To solve the problems of complicated preparation process and poor intrinsic stretchability of existing stretchable electrodes,this study employs a simple in situ polymerization method and optimizes the dopant to develop a conducting polypyrrole-based fiber with excellent intrinsic stretchability.Sodium salicylate is utilized as both a dopant and a plasticizer during the fabrication process,resulting in a highly conductive fiber with an initial conductivity of 6.34 S/cm,which remains at 5.37 S/cm even under 100%strain.Furthermore,the elastic conductive fiber-based heater exhibits excellent Joule heating performance.When a 5 V voltage is applied,the surface temperature can reach 60 ℃,providing reliable heating effects for thermotherapy.Moreover,when integrating the conductive fibers into electric heating gloves,experimental results show that the surface temperature of the gloves only decreases by 4.89%during finger joint movements,enabling stable thermotherapy for moving joints.This provides a convenient and effective implementation for the physical treatment of conditions such as Raynaud's syndrome and joint injury pain.