Time course of changes in range of motion, muscle shear elastic modulus, spinal excitability, and muscle temperature during superficial icing

Purpose The application of superficial icing has often been used in rehabilitation and sport settings. Some previous studies have shown that superficial icing or cooling increased range of motion and muscle stiffness. Considering that previous studies have investigated the effects of superficial icing only after 20 or 30 min, the superficial icing duration needed to increase range of motion has remained unclear. Moreover, another study showed that superficial icing increased spinal excitability, which could consequently increase muscle stiffness, although no study has investigated the relationship between change in muscle stiffness and change in spinal excitability after superficial cooling. The aims of this study was to determine the time required to increase range of motion by investigating changes over time during superficial icing and elucidate the mechanism whereby superficial cooling increased muscle stiffness by investigating the changes in muscle temperature and spinal cord excitability. Methods A total of 19 healthy volunteers participated in 2 experiments, the first of which sought to determine time-course changes in medial gastrocnemius muscle stiffness, dorsiflexion range of motion, passive torque at dorsiflexion range of motion during superficial icing and the second of which sought to investigate the time-course changes in spinal cord excitability in the dominant leg. Results and conclusion Our results showed that more than 5 min of superficial icing is required to increase range of motion, while the increase in muscle stiffness could be attributed to the decrease in muscle temperature and not change in spinal excitability.