Transcranial direct current stimulation speeds up exercise-induced hypoalgesia

Transcranial direct current stimulation (tDCS) seems to accelerate the onset of exercise-induced hypoalgesia (EIH), leading to immediate pain reduction, a new study has found.

Twenty-four healthy adults participated in the study and attended two sessions. During the first session, persistent elbow pain was induced by injecting nerve growth factor into the participants’ right extensor carpi radialis brevis (ECRB). On the second session, participants received active or sham tDCS, followed by an isometric grip exercise. Pain intensity, muscle soreness, and pressure pain threshold (PPT) were among the study outcomes.

Following pain induction, participants in both the sham and active groups reported significant increases in numerical rating scale (NRS) scores during wrist flexion and extension (p<0.001 for both). A similar impact was reported on muscle soreness (p<0.001), while PPT over the right ECRB significantly decreased (p<0.001).

Active tDCS in combination with exercise resulted in significantly attenuated pain on wrist flexion (p=0.024) and extension (p=0.006) relative to the sham intervention.

In particular, NRS scores were significantly lowered for both actions immediately after exercise; by 15 minutes after exercise, the difference between groups was attenuated.

“These results suggest that active tDCS expedited the onset of EIH, but [it] did not necessarily bolster the magnitude of EIH once apparent,” the researchers explained.

In addition, active tDCS did not significantly impact muscle soreness or PPT at a local or remote site. Conditioned pain modulation, assessed as a change in the perceived pain in one body part as a response to a stimulus at another region, was also unaffected by tDCS.