The primary step in maintaining health and healing disease is to release musculo-skeletal holding patterns which are intimately related to more internal physical and their accompanying mental symptoms. This is the basis of healing.
Specific Yoga postures invigorate certain meridians. For example, backbends energize the yang aspect of the body, they generate heat and energy, while forward bends emphasize the yin or cooling, and calming aspects. If you feel sluggish or cold backbends will give you energy by stimulating the Kidneys . The Kidneys in Oriental medicine are the "root" of yin and yang. Also in Western scientific medicine it is understood that the Kidneys are the first organs formed in the fetus.
If you have insomnia or too much energy forward bends are more suitable because they have a soothing and calming effect emphasizing the yin aspects of the body. Right side bends and all twisting movements augment the liver and gallbladder while left side bends invigorate the spleen and pancreas
The complementary nature of yoga and acupuncture (and massage) is reflected in their common goal of releasing stagnation of energy in the meridian systems and their related organs or in the blood. While yoga provides the format to release the blockage acupuncture and meridian theory provides a framework to understand which poses are best for a particular condition. Additionally, herbs can tonify as well as unblock stagnation. Our overly fast lifestyles, combined with poor eating habits and a polluted environment can create deficiencies that herbs can help to correct. The Chinese pharmacopia is the largest, most advanced categorization of plants animals and minerals in all the world. It has withstood the test of time.
Thus, yoga. acupuncture and herbs help to balance the body and mind and create more consciousness towards the body's internal processes.
Invariably the poses you dislike to do the most are the best for you. The areas of weakness or decreased flexibility are usually places of stagnation in the meridian system. They are the most worthy of your attention and offer the most rewards upon investigation. For example, a person with poor digestion will almost always have weak abdominal muscles. Thus, properly performing asanas that emphasize the belly will move the energy of the low belly as well as strengthen the abdominal muscles and thereby help to alleviate the problem.
Similarly headaches and stagnation in the meridians of the muscles of the neck and shoulders can be alleviated by yoga because the postures circulate energy throughout the meridian system.
There is a saying in Chinese Medicine that is proven over and over again and the end of every yoga class, "When the mind is calm the qi flows smoothly, and conversely when the qi is made to flow smoothly the mind is calm". Isn't that why we practice yoga?