This one is a no brainer… well… sort of.
We know that pain is a perceptual experience generated by the brain.
There’s no such things as pain receptors or painful stimuli in the periphery. Instead nociceptors send signals to the central nervous system regarding noxious stimuli, and the brain decides how that information will be perceived.
Some times it’s pain. Some times it’s not.
The mystery of delayed-onset muscle soreness (DOMS) is one of the those concepts thats been studied for decades with no real answers other than a process of elimination. For those of you who are still telling your clients that it’s “lactic acid” or whatever you’re making up today, perhaps you can now step up your game just a little bit.
Here’s a study that shows that the DOMS associated with eccentric loading is related to central sensitization of the nervous system. It’s also pretty clear that you don’t have torture your clients with muscle soreness either with a proper application of the repeated bout effect.