Sore Muscles and a fast easy Remedy Sore muscles (medically known as Delayed onset muscle soreness or "DOMS") is pain felt 24 to 72 hours after exercising and generally lasts 2 to 3 days. Once thought to be a build up in lactic acid, it is now thought that it is caused by tiny tears in the muscle fibers due to unfamiliar activity. It's typical symptoms include stiffness, swelling, strength loss and pain. The alternation between hold and cold is known to increase circulation as a treatment.