What is Hormesis?

While higher doses of a stressor or situation can cause inhibition or toxic effects, lower doses can encourage adaptive compensatory processes, enhancing resilience. This is known as hormesis - a biphasic dose-response phenomenon in which exposure of a cell or organism to a low dose of a stress agent or condition stimulates adaptation & consequentially promotes physiologically beneficial effects. A hormetin can be condition or substance that may be potentially hormetic in physiological terms by activating or upregulating one or more cellular and molecular pathways of stress response that protect against a similar but more severe stress.

Benefits for the body

Cold shock is a type of hormetic stress that has been around for millenia. In the right doses, exposure to cold is enough to shock the body triggers a set of physiological and hormonal reactions that evolved millions of years ago to cope with a wide range of potential threats. This kick off some of these beneficial hormetic adaptive processes & response mechanisms that are evolutionarily hardwired into our genes helping us adapt to environmental change and ultimately cultivate resilience. But the cool thing about acute cold stress is the impact on the immune system - it can decrease inflammation. Just 20 minutes of cold elevates norepinephrine can rise 200-300% inhibiting inflammatory cytokines, known drivers of the inflammatory response. Your lymphatic system is activated by cold exposure, helping speed the clearance of toxins from tissues throughout the body. Cold also elicits enhanced anti-oxidative cellular defences including our internal anti-oxidant glutathione and superoxide dismutase pathway which improves immune cell function. Unlike low grade chronic inflammation, the inflammatory response that occurs immediately after exercise is actually productive, inducing the body’s repair mechanisms ensuring that you recover optimally and that your muscle heal and grow. If you interrupt your body’s pro-inflammatory response with cold therapy immediately after exercise, you may actually reduce the benefits from exercise and inhibit performance. Instead of icing right away, waiting about an hour post-exercise (aka after the peak pro-inflammatory process) may improve performance and recovery.

Benefits for the mind

Cold can increase the neurotransmitter norepinephrine which can lower pain & unruly inflammation & decrease levels of several inflammatory mediators, which unless you are fighting an acute infection, are unanimously beneficial for wellbeing. This neurotransmitter also plays an important role in focus and attention, vigilance and mood, which is why cold therapy has been trialled to treat depression & ADHD. Norepinephrine is also a hormone causing vasoconstriction, encourages mitochondria biogenesis in muscles - which improves endurance, encourages browning of fat cells - unlike white fat, which stores calories, mitochondria-packed brown fat cells burn energy and produce heat to help with regulating body temperature. Cold-therapy also somewhat activates Heat Shock Proteins, but not to the same extent as heat, which help untangle and assist with proper folding of cellular proteins. While reducing the unnecessary effects of unruly inflammation, we still want to have a robust stock of immune cells that function correctly. Consistent cold shock can increase immune cell numbers, in particular Cytotoxic T cells responsible for killing cancer cells & virally infected cells. It makes sense then that being a habitual sea swimmer decreases your probability of contracting a respiratory virus by 40%.

Broader benefits

It has also been shown that the stress resilience we obtain from cold-therapy benefits our response to different stresses such as exercising. This is called "cross-adaptation", where one form of stress adapts the body for another. There is increasing evidence linking depression and anxiety with the inflammation that accompanies a chronic stress response to the physical and psychological problems of modern life. Through cross-adaptation, cold water swimming may be able to reduce this chronic stress response together with the inflammation and mental health problems that affect so many of us. Exposure to cold can take many forms and getting cold is just one of them: from exposure to cold air temperatures, cold water immersion, sea swimming or ice-baths or just applying ice to specific areas of the body. But if you don’t have access to those, a toughing out a daily cold shower can work just as well! How cold do you have to get?

Let's look at some simple cold shock protocols:

Whole Body Cryotherapy (WBC) involves short exposure to extreme cold via a cryochamber – a human-sized tank filled with liquid nitrogen-cooled air. Exposure can vary from 2-3 minutes in temperatures that plummet to -130°C.
Another method is to take an ice bath (for up to an hour?!) in water temperatures of about 19°C.
Or if you live near water then just pop in for a weekly dip!
Or if none of these are accessible, just blast the cold water in the shower for as long as bearable before getting out.

Stacking hot & cold therapy?

Many people like to stack a stint in the sauna with a plunge into cold. We don’t know? But it seems to increase norepinephrine even more so perhaps synergistic.