There is mounting evidence that taking a brief and intense cold bath can result in both physiological and psychological benefits that are quite significant to our bodies. Thus, the most important aspect of this practice seems to be performing a cold exposure on a regular basis rather than pushing your own limits. A small amount of time spent in cold water daily is sufficient enough to adjust your body's stress response and improve your sleep-wake cycles. In this article we will discuss the intriguing science supporting a daily one minute cold bath as an effective way to build resilience in today's world, both physically and mentally.
Initially, the response to a sudden and extreme change in temperature (e.g. a cold shower) is to gasp for air, then your breathing rate becomes shallow and rapid. This is referred to as the cold shock response and is the body's primary method of responding to cold temperatures. There have been many studies written on this phenomenon, including articles in the European Journal of Applied Physiology, where extensive studies have demonstrated how the body reacts to extreme changes in temperature. The rapid decrease in the temperature of the skin sends a strong signal to the brain, which activates the sympathetic nervous system (fight or flight), resulting in an increased release of hormones (e.g. trigger for hyperventilation), and adrenaline (noradrenaline) and cortisol (increase in heart rate and blood pressure).This seems to be counterintuitive, as it may seem like an ineffective approach for reducing stress. The most important aspect of using cold exposure to decrease stress is that it is a temporary and controlled experience.
The stress caused by cold exposure is referred to as hormetic stress by many experts, meaning that it is a low-dose challenge that improves the body's ability to deal with stress. In contrast to psychological stress that causes long-term increases in the secretion of cortisol, the one-minute cold exposure creates a sharp but temporary peak of cortisol levels, which then decreases rapidly. Therefore, when repeated on a daily basis, this practice inoculates the body's autonomic nervous system and teaches the body a response to stress that is fast and energy-efficient, enabling it to recover quickly after a stressful event. This physiological training process has downstream benefits for daytime anxiety and nighttime sleep.
One of the most significant and well-supported findings in the field of cold exposure and perceived stress is the relationship between cold exposure and lower perceived stress levels. A key study conducted at the University of Portsmouth and other institutions demonstrated an adaptive response to cold-water immersion through biochemical changes in the body. With consistent practice, the initial noradrenaline spike will continue to provide a natural temporary boost of energy and an increase in focus. However, with continued practice, the cortisol spike will no longer be present and the body will learn to respond more appropriately to a stressful event.
This adaptation also has a significant effect on the limbic system (emotional control). Functional MRI studies indicate that cold exposure may increase the amount of grey matter in the prefrontal cortex, a brain area responsible for emotional regulation.The practice of taking Cold baths is also believed to stimulate the vagus nerve which is responsible for "rest and digest" activity of the parasympathetic nervous system. By regularly activating the vagus nerve through controlled breathing that occurs shortly after the initial gasp, the body increases vagal tone; higher vagal tone has been scientifically shown to correlate with improved emotional regulation, a quicker return to calm after an upset, and a greater sense of well-being, making individuals less reactive to day-to-day stressors.
There is an elegant biological explanation of how the cold bath can lead to deeper sleep. The idea that deep physiology and deep sleep are directly related is inevitable when you consider that the body's basal temperature must decrease to initiate and maintain the body's restorative stages of sleep. In terms of circadian rhythm, this is also an essential component of the body's ability to go to bed at night.
A warm bath taken in the hour or two preceding sleep will promote sleep by drawing warm blood to the surface of the skin, thereby decreasing core temperature.
A cold bath acts in a similar fashion that of a warm bath, in the opposite manner, but with greater thermal effect due to the process of what is called "rebound warming" or "afterdrop". Upon immersion in cold water, the body will attempt to retain its core temperature by constricting the blood vessels of the extremities. After exiting the water, the body overcompensates by dilating these blood vessels, causing warm blood to rush to the skin and extremities. The result is a significant redistribution of the excess heat from the extremities to the core, causing the core to continue to cool in subsequent hours after immersion.Research, including clinical studies published in sleep medicine journals, indicates that rapidly lowering body temperature in the evening helps individuals fall asleep more quickly and achieve longer periods of deeper, slow-wave sleep (SWS), which is the most restorative phase of sleep and necessary for physical recovery, consolidation of memories, and regulation of hormones.
In addition to regulating thermoregulatory processes, sleep benefits that stem from lowering core temperature are intermediately linked with stress relief through decreases in excess sympathetic nervous system activity and increased production of neurotransmitters involved with mood regulation (noradrenaline) and bodily pleasure production (endorphins) during the day. The reduction of mental "chatter" and anxious thoughts that inhibit sleep onset is derived through both mechanisms. In this way, insomnia is attacked from two different angles: by preparing the body's thermal environment for sleep and by quieting the mind that keeps the body awake and alert.
To adopt this practice, one must think in a mindful manner regarding how to approach it safelyand sustainably, taking into consideration the recommendations of authoritative sources, including studies conducted by the Extreme Environments Laboratory. The recommendation for exposure to cool water for one minute is an example of a safe, effective practice that is also very manageable for most individuals who are otherwise healthy. The goal of this practice is not to remain submerged in icy-cold water for a long time, but rather, to gain consistent exposure to short bursts of cold water.
As for temperature, the initial exposure can be set to a slightly cooler-than-normal water temperature (approximately 15 to 20 degrees Celsius [between 59 and 67.6 degrees Fahrenheit]) with an adjustment made as the individual becomes acclimated to the environment.
To use the cold-water conclusion method, simply turn the faucet to the coldest setting at the end of a normal shower routine. While maintaining your focus on the temperature, you should also concentrate on controlling your breathing at a steady, even pace, taking in/through the nose and exhaling out/through the mouth. This will help you to reduce the initial shock that your body may experience and stimulate the parasympathetic nervous system. As always, listen to your body during any environment-changing experience and consult a physician if you have heart or any other health-related issues that may be contraindicated to the use of exposure to cool water. The research indicates that the benefits of using this cold-water method accumulate and are associated with consistent use over time. When viewed in the light as a one-minute daily commitment (i.e., not overwhelming), this practice becomes an easily incorporated, manageable keystone habit, promoting a reduction in stress and improved quality of sleep from night to night.