Dr. Andrew Huberman, Ph.D. is a Professor of Neurobiology and Ophthalmology at Stanford University School of Medicine. His lab focuses on neural regeneration, neuroplasticity, and brain states such as stress, focus, fear, and optimal performance.
In this episode of the Huberman Lab Podcast, learn all about breathing – the biology of respiration, nose versus mouth breathing, benefits of breath for mood, leveraging breath for improved health outcomes, types of breathing, and much more. 
Host: Andrew Huberman (@hubermanlab)
We breathe to bring oxygen in and remove carbon dioxide
  • It’s not as black and white as oxygen is good and carbon dioxide is bad
  • Breathing offloads carbon dioxide because excessive amounts are bad but we do need the correct ratios for bodily function
People who breathe too much put their bodies in a hypoxic state, with not enough oxygen to the brain
How breath moves in the body: air comes in through the nose and mouth; the larynx (rigid tube to avoid closing) brings air from the nose and mouth to the lungs
Lungs can expand and contract to bring in or expel air
  • Diaphragm is a muscle that moves the lungs
  • Intercostal muscles allow ribs to expand when air is brought in
Two brain structures control breathing: (1) the preBötzinger complex and (2) the phrenic nerve (motor nerve) from the neck which forms synapses with the diaphragm
Diaphragmatic breathing is the most efficient way of breathing: to test, inhale through the nose – if the belly moves out just a little, then goes in upon exhale, the phrenic nerve is controlling the diaphragm properly
The nose and mouth have different resistances to air
  • It’s normal one nostril is a little easier to breathe through at different points in the day (it’s not always because the septum is deviated)
At altitude: air pressure in the lungs is low and low outside is high so it takes more effort to get air into the lungs
Inhales tend to be active and exhales tend to be passive
Oxygen and carbon dioxide are needed by all the cells and tissues of the body but the ratio matters
Oxygen passes from sacs in the lungs (alveoli) into the bloodstream then gets bound by hemoglobin and is delivered to tissues in the body
  • Carbon dioxide is needed to liberate oxygen from hemoglobin
You want the body to be at about a pH of 7.4   
  • If carbon dioxide levels are too low, pH increases to make more oxygen available to tissues
  • When you exhale, carbon dioxide is taken from the bloodstream back into the alveoli of the lungs then out into the world through the mouth or nose
Carbon dioxide is a vasodilator
Sleep apnea: not taking deep enough or frequent enough breaths during sleep so experiencing hypoxic (not enough oxygen)
  • Symptoms of sleep apnea: excessive daytime anxiety, excessive daytime sleepiness, snoring
  • Dangers of sleep apnea: increases the risk of cardiovascular disease, and stroke, accelerates dementia, impacts cognitive function, decreases libido
  • Treatment options: CPAP machine, sleep with medical tape closing the mouth to force nasal breathing until trained, practice nasal breathing during exercise to transfer skill into sleep
Physiological sigh for relaxation and enhanced mood: 2 inhales through the nose (one big, one smaller) then 1 long exhale through the mouth until lunges are empty
  • A physiologic sigh can be cycled for 5 minutes or performed once for acute stress relief
  •  You can alleviate exercise cramps in right side using about 3 physiologic sigh – this specific cramp is related to misfiring in the phrenic nerve
  • Note, the cramp in the leftside is likely related to excessive air or fluid in the stomach (not alleviated by breathing)
When you hyperventilate you are inhaling and exhaling more than usual – this can increase anxiety in a reciprocal way, which deploys adrenaline and increases excitability
  • There’s a reduction in oxygen delivered to the brain and neurons increase firing so noise goes up and the signal goes down
Cyclic hyperventilation: deep inhale through nose immediately followed by deep exhale through mouth x 25-30 then fully exhaling until lungs are empty and repeating – cycle for 5 minutes
  • Do not do this in or near water because this may trigger a gasp reflex
  • This will increase adrenaline and is a way of inducing self-induced stress and allows you to explore how to tap into a calm mind and body during stressful times
  • Be careful doing this if you are prone to panic or anxiety attacks  
Most people breathe too much per minute – increase efficiency by nasal breathing and pay attention to how quickly you breathe and the amount of time between breaths
Use rhythmic breathing to calm the brain and body during physical stressors such as cold plunge
Hiccups are a spasm of the phrenic nerve
  • To reliably alleviate hiccups: inhale through the nose 3x in a row, hold your breath for 15-20 seconds, then exhale completely
The brain actually functions better when inhaling through the nose – you can increase memory retrieval, and cognitive function, block out signal-to-noise, detect novel stimuli
Carbon dioxide tolerance is an indicator of whether the system as a whole is working properly and measures the ability to mechanically control the diaphragm
  • Step 1: Inhale through the nose and exhale all the way – repeat 4x
  • Step 2: Take 5th inhale as deep as you can, release as slowly as possible, and time
  • Step 3: Stop the timer when you can no longer exhale any more air
  • If carbon dioxide discard time is 20-25 seconds or less, you have a low carbon dioxide tolerance
    • To improve, try 3-second box breathing: 3-second inhale, 3-second hold, 3-second exhale, 3-second hold, repeat about 2 minutes
  • If it took 25-45 seconds to discard air, you have a moderate level of carbon dioxide tolerance
    • To improve, try 5-6 second box breathing: 5-6 second inhale, 5-6 second hold, 5-6 second exhale, 5-6 second hold, repeat about 2 minutes
  • If you go 50+ seconds to discard until your lungs empty, you have a high carbon dioxide tolerance
    • To improve, try 8-10 second box breathing: 8-10 second inhale, 8-10 second hold, 8-10 second exhale, 8-10 second hold, repeat about 2 minutes
Box breathing will improve mechanical control over breathing; once box breathing becomes easy, try the carbon dioxide tolerance test again
  • Progress leads to deeper and less frequent breathing at rest
Carbon dioxide does not necessarily correlate to fitness but if discard time drops over time, you might not be putting enough energy into recovery
Carbon Dioxide Tolerance Clip (Galpin Guest Series Episode 3)
When you inhale, the diaphragm moves down and when you exhale diaphragm moves up
During inhale: the heart temporarily expands and blood moves slower which prompts neural signal to increase the heart rate
During exhale: the volume of the heart is reduced and blood flow accelerates which sends a signal from the nervous system to slow the heart rate
To quickly reduce or increase heart rate for a situation, you can take advantage of breathing
To increase heart rate: inhale longer and more deeply than exhales; to decrease heart rate: exhale longer and more vigorously than inhales
Box breathing will moderate heart rate to equilibrium
Tummo or Wim Hof style breathing: this is basically rapid, deliberate hyperventilation – this will make you feel alert and liberate adrenaline
Concentration of carbon dioxide, interstitial pH and synaptic transmission in hippocampal formation of the rat (Journal of Physiology)
Effects of voluntary hyperventilation on cortical sensory responses Electroencephalographic and magnetoencephalographic studies (Experimental Brain Research)
Brief structured respiration practices enhance mood and reduce physiological arousal (Cell Reports Medicine)
Breathing Rhythm and Pattern and Their Influence on Emotion (Annual Review of Neuroscience)
Nasal Respiration Entrains Human Limbic Oscillations and Modulates Cognitive Function (Journal of Neuroscience)
Effect of breathwork on stress and mental health: A meta-analysis of randomised-controlled trials (Scientific Reports)
Jaws: The Story of a Hidden Epidemic by Sandra Kahn