Fig. 1

Hot pack treatment protocols for the experimental groups. a Treatment groups and time schedule of the treatment. Rats were divided into four groups: naïve control (CON), physical inactivity (PI), PI + sham, and PI + hot pack. b Photograph of casted hind limbs. Both hind limbs of rats in the PI, PI + sham, and PI + hot pack group were immobilized in full plantar flexed position using plaster casts for 4 weeks. c Photograph showing how hot pack was applied to rats. PI + sham and PI + hot pack groups were anesthetized with isoflurane and placed in a left lateral position on the hot pack and covered for 20 min a day, 5 days per week. d Daily protocol. Firstly, casts were removed from rats in the PI + sham and the PI + hot pack groups. Secondly, they received the sham or hot pack treatment. Next, their mechanical withdrawal threshold was examined. Finally, casts were put back on both hind limbs. In the PI group, the withdrawal threshold was measured after cast removal