ISOMETRIC CONTRACTION-BASED PAIN MODULATION VERSUS ECCENTRIC STRENGTHENING IN TREATING ACHILLES TENDINOPATHY: A RANDOMIZED CLINICAL TRIAL

Background: Achilles tendinopathy is a degenerative condition of the Achilles tendon that leads to pain, impaired function, and reduced quality of life. Exercise-based rehabilitation remains the cornerstone of management, with isometric and eccentric protocols being widely prescribed. Although both approaches are commonly used, evidence directly comparing their effectiveness remains limited, particularly in controlled clinical trials. Establishing the superior exercise protocol is essential for developing evidence-based rehabilitation strategies to optimize tendon recovery and functional outcomes. Objective: The objective of this study was to evaluate and compare the effectiveness of isometric contraction-based pain modulation and eccentric strengthening in the rehabilitation of patients with Achilles tendinopathy. Methods: A single-blinded randomized controlled trial was conducted at a tertiary care hospital over six months, enrolling 42 patients (mean age 46.8 ± 6.6 years) diagnosed with Achilles tendinopathy confirmed by MRI. Participants were randomly assigned into two groups (n = 21 each). Group A performed an isometric contraction-based protocol, while Group B underwent Alfredson’s eccentric strengthening program. Both groups participated in six sessions per week for 12 weeks. Outcome measures included the Numeric Pain Rating Scale (NPRS), Victorian Institute of Sport Assessment–Achilles (VISA-A), and pressure algometry. Assessments were recorded at baseline, 6 weeks, and 12 weeks. Results: Both groups showed significant improvement over time; however, Group B demonstrated superior outcomes. Post-treatment median NPRS was 2.00 (IQR: 3.00–1.50) in Group B versus 5.00 (IQR: 5.00–4.00) in Group A (p = 0.000, rr = 0.876). VISA-A scores improved to 89.00 (IQR: 91.00–87.00) in Group B compared to 76.00 (IQR: 78.00–72.00) in Group A (p = 0.000, rr = 0.857). Pressure algometry increased to 6.00 (IQR: 7.00–6.00) in Group B versus 4.00 (IQR: 5.00–4.00) in Group A (p = 0.000, rr = 0.886). Conclusion: Both isometric and eccentric loading improved pain and function in Achilles tendinopathy, but eccentric strengthening provided greater pain reduction, enhanced functional recovery, and higher pressure pain thresholds. These findings support the preferential use of eccentric loading in tendon rehabilitation.