The phenomenon described in Donguibogam as liver heat accumulating and stiffening the muscles can be explained in modern medicine in a way very similar to tension-type headache. Tension-type headache is a condition so common that 70 to 80 percent of the entire population experiences it at least once in their lifetime. It occurs through a combination of psychological factors such as stress, anxiety, fatigue, and sleep deprivation, alongside muscle tension caused by poor posture.
When our body experiences stress, the brain's hypothalamic-pituitary-adrenal axis is activated, increasing the secretion of stress hormones like cortisol. These hormones stimulate the sympathetic nerve, causing blood vessels to constrict, elevating heart rate, and triggering physiological responses that tighten muscles. In particular, the trapezius muscle, sternocleidomastoid, and suboccipital muscles around the neck and shoulders are muscles that respond very sensitively to stress. Continuous stress causes these muscles to contract and tighten chronically.
Muscles stiffened in this manner not only form trigger points on their own, but also compress the blood vessels and nerves passing through them, resulting in a circulatory disorder. The supply of oxygen and nutrients to the muscles drops, waste products accumulate, and muscular pain intensifies. This pain signal is transmitted to the brain via the cervical nerve, causing a disruption in the brain's pain modulatory system. Especially where the nuclei of the trigeminal nerve and cervical nerves connect, pain signals are amplified or distorted, leading to a headache perceived as constricting pressure across the entire head. The characteristic pain that feels like a tight band wrapped around the head or a heavy pressing sensation is precisely the result of this interaction between muscle tension and the nervous system.
Furthermore, chronic muscle tension leads to an imbalance in neurotransmitters involved in pain regulation, such as serotonin and norepinephrine in the brain. This lowers the pain threshold and causes one to feel more intense pain from even minor stimuli. In other words, stress tightens the muscles, tightened muscles trigger pain, and that pain increases stress again, creating a vicious cycle. All of these processes correspond remarkably well to the principle in Donguibogam where liver heat disrupts bodily balance and stiffens the sinews. It is now time to break this vicious cycle.
