Immediate Effects of Paraffin Wax Therapy on the Forearm and Hand Muscles' Stiffness and Pain in Patients With Carpal Tunnel Syndrome: A Randomised Controlled Trial

Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy of the upper limb and may alter the passive mechanical properties of forearm and hand muscles, contributing to pain and functional limitation. Handheld devices such as MyotonPro allow non-invasive, point-of-care assessment of muscle stiffness, elasticity and viscoelastic behaviour in clinical settings. Paraffin wax therapy is widely used as a superficial heat modality in hand rehabilitation and has been shown to reduce pain and improve function in various hand conditions, but its immediate effects on objectively measured muscle stiffness in CTS remain unclear. This parallel-group randomised controlled trial will examine the immediate effects of a single paraffin wax session on muscle stiffness and pain in adults with CTS. Physically active adults aged 18-65 years with clinically diagnosed CTS will be recruited from university-based facilities in Erzurum, Türkiye, and randomly allocated (1:1) to paraffin wax therapy or a control condition. A priori power analysis indicated that a total sample of 24 participants (12 per group) would provide adequate power to detect between-group differences in pre- to post-intervention change. Mechanical properties of selected forearm and hand muscles (e.g. APB, FDS, ECRB, FCU) will be assessed using MyotonPro immediately before and after the intervention. In the intervention group, the affected hand and forearm will receive 20 minutes of paraffin wax therapy at approximately 42-44 °C using a standardised brush-on technique and safety checks for skin integrity and temperature. Pain intensity in the affected region will be recorded pre- and post-session using a validated numeric rating or similar pain scale. The primary outcome is the between-group difference in immediate change in MyotonPro stiffness parameters, with secondary outcomes including change in pain and exploratory relationships between changes in stiffness and pain. Mixed model repeated measures ANOVA will be used to compare pre- to post-intervention changes between groups. Findings from this study may help clarify the short-term neuromuscular and symptomatic effects of paraffin wax therapy in CTS and inform future rehabilitation protocols.