Benefits of cold water
The Science & Use of Cold Exposure for Health & Performance
Safety
Never get into a dangerous body of water. Also, never do deliberate hyperventilation before or during cold water (or any water!) immersion. Start slow (warmer than colder)—as cold shock is possible; just as with lifting weights or other forms of exercise, you'll need to find the right temperature for you, yet prioritize safety.
How cold?
This is the most common question I hear, and it makes sense to ask that. However, it is truly impossible to answer, as some people tolerate cold better than others. The key is to aim for a temperature that evokes the thought, "This is really cold (!), and I want to get out, BUT I can safely stay in." For some people, that temperature might be 60°F, whereas for others, 45°F.
Here is the key: the colder the stimulus (water immersion, shower, etc.), the shorter amount of time you need to expose yourself to the cold. One study showed significant and prolonged increases in dopamine when people were in cool (60°F) water for about an hour up to their neck, with their head above water. Other studies describe significant increases in epinephrine from just 20 seconds in very cold water (~40°F). The good news is that as you do deliberate cold exposure more often, you will be more comfortable in the cold at all times and can start to use colder temperatures with more confidence, just like exercise.
Ice bath, cold shower, or cryo?
Most of the studies use ice baths or cold water immersion to the neck. Those are best, but cold showers can work too (and are more accessible to most). Cryo is very expensive and harder to access and not subject to much variation in protocols, so it is not considered here.
To Increase Energy and Focus
Deliberate cold exposure causes a significant release of epinephrine (aka adrenaline) and norepinephrine (aka noradrenaline) in the brain and body. These neurochemicals make us feel alert and can make us feel agitated and as if we need to move or vocalize during the cold exposure. Cold causes their levels to stay elevated for some time and their ongoing effect after the exposure is to increase your level of energy and focus, which can be applied to other mental and/or physical activities.
Building Resilience & Grit
By forcing yourself to embrace the stress of cold exposure as a meaningful self-directed challenge (i.e., stressor), you exert what is called 'top-down control' over deeper brain centers that regulate reflexive states. This top-down control process involves your prefrontal cortex – an area of your brain involved in planning and suppressing impulsivity. That 'top-down' control is the basis of what people refer to when they talk about "resilience and grit." Importantly, it is a skill that carries over to situations outside of the deliberate cold environment, allowing you to cope better and maintain a calm, clear mind when confronted with real-world stressors. In other words, deliberate cold exposure is great training for the mind.
Enhancing Your Mood
While not true of every stress, cold exposure causes the prolonged release of dopamine. Dopamine is a powerful molecule capable of elevating mood, enhancing focus, attention, goal-directed behavior, etc. Even short bouts of cold exposure can cause a lasting increase in dopamine and sustained elevation of mood, energy, and focus. Listen to Episode #39 to learn more about dopamine's role in the body.
Metabolism
In the short-term, cold exposure increases metabolism as the body has to burn calories to increase core body temperature. The total calories burned from the cold exposure are not that significant. However, the conversion of white fat (energy storage) to beige or brown fat (which are highly metabolically active) can be beneficial for:
- Allowing people to feel more comfortable in the cold (i.e., cold adaptation)
- Triggering further and more sustained increases in metabolism
Of course, calories in (consumed) versus calories out (metabolized) or "CICO" governs whether you gain, lose, or maintain weight. There is no escaping the laws of thermodynamics.
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