Medical science believes that the speed of blood circulation throughout the body is inversely proportional to the speed of muscle movements. Tensions of muscles and nerves and compression of blood vessels will reduce blood flow and cause ischemia and hypoxia. When the increase is more than 60%, the local blood flow can be completely interrupted. Of all the diseases today, 60% to 80% can be traced from the current and excessive tension in life. What is this text is intended to illustrate? ['Modern medicine has found the root cause of most cases of disease today.', 'Excessive muscle and nerve tension is the main cause of vascular disease.', 'The speed of blood circulation is related to the tension of muscle and brain nerves.', 'Many diseases of modern people are related to stressful living conditions.']