Hardness of the abdomen may be caused by exercise, or acute appendicitis, gastrointestinal perforation and other diseases. 1. Exercise: If you often do flat support, supine get up and other exercises to exercise the abdominal muscles, may make the abdomen hard, usually no other discomfort, is a normal phenomenon. 2. Acute appendicitis: the occurrence of this disease is related to the obstruction of the appendiceal lumen, pathogenic microbial infections, appendiceal fecal stone, tumors and other causes. The main symptoms are abdominal pain, nausea, vomiting, etc. As acute appendicitis can cause muscle tension, even the symptom of plate-like abdomen may occur when perforation occurs. 3. Gastrointestinal perforation: the common cause of this disease is peptic ulcer, and it is also related to Crohn’s disease, stab wounds, intestinal infarction, poor dietary habits, and long-term use of large amounts of non-steroidal anti-inflammatory drugs and other causes. Patients will have hiccups, severe abdominal pain and other symptoms, while some patients will have the manifestation of abdominal muscle tightness. If the hardening of the abdomen is ruled out as a normal condition, you should go to the hospital in time to improve the relevant examination and clarify the specific causes.