Why is he so cold-resistant? Because he is missing something...

Today we will talk about why some people are more resistant to cold in winter.

In the cold winter, in addition to wrapping in thick cotton clothes to keep warm, the human body also has its own "heating" device. When the cold receptors in the human body sense the drop in external temperature, they become excited and transmit signals to the hypothalamus. After that, the body temperature regulation center in the hypothalamus will transmit this signal to the parts of the human body responsible for heat production through nerve cells. For example, if you shiver from the cold, it is because the hypothalamus commands the skeletal muscles to tremble to increase heat production, and "goose bumps" on the skin are caused by the skin shrinking pores to reduce heat loss.

The human body's ability to resist cold is closely related to skeletal muscles.

The fibers of human skeletal muscle are mainly divided into two types: fast-twitch muscle fibers and slow-twitch muscle fibers. In daily life and exercise, fast-twitch muscle fibers are mainly responsible for explosive movements such as sprinting, high jump and long jump. They consume energy quickly and are easily fatigued. Slow-twitch muscle fibers are responsible for some aerobic exercises such as jogging. They are not easy to fatigue and have better tolerance to low temperature environments.

A 2021 Swedish study found that some people may be more resistant to freezing because something is wrong with their fast-twitch muscle fibers.

The researchers recruited 42 healthy male volunteers aged between 18 and 40, who usually did not do much physical exercise and whose jobs did not require them to stay in a cold environment for a long time. However, the "cruel" researchers asked the volunteers to soak in 14°C cold water for 20 minutes, then rest for 10 minutes, and repeat this process until their body temperature dropped to 35.5°C.

During the immersion process, the researchers used electromyography to monitor the electrical activity of the volunteers' muscles and assess their tremors. In addition, they collected muscle samples from the volunteers to test protein content and muscle fiber ratio.

The picture comes from Tuchong.com

The results showed that about 20% of the volunteers lacked a protein called "α-actin-3", which is only present in fast-twitch muscle fibers. When these volunteers took repeated "cold showers", their body temperature dropped very slowly and they did not shiver. About 70% of them could maintain a body temperature above 35.5℃ after contact with cold water. However, only 30% of normal people with this protein could maintain this body temperature after taking a "cold shower".

In other words, people who lack this protein in their skeletal muscles are more resistant to freezing than ordinary people. Researchers speculate that this may be because tens of thousands of years ago, when human ancestors migrated from the warm African continent to the north, a gene mutation occurred, allowing some people to acquire a more "freeze-resistant" attribute and better adapt to the cold climate in the north.

However, there are many organs in the human body that produce heat, and the extent to which skeletal muscle affects this requires further study. Swedish researchers also believe that the physiological mechanism proposed in this study has not yet been confirmed in molecular level experiments. In the future, they will continue to study and find the truth about why some people are "antifreeze".

This article is a work supported by Science Popularization China Starry Sky Project

Author: The Nutcracker

Review: Tao Ning

Produced by: China Association for Science and Technology Department of Science Popularization

Producer: China Science and Technology Press Co., Ltd., Beijing Zhongke Xinghe Culture Media Co., Ltd.