Cold exposure (and heat exposure) are hormetic stressors. Hormesis refers to a beneficial effect caused by exposure to low doses of a stimulus known to be toxic at higher doses. When applied properly hormetic stressors provide an adaptive stimulus that drives positive physiological changes.
Examples of hormetic stressors include:
Heat Stress – Sauna, Hot Water (whirlpool) and other
Cold Stress - the subject of this article
Muscular Stress in strength training
Cardiovascular Stress in cardio training
Fasting Stress - during extended periods with no calorie consumptions
Light stress like redlight, UV light stress, and Near Infrared Stress – yes these are actually low level stressors that initiate a beneficial adaptive response if not overdone!
Stress from beneficial plant chemicals which are often actually extremely small doses of plant toxins designed to prevent them from being eaten. For example, sulforaphane (the famous beneficial chemical from broccoli) is a plant toxin that stimulates your cells to increase their cellular defenses in response to this challenge!
Frequency/Intensity/Duration
Like exercise stress, the key is applying a particular stressor or set of stressors using the correct frequency, intensity and duration based on each person’s starting health and fitness and their desired goal! There is art and science to this process which is why trainers have a job!
These stressors all are part of our evolutionary heritage which helped shape our genetics over hundreds of thousands of years. Humans were exposed to all the stressors listed above routinely and if we had not developed adaptive responses to these stressors none of us would be here today!
As such these stressors actually turn on cellular defense mechanisms through an epigenetic response and this occurs very rapidly! Epigenetics refers to gene expression and is how the body responds to environmental cues and challenges – including exercise!
Exposure to these stressors – such as cold stress - immediately turns on the expression of cellular defense and anti-aging pathways in our cells.
The Scientific Research on Cold Exposure and Benefits
The vast majority of scientific research on Cold Exposure was done using cold water exposure not cryotherapy chambers (Cryo for short). This is not to say that Cryo cannot have benefits but there is much more research on Cold Water Exposure than Cryo! To take a deep dive on the research, mechanisms of action and benefits check out: https://hubermanlab.com/using-deliberate-cold-exposure-for-health-and-performance/ This a thorough review of the subject.
Another great site for information on this and other “biohacks” with real science is www.foundmyfitness.com
What happens when you do a cold plunge or take a cold shower?
When you do a cold plunge there is a massive increase in sympathetic nervous system activation corresponding with big increases in norepinephrine – aka noradrenaline which is the primary sympathetic neurotransmitter. Your sympathetic nervous system is sometimes called the “fight or flight” system. This is why you feel so awake and focused immediately upon cold water exposure. It is quite literally like turning on a light switch in your brain and nervous system.
There is also a big increase in Dopamine – the neurotransmitter behind motivation and drive.
Depending on how cold the water is and how long you stay in cold exposure will cause shivering as the body attempts to heat itself. This process is a big stimulus for the production of brown fat which actually burns white fat in response to a cold challenge. This is a powerful adaptive response that allows humans to survive periods of cold as our ancestors had to do on many occasions.
At the cellular level cells produce heat shock and cold shock proteins based on exposure to heat and cold. These proteins improve your cells ability to tolerate cold; protect against brain cell damage and inflammation; protect against cell death from oxidative stress; and speed up DNA repair.
Benefits of Cold Exposure
One of the biggest benefits is building will power and emotional resilience. When you do something you are resistant to every day you develop mental strength and discipline. Regular cold exposure will train you to be more resilient in the face of stress in your life in general. If you stick with it you will not only learn to tolerate it you will become used to it and be able to relax even in very cold water!
Another benefit is that your body can ramp up its innate production of antioxidants! When exposed to cold stimuli regularly the body increases glutathione, an antioxidant that helps keep other antioxidants performing at optimal levels in the body. A 1994 study found a drastic decrease in uric acid levels during and following the body's exposure to cold with a corresponding increase in glutathione. In this study cold water swimming measurably ramped up swimmers’ production of glutathione as an adaptive response to cold exposure!
Needless to say, an early morning cold shower or cold plunge will totally wake you up and increase alertness!
Cold Showers/Plunges can also improve skin and hair quality – cold causes increased blood flow to the skin after initially pushing blood into your core!
Cold Showers can help naturally increase Testosterone Levels and Boost Fertility – heat on male genitals definitely decreases testosterone production which is why the male genitalia are located outside of the body! Conversely cold increases testosterone production! A study at UCSF showed that men who stopped taking regular hot baths showed a sperm count increase of up to 491%.
Cold Exposure can also improve circulation – by increasing blood flow to your organs to keep them warm.
Cold Exposure can also improve immunity – studies have shown increased activation of white blood cells from cold exposure.
Cold showers can even potentially help relieve depression – they increase norepinephrine which is an excitatory neurotransmitter and there is even some research on this subject: https://www.ncbi.nlm.nih.gov/pubmed/17993252
Cold Exposure Improves Momentum - Cold plunging has shown the ability to increase your baseline dopamine. Dopamine is the molecule that is linked to motivation. Dopamine can enhance our depth of focus and lower our threshold for taking action towards our specific goals.
When to Use and NOT use Cold Exposure
The key time NOT to use a cold plunge is right AFTER resistance training exercise as it actually mitigates the positive adaptive response to strength training which requires an increase in oxidative stress and inflammation!
When doing a high intensity activity like weight training or HIIT training it is actually best to cold plunge BEFORE the activity! Why? Because cold exposure maximally activates the sympathetic nervous system resulting in better strength and HIIT workouts! Try it, the research clearly backs this up!
You can also use Cold Exposure on non-workout days! Many people find improved sleep with regular exposure to heat and cold stress.
Who Should NOT use the Cold Exposure?
Anyone with impaired circulation or hypersensitivity to cold such as people with Raynaud’s Disease
Angina or heart disease
Peripheral Vascular Disease
Epilepsy
Children
Geriatric Patients
Cold Urticaria
Cryoglobulinemia
Paroxysmal Cold Hemoglobinuria
Open Wounds
How Long and How Often for Cold Water Exposure?
Cold Water Immersion - If using cold water (anywhere from 40 - 50 degrees F) - start with a short session of 30 seconds and ideally gradually build up to 3 minutes. The key is to focus on slow even breathing – you will feel like you have to gasp but you can control your breathing by focusing on deep slow breathing. Through this process, you are learning to control your stress response and this pays big dividends!
The threshold for generating outstanding benefits from Cold Water Exposure is 11 minutes per week but there is no issue in going up to 15 – 20 minutes per week.
Cold Showers - Cold showers can provide similar benefits to cold water immersion particularly if you allow the water to hit your head and neck directly. Over the long term as you adjust you may actually find that the water does not get cold enough - particularly in summer months unless your shower water comes from a deep well that is always cold.
Cold Air Exposure - cold air exposure usually requires much lower temperatures and/or longer exposure times to provide the same stimulus because water pulls heat from the body much more efficiently than air. This is why cryotherapy chambers are usually from -140 to -250 degrees Fahrenheit! More and more cold therapy devices are coming out all the time including “dry” cold plunges and Cold Rooms/Boxes.
How to control intensity during Cold Water Exposure
There are two ways to control intensity:
Temperature Setting – a good temperature for beginners is 50 degrees Fahrenheit. Then over time you can drop the temperature down slowly to 45 or even into the high 30’s.
Surface Area Exposed - The other way to control intensity is by how you position your head, arms and hands – for maximum intensity put your whole arm and hands in the water and even dip down so your head is underwater for short periods – a whole new level when someone is ready for it!
Can You Mix Sauna with Cold Exposure?
Absolutely but for the best effect sauna first then wash off then finish with a cold shower! To get the absolute maximum from the sauna you will want to gradually build up to 20 – 30 minutes four days per week and 11 – 15 minutes of cold exposure each week. When you put both together the benefits are even greater!
