Hiccups are involuntary spasms of the diaphragm, the large, dome-shaped muscle beneath the lungs, followed by an abrupt closure of the glottis, which creates the characteristic “hic” sound. While often transient and self-limiting, persistent episodes can be highly disruptive. A specific, neuroscience-based method for interrupting this reflex has been popularized by neuroscientist Dr. Andrew Huberman, offering a targeted technique for quick resolution.
Understanding the Hiccup Reflex
The hiccup is a complex neurological reflex arc controlling muscle movement. The involuntary spasm of the diaphragm is triggered by signals traveling along a network of nerves, including the phrenic nerve and the vagus nerve. The phrenic nerve carries the motor command to the diaphragm, causing it to contract suddenly.
The vagus nerve and branches of the sympathetic chain act as the primary sensory input, relaying irritation signals from the abdomen and chest to the central nervous system. These signals converge at a reflex center within the brainstem, which coordinates the hiccup action. The resulting rapid, forceful inhalation effort against a closed glottis is the mechanical manifestation of this reflex loop.
The Huberman Hiccup Protocol
The recommended technique is a specific pattern of three sequential inhales designed to maximize lung volume and stimulate the relevant nerves. This approach begins with a full, deep inhale taken slowly through the nose.
Without exhaling, the individual must then take a second, brief inhale, pulling in more air to further expand the lungs. Immediately follow this with a third, even shorter intake of air, ensuring no air is lost between the three steps.
After achieving maximum lung capacity, the breath must be held for 15 to 20 seconds. This prolonged hold is an important component of the technique, creating a necessary physiological change.
The final step is a slow, controlled exhale through the nose or mouth, releasing the air gradually. If the hiccups persist after one attempt, the full sequence can be repeated until the reflex is successfully interrupted.
How the Technique Engages the Nervous System
The structured breathing pattern and sustained breath hold modulate the activity of the phrenic and vagus nerves. The multiple inhales followed by the breath hold rapidly increase the concentration of carbon dioxide (CO2) in the bloodstream.
An elevated level of arterial CO2 tension (PaCO2) is known to depress the hiccup reflex center in the brainstem. This hypercapnic state provides an overriding signal, which is more powerful than the irritating signal causing the hiccup.
Furthermore, the forceful expansion of the lungs and the subsequent breath-hold “hyper-excite” the phrenic nerve. This intense stimulation effectively fatigues the nerve, forcing it to relax and stopping the involuntary spasmodic contractions of the diaphragm. The combination of chemical signaling (CO2 increase) and mechanical nerve stimulation acts to reset the reflex arc.