In rats, sore muscles after unusual exercise make a protein called NGF, which seems to cause pain sensitivity—blocking NGF quickly reduces soreness, and stopping another pain-related signal...

When you hurt a chewing muscle, your body might produce more of a protein called NGF, which could make the nerves in that muscle extra sensitive over time and lead to long-lasting pain.

In rats, sore muscles after unusual exercise seem to start with a specific pain signal (called bradykinin) turning on right when the exercise happens. If you block that signal before exercise, the rats don’t get sore — but only if you block it early.