterior and peroneus. Achilles Tendon Load will be calculated as the sum of the tendon force from GM, GL and SOL from the musculoskeletal model - muscle analysis after dynamic optimization.
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KU Leuven
Lead sponsor
Universitaire Ziekenhuizen KU Leuven
Collaborator
