Huangdi Neijing mentioned that "people are born with the spirit of heaven and earth". A person can live for several weeks without food and several days without water, but he may suffocate for several minutes without air. Humidity, temperature, pressure, wind speed and negative ion content in the air have great influence on the body. Mild wind energy makes people relaxed and comfortable, and inhaling negative ions in the air can make people refreshed and endocrine coordinated, thus improving work efficiency.
In addition to air, the surrounding sunshine is also an important factor to help restore vitality. Just as plants can't live without sunshine, people will turn pale and get sick if they don't get sunshine for a long time. When the sun radiates the human body, it can cause thermal effect and photoelectric effect, and it can also act on the central nervous system with the help of skin receptors, thus regulating organ function and improving tissue metabolism. Ultraviolet radiation is the most beneficial to human health, is conducive to the synthesis of vitamin D, can prevent osteoporosis in middle-aged people, can directly kill bacteria and viruses, and enhance human immune function.
Water is the foundation of life, and it is also indispensable in health care. Water bath therapy has been highly respected since ancient times, and it is also a method of "rubbing bath" and "walking water stains" mentioned in Huangdi Neijing. In fact, everyone knows in daily life that bathing with hot water before going to bed can eliminate fatigue and help sleep; On the contrary, cold water can sober people up when they are in a bad mood.
Sunshine, air and water are only a part of nature. In fact, nature has brought us more than that. Proper use of these natural factors can improve the body's regulatory function, improve the body's adaptability to changes in the natural environment, and enhance physical fitness. Old people should actively use natural factors for exercise and fitness.