Muscle soreness (DOMS)

Delayed onset muscle soreness (DOMS) starts 12 to 24 hours after an unusual effort, peaks at 24 to 72 hours and fades within 5 to 7 days.

• It comes from micro-damage in muscle fibers after downhill running, a new intensity or more volume; it is not lactic acid, which clears within an hour.
• What helps a little: easy movement such as walking, massage or foam rolling, sleep, protein and carbohydrate.
• Keep sessions easy until it fades: hard efforts on very sore legs alter your stride.
• The repeated bout effect: the same session hurts far less the next time.

See a doctor if the pain is sharp or in one spot, the area swells, it lasts over a week, or your urine turns dark.