Medium- and Long-Term Effectiveness of Custom Insoles for Cavus Foot: A Surface Electromyography Study

Background: Cavus foot, defined by an increased medial longitudinal arch and often forefoot plantarflexion, alters biomechanics and increases peak plantar pressures, raising the risk of musculoskeletal disorders such as metatarsalgia, Achilles tendinopathy, and gait instability. Custom foot orthoses are the preferred conservative treatment, offering plantar support, pressure redistribution, and reduction in compensatory muscle activity. This study evaluated the medium- and long-term effectiveness of custom orthoses in 71 patients with cavus feet using surface electromyography (sEMG) and the same shoes. Methods: Muscle activity of the peroneus longus, peroneus brevis, and gastrocnemius was recorded during treadmill gait after one and four months of orthotic use. Results: Significant reductions in muscles were observed, especially after four months, confirming greater long-term effectiveness. No residual benefits were found when participants walked without orthoses. Conclusions: These findings support the clinical value of insoles in reducing the compensatory muscle activity in cavus feet and emphasize the importance of investigating their long-term role in biomechanics and potential pathology risk reduction.