Myth #18 — Sore Muscles Are Not Proof of Muscle Growth

Sore muscles feel like proof that a workout worked. A 2011 trial tested that directly. One group trained hard enough to show soreness and muscle damage; a second group was brought up gradually so it showed neither. Both did eight weeks of the same work, and both finished with the same gains in muscle size and strength. 1

Soreness is a poor stand-in for damage. A 2021 review of the soreness literature reports that pain ratings did not correlate with creatine kinase, a standard muscle-damage marker, in the trial it discusses, and that the link between soreness and ultrastructural injury was weak. 2

Soreness peaks on the first exposure to an unaccustomed movement and falls on repeat exposures to the same one. That protective response is called the repeated bout effect, catalogued in a 2026 review of the eccentric-exercise literature. 3 One trial had participants repeat identical eccentric sessions three weeks apart. The work performed was comparable, and strength and soreness both recovered faster after the second session. 4

Soreness is real, and unaccustomed or eccentric-heavy work reliably produces it. It can reasonably change what you do next session. It is just not a scoreboard. Log the load and the reps on your main lift, then beat that number next time.