How long it takes to recover from a flash back depends on the patient’s specific situation and cannot be generalized. Flash back, also known as lumbar sprain, is mainly a violent force on the waist, resulting in acute strain of the lumbar muscles or small joint disorders of the waist. After the lumbar sprain will generally lead to sudden pain in the waist, the pain is more acute and more intense, the patient even appear activity restrictions, can not bend, walk, sneeze too hard will appear waist pain aggravated, seriously affect the patient’s life and work. At this time, the patient should immediately choose a hard wooden board to lie down and rest, and can apply local cold compresses. If the patient’s condition is mild, usually 3-5 days can significantly relieve the symptoms, if the patient’s condition is serious, usually need to treat about 2 weeks to recover. During the illness, patients are advised to avoid spicy foods in their diet, avoid drinking and smoking, and eat more fruits and vegetables rich in vitamin C to help promote recovery.