Delayed-onset muscle soreness (DOMS) is a normal response to unaccustomed or strenuous physical activity, often involving eccentric contractions (where muscles are stretched while contracted).
The typical trajectory of DOMS is no pain immediately after exercise but pain starting 12‒24 hours later. Pain usually peaks 1‒2 days after exercise but resolves within 7 days of onset.
Why is muscle soreness after exercising our arms and legs viewed as good... But muscle soreness after exercising our lower back viewed as bad?
Perhaps partly because of the common misconception that the back is more fragile and requires extra protection…
However, feeling back muscle soreness after back exercises (e.g., deadlifts and 45° back extensions) can be okay, much like sore quads after squatting or a sore chest after bench pressing.
Some episodes of back pain can be more than regular muscle soreness, but not all episodes of back pain are because of something serious or sinister.
If you’re unsure, consult with a health professional.