Ice Bath Science

Cold Water Immersion: The Physiology

Cold Water Immersion (CWI) involves immersing the body in cold water (typically 0°C-15°C for 5-10 minutes). This practice has been shown to trigger a series of physiological responses that contribute to a range of benefits. 

In the realm of wellness and performance, the practice of CWI has emerged as a scientifically supported method to enhance physical and mental well-being. Here we delve into the science behind using ice baths, including the potential benefits and limitations of CWI. 

1. Muscle Recovery and Reduced Inflammation:

Intense physical exercise leads to various physiological changes including muscle damage and hyperthermia. Hyperthermia is experienced when your body temperature is raised considerably above normal (not to be confused with hypothermia, occurring when your body temperature is below normal). After these physiological changes occur your body attempts to regain balance through the recovery period. An insufficient recovery period relative to the volume of training stress leads to overtraining syndrome, which is associated with regression or stagnation of progress.   

Hyperthermia typically leads to fatigue mediated by the central nervous system. CWI reduces cardiovascular strain and fatigue usually induced by the central nervous system. Studies have shown CWI to reduce tissue temperature and blood flow, thereby reducing the hyperthermic effect and subsequent post-training fatigue. Post-exercise cold water immersion is increasingly popular among athletes to minimize fatigue and speed up recovery. 

2. Improved Mental Well-being: The Neurochemical Impact

Depression is the leading cause of disability globally (World Health Organization) and, since the COVID-19 pandemic, anxiety and depression rates have increased 25% globally. There is an accumulating interest in cold water immersion as a treatment for depression, with multiple studies supporting its efficacy.

A study by Nikolai A Shevchuk hypothesised that one of the causes of depression was ‘A lifestyle that lacks certain physiological stressors that have been experienced by primates through millions of years of evolution, such as brief changes in body temperature (e.g. cold swim), and this lack of "thermal exercise" may cause inadequate functioning of the brain’.

This hypothesis was tested using cold water immersion performed 1-2 times per day. The results showed that CWI appears to activate the sympathetic nervous system and increase the blood level of endorphins, our feel-good hormones. In this way, cold water exposure can for many of us act as a natural mood enhancer. Further clinical trials, such as the study conducted by P Srámek on 'Human physiological responses to immersion into water of different temperatures,' found increases in plasma noradrenaline and dopamine concentrations post-cold water immersion.

Improvements in mental health are not gauranteed from cold water immersion, however, it offers an additional avenue to be explored along side traditional mental health treatments. Individuals may react differently to CWI so it is important to listen to your body and always consult a medical professional when necessary.

3. Increased Caloric Expenditure: A Thermogenic Boost

Brown adipose tissue (brown fat) is the body's principal defence against the cold, quickly producing heat to keep the body warm in a process known as thermogenesis. Regular cold water immersion has been shown to increase brown fat activation and in turn, raise metabolic rate. A study on ‘Human physiological responses to immersion into water of different temperatures’ by P Sramek found CWI to increase metabolic rate by 350%. Whilst CWI has also been shown to increase appetite, raising metabolic rate whilst maintaining caloric intake could be an effective method of maintaining a healthy weight. Incorporating regular cold water immersion into our daily routine can complement fitness goals and promote overall well-being.

4. Enhanced Immune Function: Unveiling the Body’s Defenses

An investigation into the effect of a noninfectious stimulus on the human immune system (L. Jansky) suggested that repeated cold water immersion lead to higher blood concentrations of T cells, which protect the body against infected cells. The study concluded a slight but significant improvement in immune system activity. 

While long-term cold water immersion may strengthen the immune system, there is short-term stress placed on the body. DO NOT engage in CWI with a weak immune system or underlying health conditions. Always consult a physician before undergoing cold water immersion.