Eli5: How do people not develop hyperthermia when participating in polar plunges?


Popular travel vloggers, known for their adventures around the world, visit Iceland in the winter and decide to take a polar plunge in a freezing cold glacial lagoon. Despite the shock of the icy water, they both manage to stay in for a short period of time and emerge unharmed. How do they manage to avoid developing hyperthermia?

In: 1

Hypothermia is usually the result of extended amounts of time exposed to extremely low temperatures. A quick dip in icy water won’t do that.

They often do, but it is still in the mild stages. You need to be submerged for close to 30 minutes for it to get concerning.

Hyper means increased, hypo means decreased. Assuming you meant hypothermic, the outside of the body can be cooled without its core temperature going down too much. A quick dip isn’t enough to cool all the body down. Blood vessels at the skin constrict to send less blood to the outside of the body for a short while, and muscles spasm or shake in order to warm up the insides of the body. If you notice when you get in cold water, you tend to tense up all the muscles, that’s the body’s way of increasing body temperature.

First off, you made a small error in your word. Hyperthermia is the body becoming too hot, hypothermia is the body becoming too cold. Hyper- as a prefix generally means higher than and hypo- means lower than.

The key to not getting hypothermia is the amount of time. Simple physics says that two objects that are in contact, but at different temperatures, will eventually equal out at a temperature between the starting two temperatures. On top of that, the body is designed to use energy to keep itself warm. Both of these combined mean a person has probably 30 min to an hour before problems would start to appear.

If you are shivering you’ve reached the first stage of hypothermia.

Hypothermia has three stages with the first being so mild people don’t even realize it.

The second and third stage are concerning and serious but it takes time to get there.

A brief dip in very cold water and then getting out and warmed up it’s a concern for the vast majority of people.

If they stated in the water they would quickly move through the stages and would die but that’s not the goal so they don’t stay in the water long enough.