High-Definition Transcranial Direct Current Stimulation Enhances Exercise-Induced Hypoalgesia in Healthy Individuals: An fNIRS Study.

BACKGROUND

This study investigates whether anodal high-definition transcranial direct current stimulation (HD-tDCS) enhances exercise-induced hypoalgesia (EIH) and explores brain plasticity changes using functional near-infrared spectroscopy (fNIRS).

METHODS

Thirty-nine participants were randomly assigned to either the active (n = 19) or sham HD-tDCS (n = 20) group. Both groups performed 25 min of moderate-intensity aerobic exercise followed by 20 min of either active or sham HD-tDCS applied to the left primary motor cortex (M1).

PRIMARY OUTCOME: pressure pain threshold (PPT) at a local site.

SECONDARY OUTCOMES: PPT at a remote site, cold pain threshold (CPT), and brain activation changes via fNIRS during the cold pressor test.

RESULTS

Both groups showed significant increases in PPTleg (active: from 42.21 ± 11.77 N to 51.29 ± 12.75 N; sham: from 41.41 ± 9.73 N to 45.29 ± 12.05 N, p < 0.001) and PPTforearm (active: from 31.69 ± 6.06 N to 36.99 ± 6.35 N; sham: from 32.66 ± 7.34 N to 37.08 ± 10.56 N, p < 0.001). The active group showed a significantly greater increase in PPTleg compared to the sham group (9.08 ± 8.01 N vs. 3.69 ± 4.36 N, p < 0.012). fNIRS analysis revealed significant changes in specific cortical channels in the active group (p < 0.05), with a negative correlation between cortical activation in CH16 and PPTleg (r = -0.405, p = 0.011).

CONCLUSION

HD-tDCS over M1 enhances EIH and is associated with increased brain activation in sensory-motor processing areas.

TRIAL REGISTRATION: Clinical trial registration: ChiCTR2100048146.