Highlights
- •Motor cortex Transcranial direct current stimulation (tDCS) accelerates the onset of exercise-induced hypoalgesia (EIH).
- •The effect of tDCS on EIH is not mediated by descending inhibitory pain mechanisms.
- •tDCS may be a promising adjunct treatment to exercise for pain management.
Abstract
Exercise-induced hypoalgesia (EIH) describes acute reductions in pain that occur following
exercise. Current evidence suggests that the magnitude of EIH is small-to-moderate
at best, warranting exploration of novel avenues to bolster these effects. Transcranial
direct current stimulation (tDCS) has been shown to relieve pain and represents a
promising intervention that may enhance EIH. This study aimed to determine whether
anodal tDCS of the primary motor cortex (M1) can augment EIH in healthy individuals
experiencing experimentally-induced musculoskeletal pain. Twenty-four healthy subjects
attended 2 experimental sessions (“Day 0” and “Day 2”). On Day 0, subjects were injected
with nerve growth factor into their right extensor carpi radialis brevis to induce
persistent elbow pain. On Day 2, each subject received active or sham tDCS over M1
followed by an isometric grip exercise. Pain intensity, muscle soreness, sensitivity
(pressure pain thresholds), and conditioned pain modulation were assessed prior to
the nerve growth factor injection, on Day 2 before tDCS, immediately post-exercise,
and 15 minutes post-exercise. Active tDCS expedited the onset of EIH, inducing immediate
reductions in pain intensity that were not present until 15 minutes post-exercise
in the sham group. However, active tDCS did not reduce muscle soreness or sensitivity
when compared to sham tDCS.
Perspective
These findings suggest that active tDCS accelerates the onset of EIH in healthy individuals
experiencing experimentally-induced pain. This may represent a promising means of
enhancing adherence to exercise protocols. However, larger randomised controlled trials
in persistent pain populations are required to confirm the clinical impact of these
findings.
Key Words
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Article info
Publication history
Published online: September 11, 2020
Accepted:
August 24,
2020
Received in revised form:
August 9,
2020
Received:
May 27,
2020
Footnotes
There are no conflicts of interest.
This research did not receive any specific funding from agencies in the public, commercial, or not-for-profit sectors.
Identification
Copyright
© 2020 by United States Association for the Study of Pain, Inc.
