From ‘Suwen – The Yellow Emperor’s Classic of Medicine’ translated by Maoshing Ni

(..) ‘The three months of spring season bring about the revitalisation of all things in nature. It is the time of birth. This is when heaven and earth are reborn. During this season it is advisable to retire early. Arise early also and go walking in order to absorb the fresh, invigorating energy. Since this is the season in which the universal energy begins anew and rejuvenates, one should attempt to correspond to it by being open and unsuppressed, both physically and emotionally.

On the physical level is good to exercise more frequently and wear loose-fitting clothing. This is the time to do stretching exercises to loosen up the tendons and muscles. Emotionally, it is good to develop equanimity. This is because spring is the season of the liver, and indulgence in anger, frustration, depression, sadness, or any excess emotion can injure the liver. Furthermore, violating the natural order of spring will cause cold disease, illness inflicted by atmospheric cold, during summer. (..)

‘With the arrival of spring the weather warms the earth. All plants begin to sprout and put forth green leaves, so the colour associated with spring is green. Since most fruits and trees are immature and unripe at this time, their taste is sour. This sour taste can strengthen the liver, and the liver can then nourish the tendons and tendomuscular channels. The wood element of the liver can produce the fire element of the heart; thus, it is said that the tendons produce the heart. Liver connects with the eyes through its channels, and thus it is said that the upper orifice of the liver is the eyes.

During spring the subtlety and vastness of the universe, the intelligence and intuition of the human being, the ability of the earth to produce the ten thousand things, the natural movement of the wind, and the upward motion of all plants, collectively produce the movement of the tendons, the colour green, the shouting of the voice, the spasms and convulsions, the eyes, the sour taste, and the angry emotions. These are all associated with the liver, since the liver is responsible for maintaining the potency of the flow of energy, and its nature is movement and expansion.

Anger can injure the liver, but sadness can relieve anger. When wind invades the dampness, it can injure the tendons, although dryness may eliminate the dampness and wind. Excessive consumption of sour foods can make the tendons flaccid, but this can be neutralised by the pungent taste. (..)