Staying warm in winter the TCM way means keeping warm, avoiding the cold, getting plenty of sunlight, doing gentle exercise and eating yang (hot energy) foods.
According to traditional Chinese medicine, the major principle for health maintenance in winter is cang (storing) because yang keeps the body warm and active.
Sunshine is a major source of yang energy in the universe, and ancient TCM principles call for arranging one's schedule accordingly, with respect to sunrise and sunset.
Yang energy is consumed when people are awake and active and it is stored during sleep. Therefore, the first principle of storing energy is to get up late (or later than usual) and to go to bed early. One should wait for the yang-giving sunshine, according to "Huang Di Nei Jing" ("The Medical Classic of the Yellow Emperor"), the fundamental text of TCM.
As the sun rises later in winter than in other seasons, the idea is to get up no earlier than 7am. These ancient principles date from agrarian times when people lived closer to nature: Obviously modern people don't go to bed when the sun sets.
Anyhow, get plenty of sun (vitamin D) but don't get burned. A problem arises because sunblock prevents the body's production of vitamin D.
In addition to staying warm and wearing enough clothes, it's important to avoid pathogenic cold in winter, according to both the Yellow Emperor and Beijing TCM expert Zheng Guzhong, author of "Qiu Yi Bu Ru Qiu Ji" ("Better Refer to Yourself Than the Doctor").
Pathogenic cold (yin energy), which prevails in the universe in winter, can cause health problems. It can consume yang energy and obstruct the normal flow of blood and energy, resulting in pain. Blood vessels and tendons contract, which is unhealthy.
Wearing enough clothes is the easiest way to conserve yang energy, which defends the body against invasion of pathogenic cold. But yang energy is consumed by fighting the cold, so it's important to dress warmly.
The many young women who wear short skirts and short jackets in winter may be damaging their yang energy for the sake of fashion. Underneath their makeup, their complexion may be pale, bluish or dark. The cold slows blood circulation and may cause aching or numbness.
The head, back and feet are especially vulnerable to pathogenic cold, so it's important to keep them warm in winter.
Soaking the feet in hot (not too hot) water before bed warms both your system and your feet. The idea is to soak until there's a slight sweat; too much sweating is bad because it disrupts yang energy.
Getting sunshine (but shade your face) between 10am and 3pm can protect the head and back from cold. Light physical exercise in the sunshine is healthy, but if the temperature is below 2 degrees Celsius, it's best to wear a hat to conserve yang energy - otherwise yang energy is lost from the head.
Intense physical exercise that causes a heavy sweat should be avoided in winter, lest it consume too much yang energy that should be stored.
Tai chi, walking and simple stretching are good as they warm up the body but don't produce sweating.
Winter swimming is not suitable for everyone. Though swimmers don't sweat, weak people who swim may catch cold and cold water robs the body of yang energy.
It's best not to remove clothes during exercise until the body has warmed up; replace clothes after exercise. Sitting on a cold surface after exercising is unhealthy because pathogenic cold energy can invade from the bottom, travel through the back and reach the head, undermining organ health.