Achilles Tendinopathy (AT) is characterized by pain, swelling and dysfunction. Rehabilitation strategies focus on conservative treatment, with eccentric exercise being the main and most popular option. Patient education based on the biopsychosocial model is considered important for effective self-management, including modification of activities and loads and pain monitoring. Established exercise protocols are applied in rehabilitation, with eccentric, eccentric- concentric combinations and high-resistance exercises performed at a slow pace being the most popular. The Pilates method , which has gained popularity in recent years, focuses on core stabilization, motor control, correct posture through respiratory patterns during execution as well as flow and mindfulness and is applied to the rehabilitation of various musculoskeletal disorders. Although there is a research background in rehabilitation, the data for its application in AT are limited. The present study aims to investigate the integration of Pilates into clinical practice for AT.

This study was designed as a pragmatic, parallel-group randomized controlled trial in individuals with Achilles tendinopathy. Participants were randomly allocated to either a Pilates-based rehabilitation group (intervention group) or an Alfredson eccentric loading group (control group) using a computer-generated random allocation sequence and sealed, opaque, sequentially numbered envelopes prepared by an independent researcher. Due to the nature of the interventions, participant and therapist blinding was not feasible. However, outcome assessment was performed by an assessor blinded to group allocation.

Different members of the research team were responsible for participant recruitment, randomization, intervention delivery, and outcome assessment in order to minimize potential bias and ensure allocation concealment. Participants were instructed not to disclose details of their intervention during outcome assessments. Adherence monitoring differed between groups according to the nature of the interventions. In the control group, participants received weekly follow-up communication and were encouraged to maintain adherence logs. In the Pilates group, adherence was monitored through supervised session attendance and rescheduling procedures when necessary.

Participants were recruited through referrals from healthcare professionals and public invitations for voluntary participation. Eligible participants were adults over 18 years of age with clinically diagnosed Achilles tendinopathy. Written informed consent was obtained prior to participation, and all participant data were pseudonymized using unique identification codes.

The intervention group followed an 8-week supervised Pilates-based rehabilitation program using Reformer equipment, with two 60-minute sessions per week and a 12-week follow-up assessment. The intervention incorporated progressive and individualized loading principles, motor control training, core stabilization, controlled movement execution, and functional progression according to symptom tolerance and participant performance.

The control group followed a 12-week modified Alfredson eccentric loading protocol. Participants performed a progressive home-based eccentric loading program involving exercises with the knee extended and flexed, adapted according to pain tolerance and symptom behavior. Weekly communication and monitoring were performed to support adherence and progression.

Outcome measures were collected at baseline and at 4, 8 and 12 weeks. Outcome assessment included patient-reported and functional measures evaluating pain, symptoms, kinesiophobia and functional performance in accordance with contemporary recommendations for Achilles tendinopathy assessment and the International Scientific Tendinopathy Symposium Consensus ICON/COS-AT framework.

An a priori sample size calculation using repeated measures ANOVA indicated that 128 participants would be required for adequate statistical power. Due to the pragmatic clinical design and recruitment feasibility, 49 participants were randomized and 45 completed the study. Statistical analysis was performed using repeated measures ANOVA to evaluate the effects of time, intervention group and time-by-group interaction across the assessment points. The study was designed primarily to evaluate feasibility, adherence, safety, acceptability and preliminary clinical response rather than to establish superiority between interventions.

Inclusion Criteria:

1. Men and women over 18 years of age with clinically diagnosed Achilles tendinopathy.
2. Ability to understand the study procedures and provide written informed consent.
3. Sufficient knowledge of the Greek language to complete the assessment procedures and questionnaires.

Exclusion Criteria:

1. Previous surgery involving the Achilles Tendon or ankle region
2. History of malignancy, systemic disease, neurological disorder
3. Chronic corticosteroid use or corticosteroid injection in the affected tendon region within the previous 4 weeks.
4. Participation in another exercise rehabilitation or conservative treatment program for Achilles tendinopathy within the previous 4 weeks.
5. Any condition limiting safe participation in an exercise-based rehabilitation program.

Individual participant data will not be shared due to privacy and data protection restrictions.