It is possible that the soreness of the lower back and legs is due to the following reasons: 1. It is possible that the lactic acid in the body accumulates after strenuous exercise and causes swelling and pain in the muscles of the lower back and legs, which usually disappears after 2-3 days of rest. 2. 3, may be caused by a lumbar disc herniation, in addition to the discomfort of the lumbar area will also cause nerve pull pain or soreness, numbness and other sensations to the muscles of the buttocks, thighs or calves.