There is only one benefit, and there are many disadvantages in promoting blood circulation. After the current passes through the human body, it can make the muscles contract and cause mechanical damage. The thermal and chemical effects produced by electric current can cause a series of sudden pathological changes and cause serious damage to the body, especially when electric current flows through the heart. Very small current can cause ventricular fibrillation, leading to death. The damage degree of electric injury to human body is related to the type, size, route, contact position, duration, health state and mental state of human body. 1, the greater the current passing through the human body, the greater the impact on the human body, so the higher the contact voltage, the greater the harm to the human body. Generally, voltages below 36 volts are considered as safe voltage. But in a particularly humid environment, even contact with 36V power supply is life-threatening, so in this place, 12V safe voltage should be used. 2. Alternating current is more harmful to human body than direct current, and alternating current with different frequencies has different effects on human body. The human body is much more sensitive to power frequency alternating current than direct current. When exposed to direct current, its intensity reaches 250 mA, which sometimes does not cause special damage. When it comes into contact with 50 Hz alternating current, as long as 50 mA current passes through the human body, if it lasts for tens of seconds, it can cause heart and ventricular fibrillation and lead to death. The current of 28-300 Hz in alternating current is the most harmful to human body, which is easy to cause ventricular fibrillation. Alternating current above 20000Hz has little influence on human body and can be used as physical therapy. The power frequency AC power supply we usually use is 50 Hz, which is reasonable from the point of view of designing electrical equipment. However, 50 Hz current is harmful to human body, so we must be vigilant and do a good job in safe use of electricity. 3. The duration of current is closely related to the degree of injury, and the short electrifying time has little influence on human body; If the current is energized for a long time, it will do great harm to the human body and increase the danger, especially when the current continues to flow through the human body for more than the heart cycle, it will pose a great threat to the heart and prone to ventricular fibrillation. 4. When the path of current passing through human body is different, the harm to human body is also different. The greater the current intensity through the heart, lungs and central nervous system, the more serious the consequences. Because different parts of the body contact with charged bodies, the current path through the body is different, so the current intensity flowing through different parts of the body is different, and the damage procedure to the human body is also different. Therefore, although the total current intensity passing through the human body is equal, different current paths have different consequences. 5. Current has the greatest influence on the heart.