Cheung, Hume & Maxwell 2003, Delayed onset muscle soreness

Sports Medicine review of delayed onset muscle soreness (DOMS). DOMS follows unaccustomed, especially eccentric, exercise; soreness appears around 12 to 24 hours afterwards, peaks at 24 to 72 hours and resolves within 5 to 7 days. The review attributes it to microscopic muscle and connective-tissue damage with subsequent inflammation, and argues against the lactic-acid theory on timing grounds (lactate clears within an hour or two, while DOMS peaks days later), though the paper concludes that an integration of theories is likely required. Soreness is a poor proxy for the size of the underlying damage. Exercise is the most effective means of alleviating pain during DOMS, though the relief is temporary; most other modalities give inconsistent or short-term symptomatic relief only.