What Happens to Your Body During a Cold Plunge?

Many people wonder what exactly happens in the body during cold plunging. In this article, we look at the most important physiological responses to cold exposure. When you begin cold plunging, you’ll likely notice these effects firsthand.

3 Primary Effects of Cold Plunging

During a cold plunge, three primary reactions occur in your body as a direct response to exposure to the cold.

1. Peripheral vasoconstriction
2. Chemical thermogenesis
3. Mechanical thermogenesis

Let’s take a closer look at each one.

1. Peripheral Vasoconstriction

This term may sound complex, but it’s something anyone who has frozen has probably experienced. The peripheral parts of the body (the parts of the body that are furthest away from your heart and therefore the most difficult to keep warm) are “sacrificed” by the body. This is a very natural and sensible defense mechanism, as it greatly increases your chances of survival. Instead of saving the entire body, only the most necessary parts with the most important organs are saved. And that doesn’t include your toes, feet, fingers, and hands.

• Everyday example: Cold hands or feet in winter.
• In a cold plunge: Hands and feet often ache or go numb within minutes.

The skin may also appear pale or bluish due to reduced oxygen and blood flow. While this is uncomfortable, short ice baths (1–3 minutes) are safe for most people.

Some cold plungers keep their hands out of the water or wear neoprene socks and gloves to reduce discomfort.

2. Chemical Thermogenesis

The first step is that the body decides to no longer keep all parts of the body warm, but only the vital organs in the center of the body. However, this alone is not enough, as the body must also try to boost heat production in order to warm itself up from the inside. This happens through biochemical processes such as the activation of the sympathetic nervous system. The cold activates the sympathetic nervous system, which promotes the release of neurotransmitters such as noradrenaline. These neurotransmitters act on various target organs and tissues to increase energy production and metabolism, which leads to increased heat production.

Here’s how it works:

• The body has two types of adipose tissue:
  • White fat: Energy storage
  • Brown fat: Heat-producing, rich in mitochondria

• In the cold, brown fat burns energy to generate heat, acting like tiny power stations inside your body.
• Children naturally have more brown fat to stay warm without shivering. Adults usually have less, but regular cold plunges can stimulate the development of new brown or beige fat.

Certain proteins, such as Uncoupling Protein 1 (UCP1), which is found in the mitochondria of brown adipose tissue, also support the process of thermogenesis. UCP1 is involved in the uncoupling of oxidative phosphorylation, whereby energy is generated in the form of heat instead of ATP (adenosine triphosphate).

3. Mechanical Thermogenesis

Also known as shivering, this is the body’s automatic response to cold. When your skin receptors sense a drop in temperature, they signal the hypothalamus in the brain. The brain then activates large muscle groups, especially in the core and limbs, to shiver rhythmically.

The trembling of the muscles generates frictional heat, as if you were rubbing your palms against each other. The heat is a by-product of friction.

Shivering requires significant energy to generate the friction force, which comes from:

• Carbohydrates for short-term fuel
• Fats (white fat stores) for longer-term energy

This increased metabolism not only warms the body but also burns calories: an added side benefit of cold plunging.

Conclusion

As you can see, your body is remarkably adaptive and resilient. And you need to treat it with the same care and attention. It can usually do more than you think. A short, well-timed cold plunge challenges your physiology in powerful ways; from protecting vital organs, to generating heat through fat metabolism, to burning energy via shivering. With regular practice, these responses strengthen over time, helping you become more resilient, energized, and adaptable to stress.