Can ice baths improve health?

The exposure, in whole or in part, of the human body to cold temperatures is a practice that has been used for millennia by many cultures to relieve pain, control fever, accelerate recovery after physical exertion, and improve overall well-being. This ancient practice has gained popularity in recent years, particularly in the form of cold-water immersion (CWI), in which the body is partially or fully submerged in cold water, generally at temperatures ranging from 10 to 15 °C (Table 1). This technique has been routinely used for several years by athletes as a means of recovery after intense effort. More recently, CWI has become increasingly popular among the general population, an enthusiasm largely driven by various social media platforms promoting its many health benefits, both physical and mental. There remains, however, a wide gap between this enthusiasm for CWI and the limited amount of solid scientific data that would confirm these benefits. As we will see, even though the physiological responses of the human body to cold exposure are fairly well understood, the actual impact of these adaptations on health remains, for the time being, generally inconclusive.

Table 1. Main modes of deliberate exposure of the human body to cold temperatures. Adapted from Kunotsor et al. (2025).

Cold shock

It should first be noted that exposure to cold temperatures represents a stressful situation for the human body, leading to the rapid activation of several regulatory mechanisms aimed at counteracting this sudden drop in environmental temperature. During immersion in cold water (15 °C and below), cold receptors located beneath the epidermis respond to the abrupt decrease in skin temperature by causing:

• activation of the sympathetic central nervous system (SNS), characterized by a significant increase in plasma levels of noradrenaline and cortisol, two stress hormones;
• hyperventilation (which can lead to hypocapnia, i.e., an abnormally low level of CO₂ in the blood);
• an increase in cardiac output;
• peripheral vasoconstriction, to reduce external heat loss;
• an increase in blood pressure, caused by a reduction in surface blood flow that redirects blood toward internal organs.

Overall, the initial reactions to cold-water immersion place considerable strain on the cardiovascular system and may represent a threat for individuals with coronary artery disease, in whom a sudden increase in cardiac workload can cause myocardial ischemia.

These effects of cold water on cardiac function are particularly complex when the entire body is immersed, including both the head and the body (Figure 1). In this case, cold-water immersion activates two opposing autonomic nervous system responses: the diving response (triggered by facial immersion) and the cold-shock response (triggered by activation of cutaneous cold receptors). The diving response induces parasympathetic bradycardia (slowing of the heart rate), whereas cold shock induces sympathetic tachycardia (acceleration of the heart rate). It is hypothesized that these contradictory cardiac signals (sympathetic and parasympathetic) may, through complex mechanisms, create a “conflict” at the cardiac level when breathing resumes and trigger arrhythmias, particularly in the presence of various predisposing factors.

Adaptation to cold stress

It is, however, important to note that these negative effects of cold temperatures on the heart are very rare in healthy individuals. When the sympathetic nervous system becomes highly activated, as initially occurs during cold-water immersion, there is an immediate reflex activation of the parasympathetic nervous system to restore balance—that is, to slow the heart rate and reduce blood pressure (see our related article). According to several studies, this parasympathetic activation may even be globally predominant, as cold-water immersion appears to increase heart rate variability, one of the best indicators of parasympathetic activity. This is of interest insofar as increased resting parasympathetic activity has long been associated with better physical and mental health. The positive impact of cold-water immersion on the parasympathetic nervous system could therefore contribute, at least in part, to the beneficial effects on health and well-being attributed to cold-water immersion.

Athletic recovery

It is in the athletic context that cold-water immersion has been studied the most, particularly for its ability to accelerate recovery after exercise. A meta-analysis of 52 studies examining this question revealed that cold-water immersion after intense exercise can accelerate functional recovery, reduce muscle soreness, improve perceived recovery, and reduce post-exercise inflammation. It has also been observed that cold-water immersion accelerates activation of the parasympathetic nervous system in the minutes following intense exercise, thereby facilitating recovery.

However, other studies have shown that this ability to accelerate post-exercise recovery may have certain negative long-term consequences, particularly at the muscular level. For example, regular use of cold-water immersion after training sessions has been shown to blunt increases in muscle mass and the development of muscular power and strength. This effect of cold exposure is most likely due to a marked reduction (55–75%) in blood flow to the muscles, which prevents muscle cells from taking up sufficient amino acids from the bloodstream to synthesize new proteins.

Effects on overall health

As mentioned earlier, only a limited number of studies have examined the actual impact of cold-water immersion on health. A meta-analysis of 11 studies involving 3,177 participants  suggests some positive effects nevertheless, notably a reduction in stress 12 hours post-immersion, as well as improvements in sleep quality and overall quality of life. However, the magnitude of these presumed benefits remains difficult to quantify given the wide variability in experimental protocols used across studies.

It has also been proposed that exposure to cold water could strengthen immunity, an effect that is biologically plausible insofar as the stress response induced by a drop in temperature prepares the immune system to deal with injury or infection. However, research on the effects of cold-water immersion on immune function has produced mixed results, and it is still too early to conclude that cold-water immersion truly exerts beneficial effects on the immune system.

Based on current knowledge, the health benefits associated with cold-water immersion therefore appear to be mainly related to general well-being. Activation of the parasympathetic nervous system could play a role in this effect, as could the positive psychological (placebo) response generated by the pleasure experienced by individuals who enjoy the sensation of cold. It should be kept in mind nevertheless that cold water constitutes a shock to the human body, and it is strongly discouraged to immerse oneself alone, especially when immersion is performed in a natural environment (e.g., rivers, lakes, oceans). Cold-water baths may also pose dangers for individuals who suffer from (or have suffered from) heart disease because of the potential for arrhythmias triggered by thermal shock.