The length of exercise per day needs to be decided according to different groups of people, types of exercise, and the condition of their own bodies. Weak people, should start with a short period of time, gradually increase the length of time, once the discomfort, such as panic, chest tightness, etc., should immediately stop exercise, and should be lighter physical activities, such as brisk walking, walking, etc., can take intermittent way, exercise for a period of time to rest a while. Physically strong people, exercise time can be properly extended to more than 40 minutes, within 2 hours, generally will not produce adverse effects, exercise types can also choose relatively more vigorous exercise, such as running, badminton, tennis, etc., but should also pay attention to moderation, should not be overly fatigued. According to the age group, young people can properly extend the time and increase the amount of exercise, while the middle-aged and elderly should reduce the amount of exercise. If walking, brisk walking and other light physical exercise is the main, exercise time can be maintained at 1-2 hours. If running, volleyball, tennis and other more strenuous sports are the main, it should be controlled at 30-60 minutes. Physical exercise has many benefits for the body, but attention should also be paid to avoid exercising in bright light; avoid drinking a lot of water after exercise, which increases the burden on the heart; avoid taking a cold shower immediately after exercise, which causes disorders in the organs of the body.