The Use of Cold Exposure to Promote Good Health

https://docs.google.com/document/d/1FyFtBnF0Y54WPYywqPaTxyPqx15i8anqtwJew72R9KQ/edit?usp=sharing

As the INSPIRE 2022 team successfully completed their expedition to the South Pole to explore the metabolic cost of sustained polar travel, those of us keeping a track of their journey through their social media channels were often in awe of just how much they were able to push their bodies each day in austere environments and freezing sub-zero temperatures. While not all of us will undertake an expedition in the South Pole in our lifetime, it is worth exploring the benefits of cold exposure and acclimatization in our day to day health outcomes.

The use of cold exposure to promote good health is an age old practice, dating back several centuries. Today cold exposure is primarily used by athletes to reduce muscle soreness and promote muscle recovery after intense physical activity. A meta-analysis of cold-water immersion effects on recovery found that cold exposure can be a highly effective recovery tool after high-intensity exercise or endurance training. The study showed that short intervals (<5 minutes) of cold water immersion led to positive outcomes for muscle power, perceived recovery and decreased muscle soreness - mostly due to a reduction in circulating creatine kinases.  Cold exposure is also shown to improve glucose and lipid metabolism, decrease inflammation, enhance immune function, and improve cognitive performance. These benefits may be in part due to hormesis -  a favorable biological response to a mild stressor. Hormesis triggers protective mechanisms that provide protection from future, more harmful stressors.

The INSPIRE 22 team set out on a mission to study the metabolic cost of sustained polar travel, but what does exposure to cold mean for our metabolism after all? In the short-term, exposure to cold can increase metabolism as the body has to burn calories to increase core body temperature. While the total calories burned from exposure to cold is not that significant, the conversion of white fat (energy storage) to beige or brown fat (highly metabolically active) is what helps the body adapt to cold and triggers a further and more sustained increase in metabolism. This is one of the main reasons why INSPIRE 22’s team was given the opportunity to spend time with the researchers at the Human Metabolic Research Unit in Coventry and their cold chamber. The team also had an opportunity to spend time in the cold chamber, practicing with equipment they would be using and putting up a tent in a simulated blizzard!

Be that an expedition in Antarctica or immersing yourself in an ice bath at home - cold exposure is an adventure that requires forcing oneself to embrace the stress of cold as a meaningful self-directed challenge. It is as much a mental challenge, as it is a physical one. Cold exposure, thus has tangible outcomes in developing resilience and grit. When we force a stressor like cold exposure upon ourselves, we exert ‘top-down control’ over the deeper brain centers that regulate reflexive states. This top down control process involves our prefrontal cortex - an area of our brain that is involved in planning and suppressing impulsivity. This top-down control is the scientific basis behind developing resilience and grit. As such it’s a skill that can be carried over to situations outside of the deliberate cold environment we expose ourselves to, allowing us to cope better with real-world stressors and maintain a calm and clear mind when confronted with uncomfortable situations. Simply put, deliberate cold exposure is a great training tool for the mind. 

When operating as a team in a unique extreme environment such as Antarctica there are inevitable pressures and strains – particularly with the relentless physical workload and mental focus required. While it sounds impossible to maintain focus amidst jaw numbing, subzero temperatures, deliberate cold exposure can actually cause a significant release of epinephrine - also known as adrenaline, and norepinephrine, also known as noradrenaline in the brain and body. These neurochemicals can make one feel alert and can also increase levels of energy and focus which can be applied to mental and/or physical activities that demand deep focus, alertness and elevated levels of energy. Cold exposure is also shown to cause a prolonged release of dopamine - a powerful molecule capable of elevating mood, enhancing focus and increasing attention and goal-directed behavior. 

While not all of us will take on an expedition across Antarctica in our lifetime, evidence suggests that exposing ourselves to a cold environment deliberately can have several positive health outcomes. As a rule of thumb, the environment should be uncomfortably cold, but one in which you can stay in safely. While the exact temperature will vary depending on your cold tolerance, core metabolism, and the 24-hour cycle of your circadian rhythm, it is recommended to not exceed 11-15 minutes of cold exposure per week. To optimize cold exposure for your health benefits, it is key to design protocols that are going to work for you over time and keep safety at the core of your practice.